chore: move to @cozy-games/mnswpr

Reviewed-on: https://git.ayo.run/ayo/cozy-games/pulls/1
Co-authored-by: Ayo <ayo@ayco.io>
Co-committed-by: Ayo <ayo@ayco.io>

.gitignore

@@ -1,14 +1,14 @@
 node_modules/
 dist/
 
-# generated at publish time from the root README.md (see scripts/publish-lib.js)
+# generated at publish time from apps/mnswpr/README.md (see scripts/publish-lib.js)
-lib/README.md
+packages/mnswpr/README.md
 
 .claude
 
 # Production / local Firebase config values are not committed — set them as
 # Netlify env vars, or keep them in a local, gitignored env file. Dev values
-# live in the committed app/.env.development (public, non-secret keys).
+# live in the committed apps/mnswpr/.env.development (public, non-secret keys).
 .env.production
 .env.local
 .env.*.local
@@ -22,3 +22,6 @@ ui-debug.log
 *~
 *swo
 *swp
+
+# TEMPORARY - or unnecesary if done
+apps/mnswpr/MIGRATION.md

.husky/pre-commit

@@ -1,2 +1,11 @@
 echo "pre-commit..."
 npm run lint
+
+# Secret scan of staged files — blocks committing tokens, private keys, or a
+# stray .env.production before it ever reaches history. Config: .secretlintrc.json
+# / .secretlintignore. Full-tree scan: `pnpm run scan:secrets`.
+staged=$(git diff --cached --name-only --diff-filter=ACM)
+if [ -n "$staged" ]; then
+  echo "secret-scan (staged files)..."
+  printf '%s\n' "$staged" | xargs -r -d '\n' npx secretlint --secretlintignore .secretlintignore
+fi

.secretlintignore

@@ -0,0 +1,5 @@
+# Paths secretlint should not scan (vendored, generated, or lockfiles).
+node_modules
+dist
+pnpm-lock.yaml
+*.log

.secretlintrc.json

@@ -0,0 +1,7 @@
+{
+  "rules": [
+    {
+      "id": "@secretlint/secretlint-rule-preset-recommend"
+    }
+  ]
+}

AGENTS.md

@@ -4,37 +4,90 @@ Guidance for AI coding agents working in this repository.
 
 ## What this is
 
-Classic Minesweeper as a vanilla web game — no framework, no TypeScript (JSDoc + `// @ts-check` only). Deployed at [mnswpr.com](https://mnswpr.com) (Netlify) and published to npm as `@ayo-run/mnswpr`. The game engine has **zero runtime dependencies**; only the website adds Firebase.
+Classic Minesweeper as a vanilla web game — no framework, no TypeScript (JSDoc + `// @ts-check` only). Deployed at [mnswpr.com](https://mnswpr.com) (Netlify) and published to npm as `@cozy-games/mnswpr`. The game engine has **zero runtime dependencies**; only the website adds Firebase.
+
+**`mnswpr` is the main test app.** It's the reference app for the monorepo and the default target for local runs — `.claude/launch.json` launches it (`dev` on :5173, `preview` on :4173), and it's what you should build/run/preview when verifying changes to the shared packages or tooling.
 
 ## Commands
 
+Workspace-wide commands run from the root; per-app commands target the app by name with pnpm's `-F` filter (apps are named `<name>` — there are no mnswpr-specific root scripts).
+
 ```bash
 pnpm i              # install (pnpm is required — this is a pnpm workspace)
-pnpm dev            # run the website dev server (vite app) — most common
-pnpm build          # build the website  -> app/dist
-pnpm build:lib      # build the publishable library -> lib/dist
-pnpm lint           # eslint . (JS + CSS); runs automatically on pre-commit
-pnpm lint:fix       # eslint --fix
-pnpm build:preview  # build the app and serve the production preview
 pnpm test           # run the Vitest suite once (jsdom)
 pnpm test:watch     # run Vitest in watch mode
+pnpm lint           # eslint . (JS + CSS); runs automatically on pre-commit
+pnpm lint:fix       # eslint --fix
+pnpm build:lib      # build the publishable library -> packages/mnswpr/dist
+
+pnpm -F mnswpr run dev            # Firestore emulator + auto-seed + dev server (emulators:exec) — most common; needs JDK 21+
+pnpm -F mnswpr run dev:no-db      # plain vite, no emulator (UI-only work / no JDK)
+pnpm -F mnswpr run build          # build the website -> apps/mnswpr/dist
+pnpm -F mnswpr run build:preview  # build the app and serve the production preview
 ```
 
-Tests live in `test/` and run under **Vitest** with a jsdom environment (config in `vitest.config.js`). They cover the shared utils and drive the engine through real DOM events (mount `#app`, dispatch mouse events, assert on cell/grid attributes). For anything visual or input-timing related, also verify by running `pnpm dev` and playing.
+### Infra (local CLI only — no web dashboards)
+
+**Every infra operation — provision, deploy hosting, deploy DB, manage env — is doable from the CLI, and every configuration/schema is codified in-repo.** Nothing lives only in a web dashboard. There are two distinct layers, both owned by the app:
+
+**1. App infra *config* — declarative, committed, deployed state.** These files ARE the source of truth; deploying just pushes them up. For `mnswpr`, all under `apps/mnswpr/`:
+
+| File | Codifies |
+| --- | --- |
+| `firebase.json` | Firestore + emulator wiring (rules/indexes paths, emulator ports) |
+| `.firebaserc` | Firebase project aliases (`default`/`prod`/`dev`) |
+| `firestore.rules` | Firestore security rules (server-side access control) |
+| `firestore.indexes.json` | Firestore indexes (none needed — documented inline) |
+| `netlify.toml` | Netlify hosting: build command, publish dir, redirects, headers, build env |
+| `.env.example` | The full env-var contract; real prod values are set as Netlify env vars via CLI, never committed |
+
+**2. App infra *tools* — the CLIs that act on that config.** They are versioned **devDependencies** of the app (not `npx`-on-demand, not global installs), so `pnpm install` pins them and every machine gets the same version. `mnswpr` depends on `firebase-tools` and `netlify-cli`; its scripts call the `firebase`/`netlify` binaries directly (pnpm puts the app's `node_modules/.bin` on `PATH`). A future app using a different stack (Postgres, a different host) declares *its* CLIs as *its* devDependencies and backs the same generic script names — so `pnpm -F <name> run deploy:db` stays uniform.
+
+Each app **owns its infra scripts** in its own `package.json` under generic, tech-agnostic names (`deploy:db`, not `deploy:firestore`) — run them by targeting the app with pnpm's `-F` filter (no root wrapper scripts):
+
+```bash
+pnpm -F mnswpr run db:start      # local DB emulator (mnswpr -> Firestore), standalone
+pnpm -F mnswpr run db:seed       # seed the running local emulator
+pnpm -F mnswpr run db:stop       # kill a stray/orphaned Firestore emulator holding :8080
+pnpm -F mnswpr run deploy:db     # deploy DB rules/indexes (-> firebase deploy --only firestore)
+pnpm -F mnswpr run deploy:site   # build + deploy hosting (-> netlify deploy --prod --dir=dist)
+```
+
+**One-time per app / per machine (all CLI, no dashboard):**
+
+```bash
+pnpm -F mnswpr exec firebase login             # auth the Firebase CLI
+pnpm -F mnswpr exec netlify login              # auth the Netlify CLI
+pnpm -F mnswpr exec netlify link               # bind the app dir to its Netlify site (writes .netlify/, gitignored)
+```
+
+**Managing hosting env vars via CLI** (keeps prod Firebase keys + `VITE_LB_NAMESPACE=mw` out of git while still reproducible):
+
+```bash
+pnpm -F mnswpr exec netlify env:set VITE_LB_NAMESPACE mw   # set one var
+pnpm -F mnswpr exec netlify env:import .env.production      # bulk-import from a local (gitignored) env file
+pnpm -F mnswpr exec netlify env:list                       # inspect what's set
+```
+
+**Non-npm tools get a setup script instead of a devDependency.** The Firestore emulator needs **Java** (it's a JVM program), which isn't an npm package — so `pnpm install` runs a root `postinstall` (`scripts/ensure-java.mjs`) that installs a user-local Temurin JRE 21 into `~/.local` without `sudo` when `java` is missing — idempotent, non-fatal, and auto-skipped on `CI` / `SKIP_JRE_SETUP` / unsupported platforms. Any future infra tool that isn't on npm follows the same pattern (a checked-in setup script), never a manual install step.
+
+Tests are co-located with the package they exercise (`packages/utils/test/`, `packages/mnswpr/test/`) and run under **Vitest** with a jsdom environment (root config in `vitest.config.js`). They cover the shared utils and drive the engine through real DOM events (mount `#app`, dispatch mouse events, assert on cell/grid attributes). For anything visual or input-timing related, also verify by running `pnpm -F mnswpr run dev` and playing.
 
 Node version: `.nvmrc` pins `lts/*`.
 
-## Repository layout (pnpm workspace)
+## Repository layout (Cozy Games monorepo, pnpm workspace)
 
-Workspaces are declared in `pnpm-workspace.yaml` as `lib` and `app`. Note that `utils/` is **not** a workspace package — it's a plain shared folder imported by relative path from both `lib` and `app`.
+This is the **Cozy Games** monorepo. Workspaces are declared in `pnpm-workspace.yaml` as `apps/*`, `packages/*`, and `sites/*`. `utils/` is now a real workspace package (`@cozy-games/utils`), imported by name — no more `../utils` relative paths.
 
-- **`lib/`** — `@ayo-run/mnswpr`, the standalone, framework-free game engine. This is what gets published to npm. `lib/mnswpr.js` is the whole engine; `lib/levels.js` defines the four difficulty presets. Depends only on `utils/`.
+- **`apps/mnswpr/`** — package `mnswpr`, `@cozy-games/mnswpr`'s host, the mnswpr.com website. Consumes the engine and leaderboard via `workspace:*` (`import mnswpr from '@cozy-games/mnswpr/mnswpr.js'`) and wires them together in `apps/mnswpr/main.js`. Owns its Firebase config (`firebase.json`, `firestore.rules`, `.firebaserc`) and app-specific scripts (`apps/mnswpr/scripts/`). A future app (e.g. sudoku) gets its own `apps/<name>/` and its `package.json` `name` is just the app name (`<name>`, unscoped) so it's addressable directly by name (`pnpm -F <name> run <script>`).
-- **`app/`** — the mnswpr.com website. Consumes the library via `workspace:*` (`import mnswpr from '@ayo-run/mnswpr/mnswpr.js'`) and adds the Firebase leaderboard. `app/main.js` wires the engine to the leaderboard through the engine's hooks.
+- **`packages/mnswpr/`** — `@cozy-games/mnswpr`, the standalone, framework-free game engine published to npm. `packages/mnswpr/mnswpr.js` is the whole engine; `levels.js` defines the four difficulty presets. Depends only on `@cozy-games/utils`.
-- **`utils/`** — shared services with no dependencies, re-exported from `utils/index.js`: `StorageService` (localStorage/sessionStorage JSON wrapper), `TimerService` (game clock + `pretty()` time formatting used by both engine and leaderboard), `LoggerService`, `LoadingService`.
+- **`packages/leaderboard/`** — `@cozy-games/leaderboard`, a backend-agnostic, time-windowed leaderboard (adapter-injected storage).
+- **`packages/utils/`** — `@cozy-games/utils`, shared services with no dependencies, re-exported from `index.js`: `StorageService`, `TimerService` (`pretty()` time formatting used by both engine and leaderboard), `LoggerService`, `LoadingService`, and date-bucket helpers.
+- **`sites/`** — docs (Astro Starlight) and UI demos. Placeholders for now.
 
 ## Architecture
 
-**The engine is decoupled from the app via two hooks.** `Minesweeper(appId, version, hooks)` (`lib/mnswpr.js`) is a classic constructor function that imperatively builds a `<table>` grid in the DOM. It knows nothing about Firebase or leaderboards. The app injects behavior through:
+**The engine is decoupled from the app via two hooks.** `Minesweeper(appId, version, hooks)` (`packages/mnswpr/mnswpr.js`) is a classic constructor function that imperatively builds a `<table>` grid in the DOM. It knows nothing about Firebase or leaderboards. The app injects behavior through:
 
 - `hooks.levelChanged(setting)` — fired when the difficulty level changes; the app uses this to re-fetch and render the leaderboard for that level.
 - `hooks.gameDone(game)` — fired when a game ends (win or loss) with a `game` object (`time`, `status`, `level`, `time_stamp`, `isMobile`); the app uses this to submit the score.
@@ -47,9 +100,9 @@ When adding engine features that the website needs to react to, prefer adding a
 
 **Input handling is intricate.** Mouse (left/right/middle, plus simultaneous left+right "chording") and touch (long-press to flag) are handled through a state machine of flags (`isLeft`, `isRight`, `pressed`, `bothPressed`, `skip`, `isBusy`) in `initializeEventHandlers`/`initializeTouchEventHandlers`. `isBusy` debounces input (`MOBILE_BUSY_DELAY`/`PC_BUSY_DELAY`). Tread carefully here — small changes easily break chording or mobile flagging.
 
-**Test mode:** set `TEST_MODE = true` at the top of `lib/mnswpr.js` to render mine positions as visual hints and enable debug logging.
+**Test mode:** set `TEST_MODE = true` at the top of `packages/mnswpr/mnswpr.js` to render mine positions as visual hints and enable debug logging.
 
-## Leaderboard / Firebase (`app/modules/`)
+## Leaderboard / Firebase (`apps/mnswpr/modules/`)
 
 `LeaderBoardService` (`leader-board.js`) reads/writes Firestore (`firebase/firestore/lite`). Structure: top-10 per level in `mw-leaders/{level}/games`, all sessions in `mw-all/{browserId}/games`, and remote runtime `configuration` in `mw-config`. A score is only offered to the leaderboard when it beats the current 10th place *and* matches the server-side `passingStatus`.
 
@@ -60,9 +113,9 @@ The **Firebase config in `leader-board.js` is intentionally public and committed
 ## Conventions
 
 - **Code style is enforced by ESLint Stylistic**, not Prettier: 2-space indent, single quotes, **no semicolons**, no trailing commas, spaces inside `{ braces }` but not `[brackets]`. Run `pnpm lint:fix` before committing. Both `**/*.js` and `**/*.css` are linted (CSS via `@eslint/css`).
-- The engine uses **plain functions and `var`/`let` closures**, not classes; `utils/` and `app/modules/` use ES classes. Match the surrounding style of the file you edit.
+- The engine uses **plain functions and `var`/`let` closures**, not classes; `packages/utils/` and `apps/mnswpr/modules/` use ES classes. Match the surrounding style of the file you edit.
 
 ## Release & git hooks (maintainer workflow)
 
 - **Husky hooks:** `pre-commit` runs `pnpm lint`; `post-commit` auto-pushes to two extra remotes (`git push gh`, `git push sh`). If those remotes aren't configured locally, expect post-commit failures — that's environmental, not a code problem.
-- **Releasing** (`pnpm release`) builds the lib, runs `bumpp` (version bump + tag) in `lib/`, then `scripts/release.js` force-pushes a `release` branch and tags to remotes `gh`/`sh`. Pushing a `v*` tag triggers `.github/workflows/release.yml` (`changelogithub`) to publish GitHub release notes. Only run this when explicitly releasing.
+- **Releasing** (`pnpm release`) builds the lib, runs `bumpp` (version bump + tag) in `packages/mnswpr/`, then `scripts/release.js` force-pushes a `release` branch and tags to remotes `gh`/`sh`. Pushing a `v*` tag triggers `.github/workflows/release.yml` (`changelogithub`) to publish GitHub release notes. Only run this when explicitly releasing.

AYO.md

@@ -1,92 +0,0 @@
-# 🧹 AYO — Leaderboard Migration Checklist
-
-Manual steps to finish the leaderboard rollout. **All code changes are already
-applied** in the working tree — these are the external actions on Firebase and
-Netlify that have to be done by hand.
-
-> One project (`secure-moment-188701`), one difference between environments: the
-> **collection namespace**. Production uses `mw-*`, dev/test uses `mw-test-*`.
-> Full rationale: [`docs/leaderboard-env-migration.md`](docs/leaderboard-env-migration.md).
-
----
-
-## ✅ Step 1 — Deploy Firestore rules + indexes
-
-From the repo root:
-
-```bash
-npx firebase login
-npx firebase deploy --only firestore:rules,firestore:indexes --project prod
-```
-
-- Uses committed [`firestore.rules`](firestore.rules) + [`firestore.indexes.json`](firestore.indexes.json).
-- `prod` → `secure-moment-188701` (via [`.firebaserc`](.firebaserc)).
-- ⚠️ Deploying **replaces** the console rules. The committed rules cover every
-  collection (`mw-*` and `mw-test-*`), so it's safe — but review first.
-- No composite indexes to build — rolling windows (`time_stamp >=`) and all-time
-  (`orderBy score`) use Firestore's automatic single-field indexes.
-
-## ✅ Step 2 — Set Netlify environment variables
-
-In the Netlify site settings, add:
-
-| Variable | Value |
-| --- | --- |
-| `VITE_FIREBASE_API_KEY` … (all 8) | **same as [`app/.env.development`](app/.env.development)** (same project) |
-| `VITE_LB_NAMESPACE` | **`mw`** ← makes production use the `mw-*` collections |
-
-> Local dev already uses `mw-test` via the committed `.env.development` — nothing
-> to do there.
-
-## ✅ Step 3 — (Optional) Seed the test config doc
-
-Create `mw-test-config/configuration` in Firestore with the same `passingStatus`
-and `message` as the prod `mw-config/configuration`.
-
-Skip it and the test board still works — the default qualifier just accepts all
-wins in test.
-
-## ✅ Step 4 — Seed the dev database with sample scores
-
-> ⚠️ **Must run _after_ Step 1.** The seed writes to `mw-test-scores`, which is
-> only allowed once the generalized rules are deployed — otherwise every write
-> returns `permission-denied`. (No indexes to wait on — the windows use
-> automatic single-field indexes.)
-
-Populate the dev boards so they aren't empty while developing:
-
-```bash
-(cd app && node ../scripts/seed-dev-scores.js)
-```
-
-- Uses [`scripts/seed-dev-scores.js`](scripts/seed-dev-scores.js) — ~12 sample
-  scores per level, timestamps spread across today / this week / this month /
-  older so **all four tabs** populate.
-- Dev-only and idempotent-ish (re-running just adds more rows); it never touches
-  the production `mw-*` collections.
-
-> 💡 **Local dev uses the emulator by default — this cloud seed is optional.**
-> `pnpm dev` points at the local **Firestore emulator** (needs a JDK): run
-> `pnpm emulators` + `pnpm seed:emulator` and you're set — no deploy, no cloud.
-> The cloud seed above is only needed for a hosted/preview environment. To opt
-> out of the emulator, set `VITE_FIRESTORE_EMULATOR=` empty in `app/.env.local`.
-> See [`docs/firebase-leaderboards.md`](docs/firebase-leaderboards.md#local-firestore-emulator-default-for-local-dev).
-
-## ✅ Step 5 — Verify
-
-| Environment | How | Expected |
-| --- | --- | --- |
-| **Production** (`mw`) | Win a game on the live site | Score shows; doc in `mw-scores/{level}/games` |
-| **Local dev** (`mw-test`) | `pnpm dev` (after Step 4) | Board shows sample scores; winning adds to `mw-test-scores/{level}/games`; prod `mw-scores` untouched |
-| **Rules** | Read both boards | Reads succeed; a malformed write is rejected |
-
----
-
-## 📌 Still open (not blocking)
-
-- **Nothing is committed yet** — all changes are in the working tree.
-- **`scripts/export-legends.js`** still hard-codes the (dev = prod) Firebase keys
-  from the one-off Legends export. It's identical to `app/.env.development`; can
-  be de-duped to read from the env file on request.
-- **Legends** is already frozen into static HTML ([`app/legends.html`](app/legends.html))
-  — no action needed.

CONTRIBUTING.md

@@ -0,0 +1,122 @@
+# Contributing to Cozy Games
+
+Thanks for your interest in contributing! This guide covers what you need to
+develop, test, and submit changes.
+
+> Working as an AI coding agent? See [AGENTS.md](AGENTS.md) for machine-oriented
+> guidance. This document is for human contributors.
+
+## Prerequisites
+
+- **Node.js** — the version pinned in [`.nvmrc`](.nvmrc) (`lts/*`). With
+  [nvm](https://github.com/nvm-sh/nvm): `nvm use`.
+- **pnpm** — this is a [pnpm](https://pnpm.io) workspace; **pnpm is required**
+  (npm/yarn will not work). The repo pins its pnpm version via the
+  `packageManager` field, so the simplest way to get the right one is Corepack:
+  `corepack enable`.
+- **Java (JDK 11+, 21 recommended)** — only needed to run the local Firestore
+  emulator (used by the mnswpr app's leaderboard in development). `pnpm install`
+  tries to install a user-local Temurin JRE automatically; if that is skipped (CI
+  or an unsupported platform) install a JDK yourself. You can avoid Java entirely
+  with the `dev:no-db` script below.
+
+## Project Structure
+
+- `apps/` - Playable games (each deploys independently)
+- `packages/` - Shared, publishable libraries
+- `sites/` - Docs (Astro Starlight) and UI demos  — placeholders for now
+
+Each app owns its own backend config (e.g. mnswpr's Firestore rules live in
+`apps/mnswpr/`); the shared packages stay backend-agnostic.
+
+## Setup
+
+```bash
+pnpm i        # install all workspace dependencies
+```
+
+## Workspace commands (run from the repo root)
+
+```bash
+pnpm test           # run the whole test suite once (Vitest, jsdom)
+pnpm test:watch     # tests in watch mode
+pnpm lint           # eslint (JS + CSS)
+pnpm lint:fix       # eslint --fix
+pnpm build:lib      # build the publishable engine -> packages/mnswpr/dist
+```
+
+## Running a game locally
+
+Apps aren't run from the root — target one by name with pnpm's `-F` filter. Apps
+are named `<name>` (e.g. `mnswpr`), so every app runs the same way
+(`pnpm -F <name> run <script>`):
+
+```bash
+pnpm -F mnswpr run dev          # Vite dev server + Firestore emulator (auto-seeded) — needs Java
+pnpm -F mnswpr run dev:no-db    # Vite only, no emulator (UI work, or no Java)
+pnpm -F mnswpr run build        # build the app     -> apps/mnswpr/dist
+pnpm -F mnswpr run preview      # preview the production build
+```
+
+## Tests
+
+Tests run under **Vitest** with a **jsdom** environment and live next to the code
+they exercise (`packages/*/test/`). They drive real behavior — e.g. mounting the
+game and dispatching DOM events — not just isolated unit calls. Run `pnpm test`
+(or `pnpm test:watch`) before opening a PR, and add tests for new behavior.
+
+## Code style
+
+Style is enforced by **ESLint (Stylistic)**, not Prettier:
+
+- 2-space indent, single quotes, **no semicolons**, no trailing commas
+- spaces inside `{ braces }` but not `[brackets]`
+- both `**/*.js` and `**/*.css` are linted
+
+Run `pnpm lint:fix` before committing. The codebase is **plain JavaScript with
+JSDoc + `// @ts-check`** — no TypeScript. Match the style and patterns of the file
+you're editing (the game engine uses plain functions and closures; `packages/utils`
+and the app modules use ES classes).
+
+A **pre-commit hook** runs the linter and a secret scan automatically — commits
+fail if either does. Keep credentials and any `.env.production` out of commits.
+
+## Infra & local backend (optional)
+
+Only relevant if you're working on backend-touching features. Every app **owns its
+own backend config** (declarative, committed in-repo) and its tooling (CLIs as
+devDependencies) — no web dashboards. For mnswpr (Firestore + Netlify), the local
+DB emulator is all a contributor needs:
+
+```bash
+pnpm -F mnswpr run db:start   # start the local Firestore emulator (standalone) — needs Java
+pnpm -F mnswpr run db:seed    # seed the running emulator with sample data
+pnpm -F mnswpr run db:stop    # stop a stray emulator holding :8080
+```
+
+Deploy scripts (`deploy:db`, `deploy:site`) also exist but require project
+credentials, so they're for maintainers. See
+[apps/mnswpr/README.md](apps/mnswpr/README.md) and that app's `docs/` for the full
+backend reference.
+
+## Project structure & decisions
+
+The repo layout is in the [README](README.md#layout). Significant architecture
+choices are recorded in [`docs/decisions/`](docs/decisions/) — worth a read before
+a large change. Shared packages stay backend-agnostic; each app owns its own
+backend config.
+
+## Submitting changes
+
+1. Create a branch off `main`.
+2. Make a focused change.
+3. Run `pnpm lint` and `pnpm test` — both must pass.
+4. Write clear, conventional commit messages (`feat:`, `fix:`, `chore:`, …).
+5. Open a pull request describing **what** changed and **why**; link any related issue.
+
+For anything large, open an issue to discuss the approach first.
+
+## License
+
+By contributing, you agree that your contributions are licensed under the
+project's [BSD-2-Clause license](LICENSE).

README.md

@@ -1,123 +1,45 @@
-> [!IMPORTANT]
+# Cozy Games
-> **mnswpr has a new home.** Development now happens in the **Cozy Games** monorepo:
-> **[git.ayo.run/ayo/cozy-games](https://git.ayo.run/ayo/cozy-games)**.
 
-# Play Minesweeper Online for Free
+A growing collection of small browser games and the shared, reusable packages that power them.
-[![Netlify Status](https://api.netlify.com/api/v1/badges/172478bd-afc5-4e47-95ba-d9ab814248fb/deploy-status)](https://app.netlify.com/sites/mnswpr/deploys)
 
-Play it here: [mnswpr.com](https://mnswpr.com). This is the classic game **Minesweeper** built with vanilla web technologies (i.e., no framework dependency).
+> [!Note]
+> This repo was originally for [mnswpr](https://mnswpr.com) (see its [README](apps/mnswpr/README.md)) which has been evolved in *2026* to understand AI-assisted development. The purpose of mnswpr has always included understanding the web development landscape and this has changed significantly with the rise of LLMs.
 
-![mnswpr gameplay](https://git.ayo.run/ayo/mnswpr/raw/branch/main/screenshot.png)
+# Roadmap
 
-## How to Play
+- **Public APIs** — game-agnostic modules (core, move-log, replay, leaderboard, rating) built inside the first game.
+- **Second Game** — validate those APIs by adding a second game through the adapter alone.
+- **Reusable Packages** — extract proven modules into standalone, versioned packages.
+- **Adapters** — freeze the adapter contract for third-party games to build against.
 
-The goal is to reveal every safe cell without detonating a mine. Your **first click is always safe**.
+## Packages
 
-- **Left click** — reveal a cell
+| Package              | Develop        | Publish | Document |
-- **Right click** — flag / unflag a suspected mine
+| -------------------- | -------------- | ------- | -------- |
-- **Left + right click together** (chording) — reveal the neighbors of a satisfied number
+| `mnswpr` (game core) | ✅ Built       |         |          |
-- **Touch** — tap to reveal, long-press to flag
+| leaderboard          | ✅ Built       |         |          |
+| move-log             | ✅ Built       |         |          |
+| replay engine        | ✅ Built       |         |          |
+| rating math          | 🚧 Development |         |          |
+| `sudoku` (game core) | 🔮 Planned     |         |          |
 
-
+> Note: `@ayo-run/mnswpr` on npm predates this project and will be deprecated in favor of `cozy-games/mnswpr`.
-## Ways to Use
-
-The web is a wonderful, free, and open platform to create and distribute value. You can use **mnswpr** in different ways:
-
-- as a deployed [web app](https://mnswpr.com)
-- as a [library](https://npmx.dev/package/@ayo-run/mnswpr) with `npm i @ayo-run/mnswpr`
-- as a `web component` (coming soon).
-
-Using it as a library takes only a few lines — mount it onto any element by `id`:
-
-```js
-import '@ayo-run/mnswpr/mnswpr.css'
-import mnswpr from '@ayo-run/mnswpr'
-
-const game = new mnswpr('app')
-game.initialize()
-```
-
-## Tooling
-The project has gone through years of existence. It started from 2019 when tooling was massively different. I have [modernized it](https://elk.zone/social.ayco.io/@ayo/116333804543330938) since and have witnessed how much easier and faster it is to build now - even without web frameworks or LLMs!
-
-As of now the tooling I use are:
-- [Vite](https://vite.dev/) for bundling and development server
-- [Eslint](https://eslint.org) for JS linting & [CSS linting](https://eslint.org/blog/2025/02/eslint-css-support/)
-- [ESLint Stylistic](https://eslint.style) for JS formatting
-- [Husky](https://typicode.github.io/husky/) for git hooks
-- [PNPM](https://pnpm.io/installation) for dependency & workspace management
-- and a bunch of automation using scripts and Continuous Integration actions
-
-Because a big part of this project's purpose is to track how the software development industry evolves — and because it has come a long way in modernizing along the way — I now also use it as a **playground for coding agents**. It's a small, framework-free, well-scoped codebase, which makes it a great sandbox to see how AI agents read, reason about, and change real code. To help them get their bearings quickly, the repo ships an [`AGENTS.md`](./AGENTS.md) describing the architecture and conventions.
-
-## Development
-
-Technology Stack: HTML, JS, and CSS; [Google Firebase](https://firebase.google.com) for leader board store; [Netlify](https://netlify.com) for hosting
-
-To start development, you need [`node`](https://nodejs.org/en/download). I highly recommend [`pnpm`](https://pnpm.io/installation) to be used as well. Once you know you have this, you can do the following:
-1. Install dependencies: `pnpm i`
-2. Start the dev server: `pnpm run dev`
-
-The rest of the everyday commands:
-
-```bash
-pnpm test        # run the Vitest suite
-pnpm lint        # ESLint (JS + CSS)
-pnpm lint:fix    # ESLint with autofix
-pnpm build       # build the website
-pnpm build:lib   # build the publishable library
-```
-
-### Leaderboard (local Firestore emulator)
-
-The leader board is backed by [Google Firestore](https://firebase.google.com). For local development the app talks to the **Firestore emulator** by default — fully local, no cloud, no deploy. The flag `VITE_FIRESTORE_EMULATOR=1` is already set in `app/.env.development`.
-
-You need a **JDK 21+** installed (the emulator runs on Java; `firebase-tools` itself is fetched on demand via `npx`). Then, in two terminals:
-
-```bash
-pnpm emulators      # terminal 1 — start the Firestore emulator on :8080 (+ UI)
-pnpm seed:emulator  # terminal 2, once — fill it with sample scores
-pnpm dev            # terminal 2 — run the app against the emulator
-```
-
-If the emulator isn't running, the board simply shows *"unavailable"* (a refused connection). To skip the emulator — for quick UI-only work, or if you don't have a JDK — set `VITE_FIRESTORE_EMULATOR=` (empty) in a local, gitignored `app/.env.local`; the app then uses the cloud `mw-test` namespace instead.
-
-See [`docs/firebase-leaderboards.md`](./docs/firebase-leaderboards.md) for the full data model, security rules, environments, and deployment.
 
 ## Contributing
 
-Contributions are welcome! See [`AGENTS.md`](./AGENTS.md) for the architecture, conventions, and release workflow before opening a pull request.
+Setup, running games locally, testing, code style, and local infra all live in
-
+**[CONTRIBUTING.md](CONTRIBUTING.md)**. In short — this is a
-## You just want to play?
+[pnpm](https://pnpm.io) workspace:
-
-*👉 The live site is here: [mnswpr.com](https://mnswpr.com)*
-
-## Background
-One day, while working in my home office, I heard loud and fast mouse clicks coming from our bedroom. It's my wife, playing her favorite game (Minesweeper) on a crappy website full of advertisements.
-
-I can't allow this, it's a security issue. 🤣
-
-But it is also an opportunity.
-
-I wanted to give her the same game, with a similar leader board she can dominate. And this is also a chance for me to dig deeper into vanilla JS.
-
-Can I make a page with complex interactions (more on this later) without any library dependency?
-
-## What I have learned:
-1. JS is awesome ✨
-1. We don't always *need* JS frameworks (or TS) ✨
-1. Even subtle UI changes *can improve* user gameplay experience ✨
-1. There's more ways to break your app than you are initially aware of ✨
-1. Competition motivates users to use your app more ✨
-1. Hash in bundled filenames helps avoid issues with browser caching (when shipping versions fast) ✨
 
+```bash
+pnpm i                     # install
+pnpm test                  # run the test suite
+pnpm -F mnswpr run dev     # run the Minesweeper app locally
+```
 
+See [apps/mnswpr/README.md](apps/mnswpr/README.md) for the game itself, and each
+package's README for library usage.
 
 ## License
 
-[BSD-2-Clause](./LICENSE)
+BSD-2-Clause © Ayo Ayco
-
----
-
-_Just keep building._<br>
-_A project by [Ayo](https://ayo.ayco.io)_

app/package.json

@@ -1,19 +0,0 @@
-{
-  "name": "app",
-  "version": "0.0.1",
-  "description": "the mnswpr.com web app",
-  "private": true,
-  "main": "main.js",
-  "scripts": {
-    "build": "vite build",
-    "preview": "vite preview",
-    "build:preview": "npm run build && npm run preview"
-  },
-  "devDependencies": {
-    "@ayo-run/mnswpr": "workspace:*",
-    "@cozy-games/leaderboard": "workspace:*",
-    "firebase": "^12.11.0",
-    "web-component-base": "^4.1.2"
-  },
-  "author": "Ayo Ayco"
-}

apps/mnswpr/README.md

@@ -3,28 +3,7 @@
 
 Play it here: [mnswpr.com](https://mnswpr.com). This is the classic game **Minesweeper** built with vanilla web technologies (i.e., no framework dependency).
 
-<!-- TODO: replace with the actual screenshot/GIF once supplied (confirm final path/filename) -->
+![mnswpr gameplay](https://git.ayo.run/ayo/mnswpr/raw/branch/main/screenshot.png)
-![mnswpr gameplay](app/public/screenshot.png)
-
-Technology Stack: HTML, JS, and CSS; [Google Firebase](https://firebase.google.com) for leader board store; [Netlify](https://netlify.com) for hosting
-
-## Usage
-
-The web is a wonderful, free, and open platform to create and distribute value. You can use **mnswpr** in different ways:
-
-- as a deployed [web app](https://mnswpr.com)
-- as a [library](https://npmx.dev/package/@ayo-run/mnswpr) with `npm i @ayo-run/mnswpr`
-- as a `web component` (coming soon).
-
-Using it as a library takes only a few lines — mount it onto any element by `id`:
-
-```js
-import '@ayo-run/mnswpr/mnswpr.css'
-import mnswpr from '@ayo-run/mnswpr'
-
-const game = new mnswpr('app')
-game.initialize()
-```
 
 ## How to Play
 
@@ -35,6 +14,25 @@ The goal is to reveal every safe cell without detonating a mine. Your **first cl
 - **Left + right click together** (chording) — reveal the neighbors of a satisfied number
 - **Touch** — tap to reveal, long-press to flag
 
+
+## Ways to Use
+
+The web is a wonderful, free, and open platform to create and distribute value. You can use **mnswpr** in different ways:
+
+- as a deployed [web app](https://mnswpr.com)
+- as a [library](https://npmx.dev/package/@cozy-games/mnswpr) with `npm i @cozy-games/mnswpr`
+- as a `web component` (coming soon).
+
+Using it as a library takes only a few lines — mount it onto any element by `id`:
+
+```js
+import '@cozy-games/mnswpr/mnswpr.css'
+import mnswpr from '@cozy-games/mnswpr'
+
+const game = new mnswpr('app')
+game.initialize()
+```
+
 ## Tooling
 The project has gone through years of existence. It started from 2019 when tooling was massively different. I have [modernized it](https://elk.zone/social.ayco.io/@ayo/116333804543330938) since and have witnessed how much easier and faster it is to build now - even without web frameworks or LLMs!
 
@@ -49,20 +47,73 @@ As of now the tooling I use are:
 Because a big part of this project's purpose is to track how the software development industry evolves — and because it has come a long way in modernizing along the way — I now also use it as a **playground for coding agents**. It's a small, framework-free, well-scoped codebase, which makes it a great sandbox to see how AI agents read, reason about, and change real code. To help them get their bearings quickly, the repo ships an [`AGENTS.md`](./AGENTS.md) describing the architecture and conventions.
 
 ## Development
+
+Technology Stack: HTML, JS, and CSS; [Google Firebase](https://firebase.google.com) for leader board store; [Netlify](https://netlify.com) for hosting
+
 To start development, you need [`node`](https://nodejs.org/en/download). I highly recommend [`pnpm`](https://pnpm.io/installation) to be used as well. Once you know you have this, you can do the following:
 1. Install dependencies: `pnpm i`
-2. Start the dev server: `pnpm run dev`
+2. Start the dev server: `pnpm -F mnswpr run dev`
 
 The rest of the everyday commands:
 
 ```bash
-pnpm test        # run the Vitest suite
+pnpm test                          # run the Vitest suite (workspace-wide)
 pnpm lint                          # ESLint (JS + CSS)
 pnpm lint:fix                      # ESLint with autofix
-pnpm build       # build the website
+pnpm -F mnswpr run build      # build the website
 pnpm build:lib                     # build the publishable library
 ```
 
+### Leaderboard (local Firestore emulator)
+
+The leader board is backed by [Google Firestore](https://firebase.google.com). For local development the app talks to the **Firestore emulator** by default — fully local, no cloud, no deploy. The flag `VITE_FIRESTORE_EMULATOR=1` is already set in `app/.env.development`.
+
+`dev` is the whole loop in one command — it wraps Vite in `firebase emulators:exec`, so the Firestore emulator (on :8080, + UI) comes up, gets **seeded with sample scores automatically**, and the app dev server starts against it; everything shuts down when you stop it. (Each `dev` starts a fresh in-memory emulator, so the auto-seed writes exactly one clean set every time — no accumulation.) `firebase-tools` is a pinned **devDependency** of this app (installed by `pnpm install`, invoked as the `firebase` binary), so the only extra prerequisite is **Java** — the Firestore emulator is a Java program (`java -jar cloud-firestore-emulator-*.jar`), and firebase-tools does not bundle a JRE.
+
+**Usually automatic.** `pnpm install` runs a root `postinstall` ([`scripts/ensure-java.mjs`](../../scripts/ensure-java.mjs)) that installs a user-local Temurin JRE 21 into `~/.local` (no `sudo`) when `java` isn't already on your PATH. It's idempotent and never fails the install, and it skips when `CI` or `SKIP_JRE_SETUP=1` is set, or on unsupported platforms.
+
+If that skipped and you need Java (or prefer a system-wide install), do it manually — **install a JRE (Java 11+; 21 recommended):**
+
+```bash
+# Debian / Ubuntu / Pop!_OS
+sudo apt update && sudo apt install -y openjdk-21-jre-headless
+
+# Fedora
+sudo dnf install -y java-21-openjdk-headless
+
+# macOS (Homebrew)
+brew install openjdk@21
+
+java -version   # verify: should print "openjdk 21.x" (or 11+)
+```
+
+No `sudo`? Install a JRE into your home directory instead (no root needed):
+
+```bash
+curl -fsSL -o /tmp/jre21.tgz "https://api.adoptium.net/v3/binary/latest/21/ga/linux/x64/jre/hotspot/normal/eclipse"
+mkdir -p ~/.local/lib && tar xzf /tmp/jre21.tgz -C ~/.local/lib
+ln -sf ~/.local/lib/jdk-21*-jre/bin/java ~/.local/bin/java   # ~/.local/bin is already on PATH
+java -version
+```
+
+Without Java, `dev` and `db:start` fail with `Could not spawn 'java -version'`. Install it to a permanent location — a JRE unpacked under `/tmp` disappears when the OS cleans temp files. Then just:
+
+```bash
+pnpm -F mnswpr run dev       # emulator (:8080 + UI) + auto-seed + app dev server — one command
+```
+
+That's the everyday loop. The other DB scripts are for when you want to run pieces separately:
+
+```bash
+pnpm -F mnswpr run db:start   # emulator only (stays up across app restarts); pair with dev:no-db
+pnpm -F mnswpr run db:seed    # seed a separately-running emulator (what dev does for you)
+pnpm -F mnswpr run db:stop    # kill a stray/orphaned emulator holding :8080
+```
+
+To skip the emulator entirely — for quick UI-only work, or if you don't have a JDK — run `pnpm -F mnswpr run dev:no-db` (plain Vite) and set `VITE_FIRESTORE_EMULATOR=` (empty) in a local, gitignored `app/.env.local`; the app then uses the cloud `mw-test` namespace instead.
+
+See [`docs/firebase-leaderboards.md`](./docs/firebase-leaderboards.md) for the full data model, security rules, environments, and deployment.
+
 ## Contributing
 
 Contributions are welcome! See [`AGENTS.md`](./AGENTS.md) for the architecture, conventions, and release workflow before opening a pull request.

apps/mnswpr/docs/firebase-leaderboards.md

@@ -98,23 +98,26 @@ Dev config lives in the committed [`app/.env.development`](../app/.env.developme
 
 ### One-time CLI setup
 
-The Firebase project already exists — no need to create it.
+`firebase-tools` is a pinned devDependency of this app (installed by `pnpm install`),
+so run it as the `firebase` binary via pnpm — no global install, no `npx`. The
+Firebase project already exists — no need to create it.
 
 ```bash
-npx firebase login
+pnpm -F mnswpr exec firebase login
 ```
 
 ### Deploy rules + indexes
 
-Deploys go to **production** by default. Target a project explicitly with
+The `deploy:db` script (`pnpm -F mnswpr run deploy:db`) deploys everything under
-`--project`:
+`firestore` to the **default** project. To target a specific project or a subset,
+call the CLI directly:
 
 ```bash
 # production (default alias 'prod')
-npx firebase deploy --only firestore:rules,firestore:indexes --project prod
+pnpm -F mnswpr exec firebase deploy --only firestore:rules,firestore:indexes --project prod
 
 # development database
-npx firebase deploy --only firestore:rules,firestore:indexes --project dev
+pnpm -F mnswpr exec firebase deploy --only firestore:rules,firestore:indexes --project dev
 ```
 
 > ⚠️ Deploying **replaces** whatever rules currently live in the Console. The
@@ -133,16 +136,17 @@ locally (so you validate them before deploying). The flag
 `VITE_FIRESTORE_EMULATOR=1` is set in [`app/.env.development`](../app/.env.development).
 
 > Prerequisite: the Firestore emulator is a Java process, so you need a JDK
-> (11+) installed. `firebase-tools` is fetched on demand via `npx`.
+> (11+) installed. `firebase-tools` is a pinned devDependency of this app
+> (installed by `pnpm install`, run as the `firebase` binary).
 
 Everyday dev loop:
 
 ```bash
-pnpm emulators      # terminal 1: Firestore emulator (+ Emulator UI) on :8080
+pnpm -F mnswpr run dev   # emulator (+ UI) on :8080, auto-seeded with sample scores, + app dev server
-pnpm seed:emulator  # terminal 2, once: fill it with sample scores
-pnpm dev            # terminal 2: app runs against the local emulator
 ```
 
+`dev` seeds the fresh emulator for you (via `emulators:exec "node scripts/seed-dev-scores.js; vite"`). Use the standalone `db:start` / `db:seed` scripts only when running the emulator separately from the app.
+
 Wiring: `app/main.js` passes `{ emulator: { host, port } }` to `FirebaseAdapter`,
 which calls `connectFirestoreEmulator`. If the emulator isn't running the board
 just shows "unavailable" (a refused connection) — start it, or opt out.

apps/mnswpr/docs/leaderboard-env-migration.md

@@ -139,8 +139,8 @@ Both aliases target the one project we actually have:
 
 ### 7. Deploy & verify
 
-1. `npx firebase deploy --only firestore:rules,firestore:indexes --project prod`
+1. `pnpm -F mnswpr exec firebase deploy --only firestore:rules,firestore:indexes --project prod`
-2. Set the Netlify env vars (`VITE_LB_NAMESPACE=mw` + `VITE_FIREBASE_*`).
+2. Set the Netlify env vars via CLI: `pnpm -F mnswpr exec netlify env:import .env.production` (or `netlify env:set VITE_LB_NAMESPACE mw` + each `VITE_FIREBASE_*`).
 3. `pnpm dev`, win a game → confirm the write lands in **`mw-test-scores`**, and
    the prod `mw-scores` is untouched (Firestore console).
 4. Confirm reads on both `mw-scores` and `mw-test-scores` succeed under the new

apps/mnswpr/firestore.rules

@@ -4,13 +4,10 @@ rules_version = '2'
 // rules are the enforced schema: public reads for the boards, validated
 // create-only writes for scores, no client writes to server config.
 //
-// SECURITY MODEL: the Firebase web config is public (it ships to every browser),
+// The Firebase web config that ships in the client is public by design (it is
-// so these rules — not secrecy of the config or the codebase — are what protect
+// not a secret); these rules — not secrecy — are what govern access. No
-// the data. No collection allows a client to UPDATE or DELETE existing docs, so
+// collection allows a client to update or delete existing docs. Keep any
-// no client (with or without the source) can wipe the production boards. The
+// admin/service-account credentials out of the repo and locked down in GCP.
-// powerful vectors (Admin SDK / service-account keys, and IAM console access)
-// bypass rules entirely — keep those out of the repo and locked down in GCP.
-// See docs/firebase-leaderboards.md ("Protecting production data").
 //
 // Rules match by namespace SUFFIX (regex) rather than a literal prefix, so the
 // same set covers production (`mw-*`) and test (`mw-test-*`) collections in the
@@ -19,7 +16,7 @@ rules_version = '2'
 // block is guarded by a regex on the captured collection name.
 //
 // Deploy with (see docs/firebase-leaderboards.md):
-//   npx firebase deploy --only firestore:rules --project prod
+//   pnpm -F mnswpr exec firebase deploy --only firestore:rules --project prod
 service cloud.firestore {
   match /databases/{database}/documents {
 
@@ -36,13 +33,15 @@ service cloud.firestore {
       allow write: if false;
     }
 
-    // Per-browser personal archive. Write-only from the client (the app never
+    // Per-browser personal archive. Not readable by clients, append/merge only,
-    // reads it back), append/merge only, and NEVER deletable. This is the only
+    // and never deletable. The doc is a map of gameId -> game object (one doc
-    // client-writable collection, so denying delete/read here removes the last
+    // per day, merged as games finish); the entry-count cap keeps a single doc
-    // way a client could destroy or harvest data.
+    // bounded (Firestore already limits any doc to 1 MiB). 500 is far above any
+    // real day of play.
     match /{all}/{browserId}/games/{session} {
       allow read:           if false;
-      allow create, update: if all.matches('mw(-[a-z]+)?-all');
+      allow create, update: if all.matches('mw(-[a-z]+)?-all')
+                            && request.resource.data.size() <= 500;
       allow delete:         if false;
     }
 

apps/mnswpr/index.html

@@ -10,7 +10,6 @@
 
     <link rel="shortcut icon" type="image/png" href="/favicon.ico" />
     <link rel="stylesheet" href="./main.css" />
-    <link rel="stylesheet" href="../utils/loading/loading.css" />
     <style>
         :host, :root{
             --mnswpr-transition: 10s ease-in-out;

apps/mnswpr/main.js

@@ -1,6 +1,7 @@
-import mnswpr from '@ayo-run/mnswpr/mnswpr.js'
+import mnswpr from '@cozy-games/mnswpr/mnswpr.js'
-import '@ayo-run/mnswpr/mnswpr.css'
+import '@cozy-games/mnswpr/mnswpr.css'
-import * as pkg from '@ayo-run/mnswpr/package.json'
+import '@cozy-games/utils/loading/loading.css'
+import * as pkg from '@cozy-games/mnswpr/package.json'
 import { configureLeaderboard } from '@cozy-games/leaderboard/leaderboard-element.js'
 import { FirebaseAdapter } from '@cozy-games/leaderboard/adapters/firebase.js'
 import { NicknameService } from './modules/nickname/nickname.js'

apps/mnswpr/modules/nickname/nickname.js

@@ -1,4 +1,4 @@
-import { StorageService } from '../../../utils/index.js'
+import { StorageService } from '@cozy-games/utils'
 
 const NICK_KEY = 'nickname'
 const MAX_LENGTH = 24

apps/mnswpr/netlify.toml

@@ -0,0 +1,36 @@
+# Netlify hosting config for mnswpr.com — the app-level, declarative hosting
+# state, codified here so hosting is reproducible from the repo and deployed via
+# CLI (`pnpm -F mnswpr run deploy:site`), never the web dashboard. This file is
+# app infra *config*; the CLI that reads it (`netlify-cli`) is app infra *tooling*
+# and lives in this app's devDependencies. See AGENTS.md "Infra".
+
+# The `deploy:site` script pre-builds locally and uploads `dist` via the CLI, so
+# this [build] block is only exercised when Netlify builds the site from git
+# (dashboard "base directory" = apps/mnswpr). It is a pnpm workspace, so
+# `pnpm install` from here installs the whole monorepo before building.
+[build]
+  command = "pnpm install --frozen-lockfile && pnpm run build"
+  publish = "dist"
+
+[build.environment]
+  NODE_VERSION = "20"
+  # Production leaderboard namespace (dev/test uses `mw-test`). Applies to
+  # git-triggered builds; local CLI builds read app/.env.production instead.
+  # Firebase VITE_* keys are public but are set as Netlify env vars (via
+  # `netlify env:set` / `netlify env:import`, not the dashboard) to keep prod
+  # values out of git — see apps/mnswpr/.env.example.
+  VITE_LB_NAMESPACE = "mw"
+
+# Pretty URL for the frozen Legends page (built as /legends.html).
+[[redirects]]
+  from = "/legends"
+  to = "/legends.html"
+  status = 200
+
+# Baseline security headers applied to every response.
+[[headers]]
+  for = "/*"
+  [headers.values]
+    X-Frame-Options = "SAMEORIGIN"
+    X-Content-Type-Options = "nosniff"
+    Referrer-Policy = "strict-origin-when-cross-origin"

apps/mnswpr/package.json

@@ -0,0 +1,30 @@
+{
+  "name": "mnswpr",
+  "version": "0.0.1",
+  "description": "the mnswpr.com web app",
+  "private": true,
+  "type": "module",
+  "main": "main.js",
+  "scripts": {
+    "dev": "firebase emulators:exec --only firestore --ui \"node scripts/seed-dev-scores.js; vite\"",
+    "dev:no-db": "vite",
+    "build": "vite build",
+    "preview": "vite preview",
+    "build:preview": "npm run build && npm run preview",
+    "deploy:db": "firebase deploy --only firestore",
+    "deploy:site": "npm run build && netlify deploy --prod --dir=dist",
+    "db:start": "firebase emulators:start --only firestore",
+    "db:seed": "FIRESTORE_EMULATOR_HOST=127.0.0.1:8080 node scripts/seed-dev-scores.js",
+    "db:stop": "pkill -f '[c]loud-firestore-emulator'; pkill -f '[f]irebase.* emulators:'; true"
+  },
+  "devDependencies": {
+    "@cozy-games/mnswpr": "workspace:*",
+    "@cozy-games/leaderboard": "workspace:*",
+    "@cozy-games/utils": "workspace:*",
+    "firebase": "^12.11.0",
+    "firebase-tools": "^15.22.4",
+    "netlify-cli": "^26.1.0",
+    "web-component-base": "^5.0.0"
+  },
+  "author": "Ayo Ayco"
+}

apps/mnswpr/scripts/export-legends.js

@@ -1,12 +1,12 @@
 /**
  * One-time generator: snapshot the all-time leaders from the legacy
- * `mw-leaders/{level}/games` collection and write them into app/legends.html as
+ * `mw-leaders/{level}/games` collection and write them into legends.html as
  * a FULLY-RENDERED, static page — no runtime JS, no Firebase at page load.
  *
  * The data never changes, so the page is a frozen artifact. Re-run only if you
  * ever need to regenerate it. Because `firebase` is an app-workspace dependency,
  * run it so Node can resolve it, e.g. from the app directory:
- *   (cd app && node ../scripts/export-legends.js)
+ *   (cd apps/mnswpr && node scripts/export-legends.js)
  */
 import { writeFileSync } from 'node:fs'
 import { resolve, dirname } from 'node:path'
@@ -17,9 +17,9 @@ import {
   getFirestore, getDocs, collection, query, orderBy, limit
 } from 'firebase/firestore/lite'
 
-import { levels } from '../lib/levels.js'
+import { levels } from '@cozy-games/mnswpr/levels.js'
 
-// Mirror of TimerService.pretty() (utils/timer/timer.js) — inlined so this
+// Mirror of TimerService.pretty() (@cozy-games/utils timer) — inlined so this
 // generator has no cross-module import chain to resolve under raw Node.
 const clean = (str, separator) => (str === '00' ? '' : `${str}${separator}`)
 const pretty = duration => {
@@ -131,6 +131,6 @@ ${sections.join('\n')}
 `
 
 const __dirname = dirname(fileURLToPath(import.meta.url))
-const out = resolve(__dirname, '../app/legends.html')
+const out = resolve(__dirname, '../legends.html')
 writeFileSync(out, html)
 console.log(`\nWrote ${out}`)

apps/mnswpr/scripts/seed-dev-scores.js

@@ -13,7 +13,7 @@
  *    firestore.rules to be deployed first (they permit writes to
  *    `mw-test-scores`), else every write returns permission-denied:
  *      npx firebase deploy --only firestore:rules --project dev
- *      (cd app && node ../scripts/seed-dev-scores.js)
+ *      (cd apps/mnswpr && node scripts/seed-dev-scores.js)
  *
  * `firebase` is an app-workspace dependency, so run it from the app directory so
  * Node can resolve it. Optional namespace override: LB_NAMESPACE=mw-test.
@@ -21,7 +21,7 @@
 import { initializeApp } from 'firebase/app'
 import { getFirestore, connectFirestoreEmulator, doc, collection, setDoc } from 'firebase/firestore/lite'
 
-import { buckets } from '../utils/date-bucket/date-bucket.js'
+import { buckets } from '@cozy-games/utils/date-bucket/date-bucket.js'
 
 const firebaseConfig = {
   apiKey: 'AIzaSyCTi_5Sm5dHFNf0d_Gn0MNWmlGheFBf6MQ',

docs/decisions/0001-package-boundary.md

@@ -0,0 +1,30 @@
+# 0001. Backend-agnostic package boundary
+
+**Status:** Accepted · **Repo:** cozy-games · **Date:** 2026-07
+
+## Context
+cozy-games is a collection of reusable game modules (`@cozy-games/mnswpr`, the
+leaderboard package, future extractions). Applications built on these packages
+differ in how they store data, authenticate users, and enforce rules.
+
+## Decision
+Packages in this repo are **backend-agnostic and permission-agnostic**: they
+expose capability, never storage or authorization. Any backend — database, auth,
+server-side logic — is supplied by the consuming application through injected
+adapters and hooks (see 0002). Package code contains no storage-, deployment-, or
+authorization-specific logic.
+
+## Rationale (technical)
+- Permission-agnostic packages are correct library design: authorization and
+  storage belong to each deployment (e.g. via security rules and server-side
+  contexts), not to library code.
+- Backend-agnostic packages are more adoptable, testable, and contributable; any
+  app or backend can consume them.
+- Standalone packages are more reusable and testable than a monolithic app.
+
+## Consequences
+- Public API changes in these packages are semver events for downstream consumers.
+- Contributions must not introduce coupling to any specific backend or deployment.
+- These decision records cover package and architecture decisions only; storage,
+  deployment, and operations choices belong to each consuming application, not to
+  this repo.

docs/decisions/0002-game-adapter-pattern.md

@@ -0,0 +1,34 @@
+# 0002. Game-agnostic cores behind a game-adapter interface
+
+**Status:** Accepted · **Repo:** cozy-games · **Date:** 2026-07
+
+## Context
+Multiple games (Minesweeper today, Sudoku planned) share generic infrastructure:
+move logging, replay, timing, and leaderboards. Building this per-game duplicates
+logic; abstracting prematurely risks wrong boundaries.
+
+## Decision
+Core modules are written **game-agnostic from day one**; each game supplies an
+**adapter**. Package extraction and npm publishing are deferred until a second
+game consumes the seam ("create seams, not packages").
+
+### The adapter contract (v0, will be frozen after the second game ships)
+A game adapter supplies:
+
+1. **Event vocabulary** — a typed set of move events (Minesweeper: `reveal | flag | unflag | chord`). Core code handles only the generic envelope `MoveEvent<T>`: `{ seq, clientTs, type: T, payload }` wrapped in a log carrying `schema_version`.
+2. **Progress reducer** — `progress(events) → percent` for progress display.
+3. **State reducer** — `apply(state, event) → state` for full replay and validation.
+4. **Terminal predicate** — `isTerminal(state) → win | loss | null`; generic timing code measures first event → terminal event.
+5. **Board payload type** — serialized layout (e.g. grid + mine positions) stored as typed JSON under a `game_type` discriminator.
+6. **Headless core** — pure functions (`generateBoard`, reducers, predicates) runnable in Node with no DOM dependency; presentation is a separate layer.
+7. **Board injection & resume** — constructors accepting an externally supplied board and a mid-game state snapshot.
+
+### Rules
+- Core/engine modules import no game-specific types.
+- The event vocabulary and log schema_version live in the game's package; recorded logs are replayable forever (schema changes are versioned, never breaking).
+- Generic storage columns (id, player, outcome, timestamps, game_type) never require migration to add a game; new games add a payload type and adapter only.
+
+## Consequences
+- Adding a game = writing one adapter; infrastructure is untouched.
+- The replay engine and the log envelope become extractable packages once validated by the second adapter.
+- The adapter interface is frozen and versioned after the second game ships; breaking changes thereafter require a new decision record.

docs/decisions/0003-stored-boards-not-seeds.md

@@ -0,0 +1,23 @@
+# 0003. Stored board layouts, not reproducible seeds
+
+**Status:** Accepted · **Repo:** cozy-games · **Date:** 2026-07
+
+## Context
+Replay and shared-board features require two plays of the same board. Two options:
+(a) seeded PRNG generation, where a seed reproduces the board; (b) serialize and
+store the full board layout at game start, referenced by an id.
+
+## Decision
+Store the full layout (b). Boards are serialized as the game's payload (per
+0002 §5) and referenced by an unguessable `game_id`.
+
+## Rationale
+- **No generator lock-in:** seeded reproduction breaks if the generation algorithm ever changes (bugfix, difficulty tuning, library swap). Stored layouts are immune to generator-version drift — old games replay forever.
+- **No refactor required:** existing generators keep working; serialization is additive.
+- **Simpler single-use semantics:** "a board is played once per player" is a fact about a stored entity, not a rule about seed distribution.
+- Layout size is trivial (a Minesweeper expert board < 1KB).
+
+## Consequences
+- Games recorded before layout storage existed cannot be replayed (archived instead).
+- `game_id` values may appear in URLs → must be unguessable (no sequential IDs).
+- Stored layout data is provided to clients as game rules require.

docs/decisions/README.md

@@ -0,0 +1,14 @@
+# Decision records
+
+Short documents that capture a significant technical decision — its context, the
+choice made, the reasoning, and the consequences. One file per decision, numbered
+and append-only. (This format is commonly called an **Architecture Decision
+Record**, or ADR.)
+
+Records are immutable once accepted. A later decision that changes an earlier one
+is added as a new record that supersedes it, rather than editing the old one — so
+the history of *why* stays intact.
+
+- [0001 — Backend-agnostic package boundary](0001-package-boundary.md)
+- [0002 — Game-agnostic cores behind a game-adapter interface](0002-game-adapter-pattern.md)
+- [0003 — Stored board layouts, not reproducible seeds](0003-stored-boards-not-seeds.md)

eslint.config.js

@@ -50,7 +50,7 @@ export default defineConfig([
     }
   },
   {
-    files: ['scripts/**/*.js'],
+    files: ['**/scripts/**/*.{js,mjs,cjs}'],
     languageOptions: {
       globals: globals.node
     }

leaderboard/leaderboard-element.js

@@ -1,164 +0,0 @@
-import { WebComponent } from 'web-component-base'
-import { LeaderBoardService } from './leader-board.js'
-
-/**
- * `<cozy-leaderboard>` — a custom element that lets a developer compose the
- * leaderboard UI declaratively in HTML instead of wiring it in JavaScript.
- *
- * Built on `web-component-base` (WebComponent base class + lifecycle hooks). It
- * extends WCB for the custom-element scaffolding (onInit/onDestroy, connect
- * handling) and delegates all inner DOM — the duration tabs and the ranked
- * list — to the existing LeaderBoardService, which already builds and manages
- * that DOM (including in-place tab swaps).
- *
- * Composition lives in HTML attributes; the storage backend (adapter) is set
- * once in JS via configureLeaderboard(), because env-var config can't live in
- * static markup.
- *
- *   <cozy-leaderboard category="beginner" title="Best Times" format="time"></cozy-leaderboard>
- */
-
-// Shared config for every element on the page, set once via configureLeaderboard().
-let sharedConfig = {}
-const instances = new Set()
-
-/**
- * Configure the backend + defaults for all <cozy-leaderboard> elements. Call
- * once at startup, after building your adapter (Firebase/Supabase/…). User-facing
- * strings (labels, emptyMessages, loadingText, errorText, anonymousName) can be
- * passed here to localize without changing the package.
- * @param {Object} options - { adapter, scoreOrder?, format?, formatScore?, qualifies?, labels?, emptyMessages?, loadingText?, errorText?, anonymousName? }
- */
-export function configureLeaderboard(options = {}) {
-  sharedConfig = { ...sharedConfig, ...options }
-  instances.forEach(el => el._mount())
-}
-
-const clean = (str, separator) => (str === '00' ? '' : `${str}${separator}`)
-
-// ms -> pretty time, e.g. 4200 -> "04.2" (mirrors utils/timer pretty()).
-const prettyTime = ms => {
-  if (!ms) return '0'
-  const milliseconds = parseInt((ms % 1000) / 100)
-  const seconds = Math.floor((ms / 1000) % 60)
-  const minutes = Math.floor((ms / (1000 * 60)) % 60)
-  const hours = Math.floor((ms / (1000 * 60 * 60)) % 24)
-  const hh = hours < 10 ? `0${hours}` : `${hours}`
-  const mm = minutes < 10 ? `0${minutes}` : `${minutes}`
-  const ss = seconds < 10 ? `0${seconds}` : `${seconds}`
-  return `${clean(hh, ':')}${clean(mm, ':')}${clean(ss, '.')}${milliseconds}`
-}
-
-// Built-in score formatters, selectable via the `format` attribute.
-const FORMATTERS = { time: prettyTime }
-const resolveFormat = name => FORMATTERS[name]
-
-export class CozyLeaderboard extends WebComponent {
-
-  static get observedAttributes() {
-    return ['category', 'title', 'duration', 'score-order', 'format']
-  }
-
-  // WCB lifecycle: register/unregister so configureLeaderboard() can re-render.
-  onInit() {
-    instances.add(this)
-  }
-
-  onDestroy() {
-    instances.delete(this)
-  }
-
-  // Attributes are read directly (getAttribute) rather than through WCB's typed
-  // props proxy, so optional/empty values never trip its type enforcement.
-  attributeChangedCallback(name, previousValue, currentValue) {
-    if (previousValue === currentValue || !this.isConnected) return
-    this._mount(name === 'duration' ? (currentValue || undefined) : undefined)
-  }
-
-  // WCB calls render() on connect; we treat it as "(re)mount the board".
-  render() {
-    this._mount()
-  }
-
-  // Per-element override properties (public): adapter, formatScore, qualifies,
-  // labels, emptyMessages, loadingText, errorText, anonymousName. Each falls back
-  // to the shared configureLeaderboard() value, then the package default. Set
-  // them before the element connects (or clear `_svc` to force a rebuild).
-  _service() {
-    if (this._svc) return this._svc
-    const adapter = this.adapter || sharedConfig.adapter
-    if (!adapter) return null
-    const formatScore = this.formatScore
-      || resolveFormat(this.getAttribute('format'))
-      || sharedConfig.formatScore
-      || resolveFormat(sharedConfig.format)
-      || String
-    this._svc = new LeaderBoardService({
-      adapter,
-      scoreOrder: this.getAttribute('score-order') || sharedConfig.scoreOrder || 'asc',
-      formatScore,
-      qualifies: this.qualifies || sharedConfig.qualifies,
-      // User-facing strings — pass through so apps localize without touching the package.
-      labels: this.labels || sharedConfig.labels,
-      tooltips: this.tooltips || sharedConfig.tooltips,
-      emptyMessages: this.emptyMessages || sharedConfig.emptyMessages,
-      loadingText: this.loadingText || sharedConfig.loadingText,
-      errorText: this.errorText || sharedConfig.errorText,
-      anonymousName: this.anonymousName || sharedConfig.anonymousName
-    })
-    return this._svc
-  }
-
-  /**
-   * (Re)render the board. The first successful mount honors the author's
-   * `duration` attribute; later mounts preserve the service's remembered
-   * duration (so switching category keeps the selected tab) unless a duration
-   * is passed explicitly.
-   */
-  _mount(durationArg) {
-    if (!this.isConnected) return
-    const service = this._service()
-    if (!service) {
-      this.replaceChildren(this._message('Leaderboard not configured.'))
-      return
-    }
-
-    let duration = durationArg
-    if (duration === undefined && !this._mounted) {
-      duration = this.getAttribute('duration') || undefined
-    }
-
-    const token = (this._token || 0) + 1
-    this._token = token
-    service.render(this.getAttribute('category') || '', this.getAttribute('title') || '', duration)
-      .then(el => {
-        if (this._token !== token) return
-        this.replaceChildren(el)
-        this._mounted = true
-      })
-      .catch(() => {
-        if (this._token !== token) return
-        this.replaceChildren(this._message('Leaderboard unavailable right now.'))
-      })
-  }
-
-  /**
-   * Submit a finished game through this element's service — keeps score
-   * submission a one-liner from the host app.
-   * @param {Object} entry
-   */
-  submit(entry) {
-    const service = this._service()
-    if (service) return service.submit(entry)
-  }
-
-  _message(text) {
-    const em = document.createElement('em')
-    em.innerText = text
-    return em
-  }
-}
-
-if (!customElements.get('cozy-leaderboard')) {
-  customElements.define('cozy-leaderboard', CozyLeaderboard)
-}

package.json

@@ -1,8 +1,8 @@
 {
-  "name": "monorepo",
+  "name": "cozy-games",
   "version": "0.0.1",
   "private": true,
-  "description": "Classic Minesweeper browser game",
+  "description": "Cozy Games monorepo — apps, shared packages, and sites",
   "author": "Ayo Ayco",
   "type": "module",
   "repository": {
@@ -12,29 +12,29 @@
   "homepage": "https://mnswpr.com",
   "scripts": {
     "test": "vitest run",
+    "dev": "pnpm -F mnswpr dev",
     "test:watch": "vitest",
-    "dev": "vite app",
+    "build": "pnpm -r --filter \"./packages/*\" run build",
-    "start": "vite app",
+    "build:lib": "vite build packages/mnswpr",
-    "emulators": "npx -y firebase-tools emulators:start --only firestore",
-    "seed:emulator": "cd app && FIRESTORE_EMULATOR_HOST=127.0.0.1:8080 node ../scripts/seed-dev-scores.js",
-    "build": "vite build app",
-    "build:lib": "vite build lib",
     "publish:lib": "node scripts/publish-lib.js",
-    "release": "pnpm build:lib && pnpm -F @ayo-run/mnswpr run release && pnpm publish:lib",
+    "release": "pnpm build:lib && pnpm -F @cozy-games/mnswpr run release && pnpm publish:lib",
-    "build:preview": "pnpm -F app run build:preview",
+    "postinstall": "node scripts/ensure-java.mjs",
     "prepare": "husky",
     "lint": "eslint .",
-    "lint:fix": "eslint . --fix"
+    "lint:fix": "eslint . --fix",
+    "scan:secrets": "secretlint --secretlintignore .secretlintignore \"**/*\""
   },
   "devDependencies": {
     "@eslint/css": "^1.1.0",
     "@eslint/js": "^10.0.1",
+    "@secretlint/secretlint-rule-preset-recommend": "^13.0.2",
     "@stylistic/eslint-plugin": "^5.10.0",
     "bumpp": "^11.0.1",
     "eslint": "^10.1.0",
     "globals": "^17.4.0",
     "husky": "^9.1.7",
     "jsdom": "^29.1.1",
+    "secretlint": "^13.0.2",
     "simple-git": "^3.33.0",
     "vite": "^8.0.3",
     "vitest": "^4.1.9"

packages/leaderboard/CONFIGURATION.md

@@ -103,7 +103,8 @@ mounted elements.
 | `format` | `time` \| `number` \| `plain` | score display preset (below) |
 
 Attributes are reactive: change `category`/`title` at runtime and the board
-re-renders, keeping the selected duration tab.
+re-renders, keeping the selected duration tab. Changing `score-order`/`format`
+rebuilds the element's service so the new order/preset takes effect.
 
 ### `format` presets
 
@@ -230,5 +231,6 @@ The package computes the `day`/`week`/`month` bucket keys from `time_stamp`
 
   The service is cached per element, so set overrides **before** the element
   connects (or set the property and clear the element's `_svc` to force a
-  rebuild). `score-order` and `format` are read from attributes; the function/
+  rebuild — changing the `score-order`/`format` attributes does this
-  array/string overrides are read from properties.
+  automatically). `score-order` and `format` are read from attributes; the
+  function/array/string overrides are read from properties.

packages/leaderboard/README.md

@@ -147,13 +147,63 @@ Want to author your own custom elements this way? Check out
 **[webcomponent.io](https://webcomponent.io)** and
 **[web-component-base](https://github.com/ayo-run/wcb)**.
 
+## Separable read & write surfaces
+
+The service is composed of two independently importable halves, so you never pull
+in code you don't use — and can point each half at a differently-privileged
+backend instance:
+
+| Surface | Import | Uses | Adapter methods |
+| ------- | ------ | ---- | --------------- |
+| **Read / subscribe** | `@cozy-games/leaderboard/leaderboard-read.js` → `LeaderBoardReader` | `render()` — query a window + render the list | `listScores` |
+| **Write** | `@cozy-games/leaderboard/leaderboard-write.js` → `LeaderBoardWriter` | `submit()` — archive + ranked entry | `addScore`, optional `archive`, `getConfig` |
+
+```js
+// Read-only page (public, less-privileged instance) — no write code loaded:
+import { LeaderBoardReader } from '@cozy-games/leaderboard/leaderboard-read.js'
+const board = new LeaderBoardReader({ adapter: readAdapter, formatScore })
+document.body.append(await board.render('beginner', 'Best Times'))
+
+// Server / trusted path (privileged instance) — no DOM or render code loaded:
+import { LeaderBoardWriter } from '@cozy-games/leaderboard/leaderboard-write.js'
+const writer = new LeaderBoardWriter({ adapter: writeAdapter })
+await writer.submit(entry)
+```
+
+The read module imports **no** write-path code (no bucket-key computation, no
+write adapter calls) and the write module imports **no** read/render code (no
+DOM, no `listScores`) — which also keeps each surface trivial to test in
+isolation. `LeaderBoardService` (and `<cozy-leaderboard>`) remain the combined
+facade — same `render()` + `submit()` API — for consumers that want both; it just
+composes a `LeaderBoardReader` and a `LeaderBoardWriter` (exposed as `.reader` /
+`.writer`).
+
 ## Choosing a backend
 
+### Bring your own backend instance (injection)
+
+Both adapters let the **consumer own the backend instance** — including a
+privileged/admin-level or server-side one — rather than the package creating its
+own. This is the injection point per adapter:
+
+| Adapter    | Injection point            | Internal init fallback              |
+| ---------- | -------------------------- | ----------------------------------- |
+| Supabase   | `client` (a supabase-js client you build) — **always** consumer-supplied; the package takes no supabase dependency | none — a client is required |
+| Firebase   | `store` (a Firestore instance you build) | `firebaseConfig` → the package initializes its own app |
+
+Supply a privileged instance and every read/write runs against it — the package
+adds no auth or app lifecycle of its own.
+
 ### Firebase (Firestore)
 
 ```js
 import { FirebaseAdapter } from '@cozy-games/leaderboard/adapters/firebase.js'
+
+// (a) let the package initialize from a public config:
 const adapter = new FirebaseAdapter({ firebaseConfig, namespace: 'mw' })
+
+// (b) OR inject a Firestore instance you built (e.g. privileged/server-side):
+const adapter = new FirebaseAdapter({ store: myFirestore, namespace: 'mw' })
 ```
 
 Needs the `firebase` peer dependency. Uses collections
@@ -162,9 +212,10 @@ Needs the `firebase` peer dependency. Uses collections
 and all-time sorts by `score`, so only Firestore's automatic single-field indexes
 are needed — no composite indexes to deploy.
 
-For local development, pass `emulator` to run against the
+With an injected `store` the package initializes nothing and owns no app
+lifecycle. For internal init, pass `emulator` to run against the
 [Firestore emulator](https://firebase.google.com/docs/emulator-suite) — no cloud,
-no deploy:
+no deploy (wire the emulator into your own store if you inject one):
 
 ```js
 new FirebaseAdapter({ firebaseConfig, namespace: 'mw', emulator: { host: '127.0.0.1', port: 8080 } })

packages/leaderboard/adapters/firebase.js

@@ -12,13 +12,28 @@ import {
 export class FirebaseAdapter {
 
   /**
+   * Supply EITHER a ready Firestore instance via `store` (the injection point —
+   * e.g. a privileged/server-side setup, or an app you already initialized), OR a
+   * `firebaseConfig` for the package to initialize its own app. `store` wins when
+   * both are given; with an injected store the package initializes nothing and
+   * owns no app lifecycle (so `emulator` — a convenience of internal init — is
+   * ignored; wire the emulator into your own store).
+   *
    * @param {Object} options
-   * @param {Object} options.firebaseConfig - Firebase app config (public; access governed by security rules)
+   * @param {Object} [options.store] - a Firestore instance to use as-is (injection point)
+   * @param {Object} [options.firebaseConfig] - Firebase app config for internal init (public; access governed by security rules)
    * @param {String} [options.namespace] - collection prefix
-   * @param {{ host?: string, port?: number }} [options.emulator] - point at a local Firestore emulator (dev/test only)
+   * @param {{ host?: string, port?: number }} [options.emulator] - point the internally-created store at a local Firestore emulator (dev/test only)
    */
   constructor(options = {}) {
     this.namespace = options.namespace || 'lb'
+    if (options.store) {
+      this.store = options.store
+      return
+    }
+    if (!options.firebaseConfig) {
+      throw new TypeError('FirebaseAdapter: provide either `store` (a Firestore instance) or `firebaseConfig`')
+    }
     const app = initializeApp(options.firebaseConfig)
     this.store = getFirestore(app)
     if (options.emulator) {

packages/leaderboard/leader-board.js

@@ -0,0 +1,65 @@
+import { LeaderBoardReader } from './leaderboard-read.js'
+import { LeaderBoardWriter } from './leaderboard-write.js'
+
+/**
+ * Generic, game- AND backend-agnostic leaderboard. Nothing here knows about
+ * minesweeper or Firebase: the ranked value is a plain `score`, sorted in the
+ * configured direction and displayed through an injected formatter, while all
+ * storage I/O is delegated to an injected adapter (see adapters/).
+ *
+ * This is the COMBINED facade: it simply composes the two separable surfaces —
+ * {@link LeaderBoardReader} (read/subscribe/render) and {@link LeaderBoardWriter}
+ * (submit) — for consumers that want both in one object. Consumers who need only
+ * one half import it directly and pull in nothing from the other:
+ *
+ *   import { LeaderBoardReader } from '@cozy-games/leaderboard/leaderboard-read.js'
+ *   import { LeaderBoardWriter } from '@cozy-games/leaderboard/leaderboard-write.js'
+ *
+ * Public API is unchanged: `render()` (read) and `submit()` (write). The reader
+ * and writer are also exposed as `.reader` / `.writer` for direct access. Reads
+ * and writes may be wired to differently-privileged backend instances by passing
+ * the surfaces different adapters (construct a Reader and Writer directly).
+ *
+ * An adapter implements:
+ *   - getConfig(): Promise<Object|undefined>
+ *   - listScores({ category, since, order, limit }): Promise<Object[]>   // read
+ *   - addScore(category, entry): Promise<void>                            // write
+ *   - archive(entry): Promise<void>   // optional personal history        // write
+ */
+export class LeaderBoardService {
+
+  /**
+   * @param {Object} options - see {@link LeaderBoardReader} and {@link LeaderBoardWriter} for the full set
+   * @param {Object} options.adapter - storage backend (e.g. FirebaseAdapter, SupabaseAdapter)
+   * @param {'asc'|'desc'} [options.scoreOrder]
+   * @param {(value: number) => string} [options.formatScore]
+   * @param {(entry: Object) => boolean} [options.qualifies]
+   * @param {Object} [options.labels]
+   * @param {Object} [options.tooltips]
+   * @param {string[]} [options.emptyMessages]
+   * @param {string} [options.loadingText]
+   * @param {string} [options.errorText]
+   * @param {string} [options.anonymousName]
+   */
+  constructor(options = {}) {
+    this.adapter = options.adapter
+    this.reader = new LeaderBoardReader(options)
+    this.writer = new LeaderBoardWriter(options)
+  }
+
+  /**
+   * Read surface — render the ranked list with a duration tab bar.
+   * @see LeaderBoardReader#render
+   */
+  render(category, title, duration) {
+    return this.reader.render(category, title, duration)
+  }
+
+  /**
+   * Write surface — submit a completed game (archive + ranked entry).
+   * @see LeaderBoardWriter#submit
+   */
+  submit(entry) {
+    return this.writer.submit(entry)
+  }
+}

packages/leaderboard/leaderboard-element.js

@@ -0,0 +1,300 @@
+import { WebComponent, html } from 'web-component-base'
+import { LeaderBoardService } from './leader-board.js'
+import { DURATIONS } from './leaderboard-read.js'
+
+/**
+ * `<cozy-leaderboard>` — a custom element that lets a developer compose the
+ * leaderboard UI declaratively in HTML instead of wiring it in JavaScript.
+ *
+ * Built on `web-component-base` (WCB) the idiomatic way: the observed
+ * attributes are declared as `static props` (typed defaults; the base derives
+ * observedAttributes and feeds values into the reactive `this.props`), the view
+ * is a pure `html` template over a precomputed view-state object, and change
+ * reactions arrive through the `onChanges` hook. Data access and user-facing
+ * strings stay in {@link LeaderBoardService} / LeaderBoardReader — the element
+ * only turns query results into templates.
+ *
+ * (WCB ≥5 is required: v4 wrote each prop default onto the element as an
+ * attribute inside the constructor, which the custom-elements spec forbids and
+ * which broke `document.createElement('cozy-leaderboard')`. v5 defers that
+ * reflection to connect and never clobbers authored attributes, making
+ * `static props` safe here.)
+ *
+ * Composition lives in HTML attributes; the storage backend (adapter) is set
+ * once in JS via configureLeaderboard(), because env-var config can't live in
+ * static markup.
+ *
+ *   <cozy-leaderboard category="beginner" title="Best Times" format="time"></cozy-leaderboard>
+ */
+
+// Shared config for every element on the page, set once via configureLeaderboard().
+let sharedConfig = {}
+const instances = new Set()
+
+/**
+ * Configure the backend + defaults for all <cozy-leaderboard> elements. Call
+ * once at startup, after building your adapter (Firebase/Supabase/…). User-facing
+ * strings (labels, emptyMessages, loadingText, errorText, anonymousName) can be
+ * passed here to localize without changing the package.
+ * @param {Object} options - { adapter, scoreOrder?, format?, formatScore?, qualifies?, labels?, emptyMessages?, loadingText?, errorText?, anonymousName? }
+ */
+export function configureLeaderboard(options = {}) {
+  sharedConfig = { ...sharedConfig, ...options }
+  instances.forEach(el => el._mount())
+}
+
+const clean = (str, separator) => (str === '00' ? '' : `${str}${separator}`)
+
+// ms -> pretty time, e.g. 4200 -> "04.2" (mirrors utils/timer pretty()).
+const prettyTime = ms => {
+  if (!ms) return '0'
+  const milliseconds = parseInt((ms % 1000) / 100)
+  const seconds = Math.floor((ms / 1000) % 60)
+  const minutes = Math.floor((ms / (1000 * 60)) % 60)
+  const hours = Math.floor((ms / (1000 * 60 * 60)) % 24)
+  const hh = hours < 10 ? `0${hours}` : `${hours}`
+  const mm = minutes < 10 ? `0${minutes}` : `${minutes}`
+  const ss = seconds < 10 ? `0${seconds}` : `${seconds}`
+  return `${clean(hh, ':')}${clean(mm, ':')}${clean(ss, '.')}${milliseconds}`
+}
+
+// Built-in score formatters, selectable via the `format` attribute.
+const FORMATTERS = { time: prettyTime }
+const resolveFormat = name => FORMATTERS[name]
+
+// Inline styles (as WCB `html` style objects) — the same visual output the
+// LeaderBoardReader produces for the imperative JS composition path.
+const STYLES = {
+  wrapper: { maxWidth: '270px', margin: '0 auto' },
+  heading: { borderBottom: '1px solid #c0c0c0', paddingBottom: '10px' },
+  tabBar: { display: 'flex', justifyContent: 'center', gap: '8px', marginBottom: '10px' },
+  list: { listStyle: 'none', textAlign: 'left' },
+  row: { display: 'flex' },
+  name: {
+    textOverflow: 'ellipsis',
+    whiteSpace: 'nowrap',
+    overflow: 'hidden',
+    padding: '0 5px',
+    fontWeight: 'bold',
+    fontStyle: 'italic',
+    flex: '1'
+  }
+}
+
+const tabStyle = active => ({
+  background: 'none',
+  border: 'none',
+  cursor: 'pointer',
+  padding: '2px 4px',
+  fontSize: '0.85em',
+  color: active ? '#ffffff' : '#999999',
+  fontWeight: active ? 'bold' : 'normal',
+  borderBottom: active ? '2px solid orange' : '2px solid transparent'
+})
+
+export class CozyLeaderboard extends WebComponent {
+
+  // Declared attributes (kebab-cased on the element: score-order). String
+  // defaults keep `this.props.*` typed as strings, so an unset or emptied
+  // attribute reads as '' rather than a coerced boolean. The base class derives
+  // observedAttributes from these keys.
+  static props = {
+    category: '',
+    title: '',
+    duration: '',
+    scoreOrder: '',
+    format: ''
+  }
+
+  // View state the template renders from. Either { board: false } (not
+  // configured) or { board: true, tabs, active, list } where list is
+  // { rows: [{ index, name, score }] } or { message } (loading/empty/error).
+  _view = { board: false }
+  // Selected duration window; survives category changes and re-connects.
+  // null until the board first mounts, so the `duration` attribute is honored.
+  _activeDuration = null
+  _connected = false
+  _token = 0
+
+  // WCB lifecycle: connect mounts the board, disconnect unregisters. The
+  // instances set lets configureLeaderboard() re-mount live elements.
+  onInit() {
+    this._connected = true
+    instances.add(this)
+    this._mount()
+  }
+
+  onDestroy() {
+    this._connected = false
+    instances.delete(this)
+  }
+
+  /**
+   * WCB change hook — `property` is the camelCase prop name (WCB ≥5). A title
+   * change needs no re-query: the heading reads `this.props.title`, so the base
+   * class's own render already updated it. score-order/format changes rebuild
+   * the service so the new config actually takes effect.
+   */
+  onChanges({ property }) {
+    // Invalidate the cached service even while disconnected, so a scoreOrder/
+    // format change made on a detached element takes effect on re-connect.
+    if (property === 'scoreOrder' || property === 'format') this._svc = null
+    if (!this._connected || property === 'title') return
+    this._mount(property === 'duration' ? (this.props.duration || undefined) : undefined)
+  }
+
+  get template() {
+    const view = this._view
+    if (!view.board) return html`<em>Leaderboard not configured.</em>`
+    return html`
+      <div style=${STYLES.wrapper}>
+        <h3 style=${STYLES.heading}>${this.props.title}</h3>
+        <div style=${STYLES.tabBar}>
+          ${view.tabs.map(tab => html`
+            <button
+              type="button"
+              title=${tab.tooltip}
+              data-duration=${tab.id}
+              style=${tabStyle(tab.id === view.active)}
+              onclick=${() => this._selectTab(tab.id)}
+            >${tab.label}</button>
+          `)}
+        </div>
+        <div>
+          ${view.list.rows
+            ? html`
+              <div style=${STYLES.list}>
+                ${view.list.rows.map(row => html`
+                  <div style=${STYLES.row}>
+                    <div>#${row.index}</div>
+                    <div title=${row.name} style=${STYLES.name}>${row.name}</div>
+                    <div>${row.score}</div>
+                  </div>
+                `)}
+              </div>`
+            : html`<em>${view.list.message}</em>`}
+        </div>
+      </div>
+    `
+  }
+
+  // Per-element override properties (public): adapter, formatScore, qualifies,
+  // labels, tooltips, emptyMessages, loadingText, errorText, anonymousName.
+  // Each falls back to the shared configureLeaderboard() value, then the
+  // package default. Set them before the element connects (or clear `_svc` to
+  // force a rebuild). Rich values stay plain properties — WCB props are
+  // attribute-backed and only carry serializable primitives.
+  _service() {
+    if (this._svc) return this._svc
+    const adapter = this.adapter || sharedConfig.adapter
+    if (!adapter) return null
+    const formatScore = this.formatScore
+      || resolveFormat(this.props.format)
+      || sharedConfig.formatScore
+      || resolveFormat(sharedConfig.format)
+      || String
+    this._svc = new LeaderBoardService({
+      adapter,
+      scoreOrder: this.props.scoreOrder || sharedConfig.scoreOrder || 'asc',
+      formatScore,
+      qualifies: this.qualifies || sharedConfig.qualifies,
+      // User-facing strings — pass through so apps localize without touching the package.
+      labels: this.labels || sharedConfig.labels,
+      tooltips: this.tooltips || sharedConfig.tooltips,
+      emptyMessages: this.emptyMessages || sharedConfig.emptyMessages,
+      loadingText: this.loadingText || sharedConfig.loadingText,
+      errorText: this.errorText || sharedConfig.errorText,
+      anonymousName: this.anonymousName || sharedConfig.anonymousName
+    })
+    return this._svc
+  }
+
+  /**
+   * (Re)mount the board. The first mount honors the author's `duration`
+   * attribute; later mounts keep the selected duration (so switching category
+   * keeps the selected tab) unless a duration is passed explicitly.
+   */
+  _mount(durationArg) {
+    if (!this._connected) return
+    const service = this._service()
+    if (!service) {
+      this._view = { board: false }
+      this._paint()
+      return
+    }
+    const duration = durationArg
+      ?? this._activeDuration
+      ?? (this.props.duration || 'today')
+    this._activeDuration = duration
+    this._load(service, duration)
+  }
+
+  _selectTab(id) {
+    this._activeDuration = id
+    this._load(this._service(), id)
+  }
+
+  /**
+   * Query one duration window and project the result into view state: a
+   * loading message immediately, then rows / a random empty message / the
+   * error text. The token guards against a stale response (quick tab or
+   * category switches) overwriting a newer one.
+   */
+  async _load(service, durationId) {
+    const reader = service.reader
+    const tabs = DURATIONS.map(d => ({ id: d.id, label: reader.label(d), tooltip: reader.tooltip(d) }))
+    const board = list => ({ board: true, tabs, active: durationId, list })
+
+    const token = ++this._token
+    this._view = board({ message: reader.loadingText })
+    this._paint()
+
+    let list
+    try {
+      const rows = await reader.list(this.props.category, durationId)
+      list = (rows && rows.length)
+        ? {
+          rows: rows.map((row, index) => ({
+            index: index + 1,
+            name: row.name || reader.anonymousName,
+            score: reader.formatScore(row.score)
+          }))
+        }
+        : { message: reader.emptyMessage() }
+    } catch {
+      list = { message: reader.errorText }
+    }
+    if (token !== this._token) return
+    this._view = board(list)
+    this._paint()
+  }
+
+  /**
+   * Render the current view state through WCB. WCB's render() replaces the
+   * whole subtree (no diffing yet), which would drop focus from a clicked
+   * duration tab — the one behavior the base class can't preserve for us — so
+   * focus is handed to the replacement tab explicitly.
+   */
+  _paint() {
+    // getRootNode(), not document: inside a shadow root, document.activeElement
+    // is retargeted to the host and the focused tab would go undetected.
+    const focused = this.getRootNode().activeElement
+    const focusedTab = focused && this.contains(focused) ? focused.dataset.duration : undefined
+    this.render()
+    if (focusedTab) this.querySelector(`button[data-duration="${focusedTab}"]`)?.focus()
+  }
+
+  /**
+   * Submit a finished game through this element's service — keeps score
+   * submission a one-liner from the host app.
+   * @param {Object} entry
+   */
+  submit(entry) {
+    const service = this._service()
+    if (service) return service.submit(entry)
+  }
+}
+
+if (!customElements.get('cozy-leaderboard')) {
+  customElements.define('cozy-leaderboard', CozyLeaderboard)
+}

packages/leaderboard/leaderboard-read.js

@@ -1,4 +1,12 @@
-import { buckets } from '../utils/date-bucket/date-bucket.js'
+/**
+ * The READ / subscribe surface of the leaderboard: querying a time window and
+ * rendering the ranked list. Importable WITHOUT any write-path code — no
+ * `submit`, no bucket-key computation, no write adapter calls — so read-only
+ * consumers (and tests) pull in nothing they don't need.
+ *
+ * Pairs with `leaderboard-write.js` (the write half) and `leader-board.js` (the
+ * combined facade). The READ side only ever calls `adapter.listScores`.
+ */
 
 const DAY_MS = 24 * 60 * 60 * 1000
 
@@ -6,9 +14,10 @@ const DAY_MS = 24 * 60 * 60 * 1000
  * The four time windows are ROLLING: each shows entries from the last `ms`
  * milliseconds (strictly nested — 24h ⊆ 7d ⊆ 30d ⊆ all), sorted by score.
  * `ms: null` is the all-time view (no time filter). `title` is the hover tooltip
- * that spells out the window.
+ * that spells out the window. Exported so view layers (e.g. the
+ * `<cozy-leaderboard>` element) can render the tab bar themselves.
  */
-const DURATIONS = [
+export const DURATIONS = [
   { id: 'today', label: 'Today', ms: DAY_MS, title: 'Last 24 hours' },
   { id: 'week', label: 'Week', ms: 7 * DAY_MS, title: 'Last 7 days' },
   { id: 'month', label: 'Month', ms: 30 * DAY_MS, title: 'Last 30 days' },
@@ -18,7 +27,7 @@ const DURATIONS = [
 /**
  * Default empty-state messages — challenging but friendly, and game-agnostic.
  * One is picked at random each render. Override per app via the `emptyMessages`
- * option (see below) so localization stays out of this package.
+ * option so localization stays out of this package.
  */
 const EMPTY_MESSAGES = [
   'Be the first to enter the leader board!',
@@ -32,26 +41,18 @@ const EMPTY_MESSAGES = [
 ]
 
 /**
- * Generic, game- AND backend-agnostic leaderboard. Nothing here knows about
+ * Read-only leaderboard view: windows, sorting (via the adapter), and rendering.
- * minesweeper or Firebase: the ranked value is a plain `score`, sorted in the
+ * Nothing here writes; the ranked value is a plain `score` displayed through an
- * configured direction and displayed through an injected formatter, while all
+ * injected formatter, and all query I/O is delegated to an injected adapter's
- * storage I/O is delegated to an injected adapter (see adapters/). Games wire
+ * `listScores`. Safe to wire to a read-only / less-privileged backend instance.
- * their specifics through the constructor options.
- *
- * An adapter implements:
- *   - getConfig(): Promise<Object|undefined>
- *   - listScores({ category, field, value, order, limit }): Promise<Object[]>
- *   - addScore(category, entry): Promise<void>
- *   - archive(entry): Promise<void>   // optional personal history
  */
-export class LeaderBoardService {
+export class LeaderBoardReader {
 
   /**
    * @param {Object} options
-   * @param {Object} options.adapter - storage backend (e.g. FirebaseAdapter, SupabaseAdapter)
+   * @param {Object} options.adapter - storage backend; the READ side uses `listScores`
    * @param {'asc'|'desc'} [options.scoreOrder] - 'asc' = lower is better (e.g. time), 'desc' = higher is better
    * @param {(value: number) => string} [options.formatScore] - display formatter for a score
-   * @param {(entry: Object) => boolean} [options.qualifies] - whether an entry is ranked; defaults to server passingStatus vs entry.status
    * @param {Object} [options.labels] - optional tab-label overrides keyed by duration id
    * @param {Object} [options.tooltips] - optional tab hover-text overrides keyed by duration id
    * @param {string[]} [options.emptyMessages] - empty-state messages (one picked at random); localize here
@@ -63,7 +64,6 @@ export class LeaderBoardService {
     this.adapter = options.adapter
     this.scoreOrder = options.scoreOrder === 'desc' ? 'desc' : 'asc'
     this.formatScore = options.formatScore || (value => String(value))
-    this.qualifies = options.qualifies || (entry => this._defaultQualifies(entry))
     this.labels = options.labels || {}
     this.tooltips = options.tooltips || {}
 
@@ -74,36 +74,42 @@ export class LeaderBoardService {
     this.loadingText = options.loadingText || 'Loading…'
     this.errorText = options.errorText || 'Leaderboard unavailable right now.'
     this.anonymousName = options.anonymousName || 'Anonymous'
-
-    Promise.resolve(this.adapter.getConfig())
-      .then(config => {
-        this.configuration = config
-      })
-      .catch(() => {})
   }
 
   /**
-   * Default ranking gate: if the server config names a `passingStatus`, only
+   * Display label for a duration window (override-aware).
-   * entries whose `status` matches qualify; otherwise every entry qualifies.
+   * @param {{ id: String, label: String }} duration - a DURATIONS entry
    */
-  _defaultQualifies(entry) {
+  label(duration) {
-    const passing = this.configuration && this.configuration.passingStatus
-    if (!passing) return true
-    return entry.status === passing
-  }
-
-  _label(duration) {
     return this.labels[duration.id] || duration.label
   }
 
-  _tooltip(duration) {
+  /**
+   * Hover tooltip for a duration window (override-aware).
+   * @param {{ id: String, title: String }} duration - a DURATIONS entry
+   */
+  tooltip(duration) {
     return this.tooltips[duration.id] || duration.title
   }
 
-  _emptyMessage() {
+  /** One empty-state message, picked at random. */
+  emptyMessage() {
     return this.emptyMessages[Math.floor(Math.random() * this.emptyMessages.length)]
   }
 
+  /**
+   * Data-level query: the ranked entries for a category and duration window,
+   * without any DOM. View layers that render themselves (e.g. the
+   * `<cozy-leaderboard>` element) use this instead of {@link render}.
+   * @param {String} category
+   * @param {String} durationId - a DURATIONS id ('today' | 'week' | 'month' | 'all')
+   * @returns {Promise<Object[]>}
+   */
+  async list(category, durationId) {
+    const duration = DURATIONS.find(d => d.id === durationId)
+    return this.adapter.listScores(this._descriptor(category, duration))
+  }
+
   /**
    * Backend-neutral query descriptor for a category and time window. `since` is
    * the rolling cutoff (entries with `time_stamp >= since`); `null` means
@@ -140,7 +146,7 @@ export class LeaderBoardService {
     wrapper.style.margin = '0 auto'
 
     const heading = document.createElement('h3')
-    heading.innerText = title
+    heading.textContent = title
     heading.style.borderBottom = '1px solid #c0c0c0'
     heading.style.paddingBottom = '10px'
     wrapper.append(heading)
@@ -164,9 +170,9 @@ export class LeaderBoardService {
 
     DURATIONS.forEach(d => {
       const tab = document.createElement('button')
-      tab.innerText = this._label(d)
+      tab.textContent = this.label(d)
       tab.type = 'button'
-      tab.setAttribute('title', this._tooltip(d))
+      tab.setAttribute('title', this.tooltip(d))
       this._styleTab(tab, d.id === duration)
       tab.onclick = () => activate(d.id)
       tabs[d.id] = tab
@@ -203,7 +209,7 @@ export class LeaderBoardService {
 
     listWrapper.innerHTML = ''
     const loading = document.createElement('em')
-    loading.innerText = this.loadingText
+    loading.textContent = this.loadingText
     listWrapper.append(loading)
 
     try {
@@ -214,7 +220,7 @@ export class LeaderBoardService {
       if (this._loadToken !== token) return
       listWrapper.innerHTML = ''
       const message = document.createElement('em')
-      message.innerText = this.errorText
+      message.textContent = this.errorText
       listWrapper.append(message)
     }
   }
@@ -224,7 +230,7 @@ export class LeaderBoardService {
 
     if (!rows || !rows.length) {
       const message = document.createElement('em')
-      message.innerText = this._emptyMessage()
+      message.textContent = this.emptyMessage()
       listWrapper.append(message)
       return
     }
@@ -239,11 +245,12 @@ export class LeaderBoardService {
       item.style.display = 'flex'
 
       const indexElement = document.createElement('div')
-      indexElement.innerText = `#${i++}`
+      indexElement.textContent = `#${i++}`
 
       const nameElement = document.createElement('div')
       const name = data.name || this.anonymousName
-      nameElement.innerHTML = name
+      // textContent, never innerHTML: names are player-controlled input.
+      nameElement.textContent = name
       nameElement.setAttribute('title', name)
       nameElement.style.textOverflow = 'ellipsis'
       nameElement.style.whiteSpace = 'nowrap'
@@ -254,7 +261,7 @@ export class LeaderBoardService {
       nameElement.style.flex = '1'
 
       const scoreElement = document.createElement('div')
-      scoreElement.innerText = this.formatScore(data.score)
+      scoreElement.textContent = this.formatScore(data.score)
 
       item.append(indexElement, nameElement, scoreElement)
       list.append(item)
@@ -262,41 +269,4 @@ export class LeaderBoardService {
 
     listWrapper.append(list)
   }
-
-  /**
-   * Submit a completed game. Always archives it (personal history); if it
-   * qualifies, also writes a ranked entry with denormalized bucket keys. Both
-   * writes go through the adapter, so the storage backend is pluggable. The
-   * caller owns display-name/nickname UX.
-   * @param {Object} entry - { name, playerId, score, category, time_stamp, status?, meta? }
-   */
-  async submit(entry) {
-    if (this.adapter.archive) {
-      await this.adapter.archive({
-        playerId: entry.playerId,
-        score: entry.score,
-        category: entry.category,
-        time_stamp: entry.time_stamp,
-        meta: entry.meta
-      })
-    }
-
-    if (!this.qualifies(entry)) return
-
-    const stamp = entry.time_stamp instanceof Date ? entry.time_stamp : new Date(entry.time_stamp)
-    const bucket = buckets(stamp)
-    const scoreDoc = {
-      name: entry.name || 'Anonymous',
-      playerId: entry.playerId,
-      score: entry.score,
-      category: entry.category,
-      time_stamp: entry.time_stamp,
-      day: bucket.day,
-      week: bucket.week,
-      month: bucket.month
-    }
-    if (entry.meta) scoreDoc.meta = entry.meta
-
-    await this.adapter.addScore(entry.category, scoreDoc)
-  }
 }

packages/leaderboard/leaderboard-write.js

@@ -0,0 +1,80 @@
+import { buckets } from '@cozy-games/utils/date-bucket/date-bucket.js'
+
+/**
+ * The WRITE surface of the leaderboard: submitting a completed game — the
+ * personal archive plus, if it qualifies, a ranked entry with denormalized
+ * day/week/month bucket keys. Importable WITHOUT any read/render code — no DOM,
+ * no list rendering, no `listScores` — so a consumer can wire writes to a
+ * separate, more-privileged backend instance (leaderboard-01) and pull in none
+ * of the read surface.
+ *
+ * The WRITE side calls `adapter.archive` (optional) and `adapter.addScore`; it
+ * also reads the ranking `config` once (an adapter call, not read/render code)
+ * to power the default qualifier.
+ */
+export class LeaderBoardWriter {
+
+  /**
+   * @param {Object} options
+   * @param {Object} options.adapter - storage backend; the WRITE side uses `addScore`, optional `archive`, and `getConfig`
+   * @param {(entry: Object) => boolean} [options.qualifies] - whether an entry is ranked; defaults to server passingStatus vs entry.status
+   */
+  constructor(options = {}) {
+    this.adapter = options.adapter
+    this.qualifies = options.qualifies || (entry => this._defaultQualifies(entry))
+
+    // The default qualifier depends on the server's ranking config, so load it
+    // once. This is a config READ via the adapter — it pulls in no read/render
+    // module, keeping the write surface importable on its own.
+    Promise.resolve(this.adapter && this.adapter.getConfig ? this.adapter.getConfig() : undefined)
+      .then(config => { this.configuration = config })
+      .catch(() => {})
+  }
+
+  /**
+   * Default ranking gate: if the server config names a `passingStatus`, only
+   * entries whose `status` matches qualify; otherwise every entry qualifies.
+   */
+  _defaultQualifies(entry) {
+    const passing = this.configuration && this.configuration.passingStatus
+    if (!passing) return true
+    return entry.status === passing
+  }
+
+  /**
+   * Submit a completed game. Always archives it (personal history); if it
+   * qualifies, also writes a ranked entry with denormalized bucket keys. Both
+   * writes go through the adapter, so the storage backend is pluggable. The
+   * caller owns display-name/nickname UX.
+   * @param {Object} entry - { name, playerId, score, category, time_stamp, status?, meta? }
+   */
+  async submit(entry) {
+    if (this.adapter.archive) {
+      await this.adapter.archive({
+        playerId: entry.playerId,
+        score: entry.score,
+        category: entry.category,
+        time_stamp: entry.time_stamp,
+        meta: entry.meta
+      })
+    }
+
+    if (!this.qualifies(entry)) return
+
+    const stamp = entry.time_stamp instanceof Date ? entry.time_stamp : new Date(entry.time_stamp)
+    const bucket = buckets(stamp)
+    const scoreDoc = {
+      name: entry.name || 'Anonymous',
+      playerId: entry.playerId,
+      score: entry.score,
+      category: entry.category,
+      time_stamp: entry.time_stamp,
+      day: bucket.day,
+      week: bucket.week,
+      month: bucket.month
+    }
+    if (entry.meta) scoreDoc.meta = entry.meta
+
+    await this.adapter.addScore(entry.category, scoreDoc)
+  }
+}

packages/leaderboard/package.json

@@ -9,6 +9,9 @@
     "url": "https://github.com/ayo-run/mnswpr"
   },
   "main": "leader-board.js",
+  "scripts": {
+    "build": "vite build"
+  },
   "exports": {
     ".": {
       "default": "./dist/leader-board.js"
@@ -25,7 +28,10 @@
     "./dist"
   ],
   "dependencies": {
-    "web-component-base": "^4.1.2"
+    "web-component-base": "^5.0.0"
+  },
+  "devDependencies": {
+    "@cozy-games/utils": "workspace:*"
   },
   "peerDependencies": {
     "firebase": "^12.11.0"

packages/leaderboard/test/firebase-adapter.test.js

@@ -0,0 +1,102 @@
+// @ts-check
+import { describe, it, expect, beforeEach, vi } from 'vitest'
+
+// Stub the firebase SDK at the adapter boundary so no real app/network is touched.
+const fb = vi.hoisted(() => ({
+  initializeApp: vi.fn(() => ({ __app: true })),
+  getFirestore: vi.fn(() => ({ __internalStore: true })),
+  connectFirestoreEmulator: vi.fn(),
+  doc: vi.fn((...args) => ({ __ref: args })),
+  getDoc: vi.fn(async () => ({ data: () => ({ passingStatus: 'ok' }) })),
+  getDocs: vi.fn(async () => ({ docs: [] })),
+  setDoc: vi.fn(async () => {}),
+  collection: vi.fn((...args) => ({ __col: args })),
+  query: vi.fn((...args) => ({ __q: args })),
+  where: vi.fn((...args) => ({ __where: args })),
+  orderBy: vi.fn((...args) => ({ __order: args })),
+  limit: vi.fn((...args) => ({ __limit: args }))
+}))
+
+vi.mock('firebase/app', () => ({ initializeApp: fb.initializeApp }))
+vi.mock('firebase/firestore/lite', () => ({
+  getFirestore: fb.getFirestore,
+  connectFirestoreEmulator: fb.connectFirestoreEmulator,
+  doc: fb.doc,
+  getDoc: fb.getDoc,
+  getDocs: fb.getDocs,
+  setDoc: fb.setDoc,
+  collection: fb.collection,
+  query: fb.query,
+  where: fb.where,
+  orderBy: fb.orderBy,
+  limit: fb.limit
+}))
+
+import { FirebaseAdapter } from '../adapters/firebase.js'
+
+beforeEach(() => vi.clearAllMocks())
+
+describe('FirebaseAdapter — consumer-supplied (injected) store', () => {
+  it('uses an injected store as-is and initializes nothing', () => {
+    // Stand-in for a privileged / server-side Firestore instance.
+    const store = { __adminStore: true }
+    const adapter = new FirebaseAdapter({ store, namespace: 'mw' })
+    expect(adapter.store).toBe(store)
+    expect(fb.initializeApp).not.toHaveBeenCalled()
+    expect(fb.getFirestore).not.toHaveBeenCalled()
+  })
+
+  it('performs a write through the injected store', async () => {
+    const store = { __adminStore: true }
+    const adapter = new FirebaseAdapter({ store, namespace: 'mw' })
+    const entry = { name: 'A', score: 42, category: 'beginner', time_stamp: 123 }
+
+    await adapter.addScore('beginner', entry)
+
+    // The collection was built from OUR store, and the entry was written.
+    expect(fb.collection).toHaveBeenCalledWith(store, 'mw-scores', 'beginner', 'games')
+    expect(fb.setDoc).toHaveBeenCalledTimes(1)
+    expect(fb.setDoc.mock.calls[0][1]).toEqual(entry)
+  })
+
+  it('archives through the injected store', async () => {
+    const store = { __adminStore: true }
+    const adapter = new FirebaseAdapter({ store, namespace: 'mw' })
+    await adapter.archive({ playerId: 'p1', score: 9, category: 'beginner', time_stamp: 5 })
+    expect(fb.doc).toHaveBeenCalledWith(store, 'mw-all', 'p1', 'games', expect.any(String))
+    expect(fb.setDoc).toHaveBeenCalledTimes(1)
+  })
+
+  it('does not auto-connect the emulator for an injected store (consumer owns it)', () => {
+    new FirebaseAdapter({ store: { __s: 1 }, namespace: 'mw', emulator: { host: 'x', port: 1 } })
+    expect(fb.connectFirestoreEmulator).not.toHaveBeenCalled()
+  })
+
+  it('prefers the injected store when both store and firebaseConfig are given', () => {
+    const store = { __adminStore: true }
+    const adapter = new FirebaseAdapter({ store, firebaseConfig: { projectId: 'p' } })
+    expect(adapter.store).toBe(store)
+    expect(fb.initializeApp).not.toHaveBeenCalled()
+  })
+})
+
+describe('FirebaseAdapter — internal init (existing path, unbroken)', () => {
+  it('still initializes its own store from firebaseConfig and writes', async () => {
+    const adapter = new FirebaseAdapter({ firebaseConfig: { projectId: 'p' }, namespace: 'mw' })
+    expect(fb.initializeApp).toHaveBeenCalledWith({ projectId: 'p' })
+    expect(fb.getFirestore).toHaveBeenCalledTimes(1)
+    expect(adapter.store).toEqual({ __internalStore: true })
+
+    await adapter.addScore('beginner', { score: 1 })
+    expect(fb.setDoc).toHaveBeenCalledTimes(1)
+  })
+
+  it('still connects the emulator when configured', () => {
+    new FirebaseAdapter({ firebaseConfig: {}, emulator: { host: '127.0.0.1', port: 8080 } })
+    expect(fb.connectFirestoreEmulator).toHaveBeenCalledWith({ __internalStore: true }, '127.0.0.1', 8080)
+  })
+
+  it('throws a clear error when neither store nor firebaseConfig is given', () => {
+    expect(() => new FirebaseAdapter({})).toThrow(TypeError)
+  })
+})

packages/leaderboard/test/leaderboard-element.test.js

@@ -0,0 +1,592 @@
+// @ts-check
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+
+import { configureLeaderboard } from '../leaderboard-element.js'
+
+/**
+ * Characterization tests for <cozy-leaderboard>: every externally observable
+ * behavior of the element, written against the element's public surface only
+ * (attributes, properties, produced DOM, adapter calls) so the implementation
+ * can be refactored while this suite stays green.
+ *
+ * Two behaviors are deliberately NOT pinned here:
+ *  - entry names render via innerHTML today (an XSS hazard); only the text is
+ *    asserted, so a safe text rendering also passes.
+ *  - score-order / format attribute CHANGES after the first mount are silently
+ *    ignored today (the per-element service caches its config); honoring them
+ *    is an allowed improvement.
+ */
+
+const DEFAULT_EMPTY_MESSAGES = [
+  'Be the first to enter the leader board!',
+  'No scores yet — claim the top spot!',
+  'This board is wide open. Conquer it!',
+  'No champions here yet. Will it be you?',
+  'Blank slate — set the score to beat!',
+  'Nobody\'s here yet. Be the first!',
+  'The top spot is up for grabs. Take it!',
+  'Empty board. Time to make your mark!'
+]
+
+const makeAdapter = (rows = [], overrides = {}) => ({
+  listScores: vi.fn(async () => rows),
+  addScore: vi.fn(async () => {}),
+  archive: vi.fn(async () => {}),
+  getConfig: vi.fn(async () => undefined),
+  ...overrides
+})
+
+// Reset every shared-config key; `undefined` falls through all fallback chains.
+const resetSharedConfig = () => configureLeaderboard({
+  adapter: undefined,
+  scoreOrder: undefined,
+  format: undefined,
+  formatScore: undefined,
+  qualifies: undefined,
+  labels: undefined,
+  tooltips: undefined,
+  emptyMessages: undefined,
+  loadingText: undefined,
+  errorText: undefined,
+  anonymousName: undefined
+})
+
+/**
+ * Create a disconnected element, apply attributes and per-element override
+ * properties (they must be set before connect), then connect it — the
+ * documented composition flow.
+ */
+const mount = (attrs = {}, props = {}) => {
+  const el = /** @type {any} */ (document.createElement('cozy-leaderboard'))
+  Object.entries(attrs).forEach(([name, value]) => el.setAttribute(name, value))
+  Object.assign(el, props)
+  document.body.append(el)
+  return el
+}
+
+const tabButtons = el => [...el.querySelectorAll('button')]
+const tabByLabel = (el, label) => tabButtons(el).find(b => b.textContent === label)
+const rowsText = el => el.textContent
+
+beforeEach(() => resetSharedConfig())
+afterEach(() => { document.body.innerHTML = '' })
+
+describe('unconfigured state', () => {
+  it('renders the not-configured message when no adapter exists anywhere', async () => {
+    const el = mount({ category: 'beginner', title: 'Best Times' })
+    await vi.waitFor(() => {
+      const em = el.querySelector('em')
+      expect(em).toBeTruthy()
+      expect(em.textContent).toBe('Leaderboard not configured.')
+    })
+  })
+
+  it('mounts the board when configureLeaderboard() supplies an adapter later', async () => {
+    const el = mount({ category: 'beginner', title: 'Best Times' })
+    await vi.waitFor(() => expect(el.textContent).toContain('Leaderboard not configured.'))
+
+    const adapter = makeAdapter([{ name: 'Ada', score: 3 }])
+    configureLeaderboard({ adapter })
+    await vi.waitFor(() => {
+      expect(el.querySelector('h3')).toBeTruthy()
+      expect(rowsText(el)).toContain('Ada')
+    })
+  })
+})
+
+describe('board structure', () => {
+  it('renders heading, four duration tabs with tooltips, and ranked rows', async () => {
+    const adapter = makeAdapter([
+      { name: 'Ada', score: 3 },
+      { name: 'Bo', score: 5 }
+    ])
+    const el = mount({ category: 'beginner', title: 'Best Times' }, { adapter })
+
+    await vi.waitFor(() => expect(rowsText(el)).toContain('Ada'))
+
+    const heading = el.querySelector('h3')
+    expect(heading.textContent).toBe('Best Times')
+
+    const tabs = tabButtons(el)
+    expect(tabs.map(t => t.textContent)).toEqual(['Today', 'Week', 'Month', 'All Time'])
+    expect(tabs.map(t => t.getAttribute('title'))).toEqual([
+      'Last 24 hours', 'Last 7 days', 'Last 30 days', 'All time'
+    ])
+    tabs.forEach(t => expect(t.type).toBe('button'))
+
+    // Ranked rows: index, name (with hover title), formatted score.
+    expect(rowsText(el)).toContain('#1')
+    expect(rowsText(el)).toContain('#2')
+    expect(rowsText(el)).toContain('3')
+    expect(rowsText(el)).toContain('5')
+    const nameCells = [...el.querySelectorAll('[title="Ada"], [title="Bo"]')]
+    expect(nameCells).toHaveLength(2)
+  })
+
+  it('shows the loading text while the query is in flight', async () => {
+    let resolve
+    const adapter = makeAdapter([], {
+      listScores: vi.fn(() => new Promise(r => { resolve = r }))
+    })
+    const el = mount({ category: 'beginner', title: 'Best Times' }, { adapter })
+
+    await vi.waitFor(() => expect(rowsText(el)).toContain('Loading…'))
+    expect(el.querySelector('h3')).toBeTruthy() // heading + tabs render before data
+
+    resolve([{ name: 'Ada', score: 3 }])
+    await vi.waitFor(() => expect(rowsText(el)).toContain('Ada'))
+    expect(rowsText(el)).not.toContain('Loading…')
+  })
+
+  it('marks the active tab and leaves the others inactive', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'Best Times' }, { adapter })
+    await vi.waitFor(() => expect(tabButtons(el)).toHaveLength(4))
+
+    const today = tabByLabel(el, 'Today')
+    const week = tabByLabel(el, 'Week')
+    expect(today.style.fontWeight).toBe('bold')
+    expect(today.style.borderBottom).toContain('orange')
+    expect(week.style.fontWeight).toBe('normal')
+    expect(week.style.borderBottom).toContain('transparent')
+  })
+})
+
+describe('queries', () => {
+  it('queries the \'today\' rolling window by default, limited to 10', async () => {
+    const adapter = makeAdapter([])
+    mount({ category: 'beginner', title: 'Best Times' }, { adapter })
+
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalled())
+    const q = adapter.listScores.mock.calls[0][0]
+    expect(q.category).toBe('beginner')
+    expect(q.order).toBe('asc')
+    expect(q.limit).toBe(10)
+    expect(q.since).toBeInstanceOf(Date)
+    const dayMs = 24 * 60 * 60 * 1000
+    expect(Math.abs(Date.now() - dayMs - q.since.getTime())).toBeLessThan(5000)
+  })
+
+  it('honors the duration attribute on first mount (all → no time filter)', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'Best', duration: 'all' }, { adapter })
+
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalled())
+    expect(adapter.listScores.mock.calls[0][0].since).toBeNull()
+    await vi.waitFor(() =>
+      expect(tabByLabel(el, 'All Time').style.fontWeight).toBe('bold'))
+  })
+
+  it('passes score-order=\'desc\' through to the query', async () => {
+    const adapter = makeAdapter([])
+    mount({ category: 'beginner', title: 'Best', 'score-order': 'desc' }, { adapter })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalled())
+    expect(adapter.listScores.mock.calls[0][0].order).toBe('desc')
+  })
+
+  it('re-queries the clicked tab window in place', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'Best' }, { adapter })
+    await vi.waitFor(() => expect(tabButtons(el)).toHaveLength(4))
+
+    tabByLabel(el, 'Week').click()
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+    const q = adapter.listScores.mock.calls[1][0]
+    const weekMs = 7 * 24 * 60 * 60 * 1000
+    expect(Math.abs(Date.now() - weekMs - q.since.getTime())).toBeLessThan(5000)
+    await vi.waitFor(() =>
+      expect(tabByLabel(el, 'Week').style.fontWeight).toBe('bold'))
+    expect(tabByLabel(el, 'Today').style.fontWeight).toBe('normal')
+  })
+
+  it('keeps focus on the clicked tab', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'Best' }, { adapter })
+    await vi.waitFor(() => expect(tabButtons(el)).toHaveLength(4))
+
+    const week = tabByLabel(el, 'Week')
+    week.focus()
+    week.click()
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+    expect(document.activeElement?.textContent).toBe('Week')
+  })
+})
+
+describe('attribute changes after mount', () => {
+  it('category change re-queries with the new category and keeps the selected tab', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'Best' }, { adapter })
+    await vi.waitFor(() => expect(tabButtons(el)).toHaveLength(4))
+
+    tabByLabel(el, 'Week').click()
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+
+    el.setAttribute('category', 'expert')
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(3))
+    const q = adapter.listScores.mock.calls[2][0]
+    expect(q.category).toBe('expert')
+    const weekMs = 7 * 24 * 60 * 60 * 1000
+    expect(Math.abs(Date.now() - weekMs - q.since.getTime())).toBeLessThan(5000)
+    await vi.waitFor(() =>
+      expect(tabByLabel(el, 'Week').style.fontWeight).toBe('bold'))
+  })
+
+  it('title change updates the heading', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'Best' }, { adapter })
+    await vi.waitFor(() => expect(el.querySelector('h3')).toBeTruthy())
+
+    el.setAttribute('title', 'Best Times (Expert)')
+    await vi.waitFor(() =>
+      expect(el.querySelector('h3').textContent).toBe('Best Times (Expert)'))
+  })
+
+  it('duration change switches the window', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'Best' }, { adapter })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(1))
+
+    el.setAttribute('duration', 'month')
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+    const q = adapter.listScores.mock.calls[1][0]
+    const monthMs = 30 * 24 * 60 * 60 * 1000
+    expect(Math.abs(Date.now() - monthMs - q.since.getTime())).toBeLessThan(5000)
+    await vi.waitFor(() =>
+      expect(tabByLabel(el, 'Month').style.fontWeight).toBe('bold'))
+  })
+
+  it('a stale query result never overwrites a newer one', async () => {
+    const deferred = {}
+    const adapter = makeAdapter([], {
+      listScores: vi.fn(({ category }) => new Promise(r => { deferred[category] = r }))
+    })
+    const el = mount({ category: 'aaa', title: 'Best' }, { adapter })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(1))
+
+    el.setAttribute('category', 'bbb')
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+
+    deferred.bbb([{ name: 'NewRow', score: 2 }])
+    await vi.waitFor(() => expect(rowsText(el)).toContain('NewRow'))
+
+    deferred.aaa([{ name: 'StaleRow', score: 1 }]) // stale response arrives late
+    await new Promise(r => setTimeout(r, 20))
+    expect(rowsText(el)).not.toContain('StaleRow')
+    expect(rowsText(el)).toContain('NewRow')
+  })
+})
+
+describe('empty and error states', () => {
+  it('shows one of the empty-state messages when there are no rows', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'Best' }, { adapter })
+    await vi.waitFor(() => {
+      const messages = [...el.querySelectorAll('em')].map(em => em.textContent)
+      expect(messages.some(m => DEFAULT_EMPTY_MESSAGES.includes(m))).toBe(true)
+    })
+  })
+
+  it('turns a failing query into the error message', async () => {
+    const adapter = makeAdapter([], {
+      listScores: vi.fn(async () => { throw new Error('backend down') })
+    })
+    const el = mount({ category: 'beginner', title: 'Best' }, { adapter })
+    await vi.waitFor(() =>
+      expect(rowsText(el)).toContain('Leaderboard unavailable right now.'))
+    expect(el.querySelector('h3')).toBeTruthy() // heading + tabs survive the failure
+  })
+})
+
+describe('formatting and user-facing strings', () => {
+  it('format=\'time\' renders scores with the pretty-time formatter', async () => {
+    const adapter = makeAdapter([
+      { name: 'Ada', score: 4200 },
+      { name: 'Bo', score: 61300 }
+    ])
+    const el = mount({ category: 'b', title: 'T', format: 'time' }, { adapter })
+    await vi.waitFor(() => {
+      expect(rowsText(el)).toContain('04.2')
+      expect(rowsText(el)).toContain('01:01.3')
+    })
+  })
+
+  it('a per-element formatScore property wins over the format attribute', async () => {
+    const adapter = makeAdapter([{ name: 'Ada', score: 4200 }])
+    const el = mount(
+      { category: 'b', title: 'T', format: 'time' },
+      { adapter, formatScore: v => `${v}pts` }
+    )
+    await vi.waitFor(() => expect(rowsText(el)).toContain('4200pts'))
+  })
+
+  it('falls back to shared-config format from configureLeaderboard()', async () => {
+    const adapter = makeAdapter([{ name: 'Ada', score: 4200 }])
+    configureLeaderboard({ adapter, format: 'time' })
+    const el = mount({ category: 'b', title: 'T' })
+    await vi.waitFor(() => expect(rowsText(el)).toContain('04.2'))
+  })
+
+  it('honors per-element string overrides (loadingText, errorText, anonymousName)', async () => {
+    let reject
+    const adapter = makeAdapter([], {
+      listScores: vi.fn(() => new Promise((_, rj) => { reject = rj }))
+    })
+    const el = mount({ category: 'b', title: 'T' }, {
+      adapter,
+      loadingText: 'Hold on…',
+      errorText: 'Nope.',
+      anonymousName: 'Mystery Player'
+    })
+    await vi.waitFor(() => expect(rowsText(el)).toContain('Hold on…'))
+    reject(new Error('x'))
+    await vi.waitFor(() => expect(rowsText(el)).toContain('Nope.'))
+  })
+
+  it('uses the anonymous name for rows without a name', async () => {
+    const adapter = makeAdapter([{ score: 9 }])
+    const el = mount({ category: 'b', title: 'T' }, { adapter, anonymousName: 'Mystery' })
+    await vi.waitFor(() => expect(rowsText(el)).toContain('Mystery'))
+  })
+
+  it('honors shared-config labels, tooltips and emptyMessages', async () => {
+    const adapter = makeAdapter([])
+    configureLeaderboard({
+      adapter,
+      labels: { today: 'Heute' },
+      tooltips: { today: 'Letzte 24 Stunden' },
+      emptyMessages: ['Nichts hier.']
+    })
+    const el = mount({ category: 'b', title: 'T' })
+    await vi.waitFor(() => {
+      const tab = tabByLabel(el, 'Heute')
+      expect(tab).toBeTruthy()
+      expect(tab.getAttribute('title')).toBe('Letzte 24 Stunden')
+      expect(rowsText(el)).toContain('Nichts hier.')
+    })
+  })
+})
+
+describe('submit()', () => {
+  const entry = () => ({
+    name: 'Zed',
+    playerId: 'p1',
+    score: 42,
+    category: 'beginner',
+    time_stamp: new Date('2026-07-03T12:00:00Z'),
+    status: 'win',
+    meta: { isMobile: false }
+  })
+
+  it('archives and writes a ranked entry with bucket keys', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'T' }, { adapter })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalled())
+
+    await el.submit(entry())
+
+    expect(adapter.archive).toHaveBeenCalledWith({
+      playerId: 'p1',
+      score: 42,
+      category: 'beginner',
+      time_stamp: entry().time_stamp,
+      meta: { isMobile: false }
+    })
+    expect(adapter.addScore).toHaveBeenCalledTimes(1)
+    const [category, doc] = adapter.addScore.mock.calls[0]
+    expect(category).toBe('beginner')
+    expect(doc).toMatchObject({
+      name: 'Zed',
+      playerId: 'p1',
+      score: 42,
+      day: '2026-07-03',
+      week: '2026-W27',
+      month: '2026-07'
+    })
+  })
+
+  it('skips the ranked write when the entry does not qualify', async () => {
+    const adapter = makeAdapter([], {
+      getConfig: vi.fn(async () => ({ passingStatus: 'win' }))
+    })
+    const el = mount({ category: 'beginner', title: 'T' }, { adapter })
+    await vi.waitFor(() => expect(adapter.getConfig).toHaveBeenCalled())
+    await new Promise(r => setTimeout(r, 0)) // let the writer store the config
+
+    await el.submit({ ...entry(), status: 'lose' })
+    expect(adapter.archive).toHaveBeenCalledTimes(1)
+    expect(adapter.addScore).not.toHaveBeenCalled()
+  })
+
+  it('honors a per-element qualifies override', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'beginner', title: 'T' }, {
+      adapter,
+      qualifies: () => false
+    })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalled())
+
+    await el.submit(entry())
+    expect(adapter.addScore).not.toHaveBeenCalled()
+  })
+
+  it('is a safe no-op on an unconfigured element', async () => {
+    const el = mount({ category: 'beginner', title: 'T' })
+    await vi.waitFor(() => expect(rowsText(el)).toContain('Leaderboard not configured.'))
+    expect(el.submit(entry())).toBeUndefined()
+  })
+})
+
+describe('regressions pinned after review', () => {
+  it('renders entry names as text, never as HTML (element path)', async () => {
+    const adapter = makeAdapter([{ name: '<img src=x onerror=alert(1)>', score: 1 }])
+    const el = mount({ category: 'b', title: 'T' }, { adapter })
+    await vi.waitFor(() => expect(rowsText(el)).toContain('<img src=x onerror=alert(1)>'))
+    expect(el.querySelector('img')).toBeNull()
+  })
+
+  it('an invalid duration id shows the error text without querying the adapter', async () => {
+    const adapter = makeAdapter([{ name: 'Ada', score: 1 }])
+    const el = mount({ category: 'b', title: 'T', duration: 'yesterday' }, { adapter })
+    await vi.waitFor(() =>
+      expect(rowsText(el)).toContain('Leaderboard unavailable right now.'))
+    expect(adapter.listScores).not.toHaveBeenCalled()
+  })
+
+  it('a title change does not re-query the backend', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'b', title: 'T' }, { adapter })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(1))
+
+    el.setAttribute('title', 'New Title')
+    await vi.waitFor(() => expect(el.querySelector('h3').textContent).toBe('New Title'))
+    expect(adapter.listScores).toHaveBeenCalledTimes(1)
+  })
+
+  it('a score-order change after mount takes effect on the next query', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'b', title: 'T', 'score-order': 'asc' }, { adapter })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(1))
+    expect(adapter.listScores.mock.calls[0][0].order).toBe('asc')
+
+    el.setAttribute('score-order', 'desc')
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+    expect(adapter.listScores.mock.calls[1][0].order).toBe('desc')
+  })
+
+  it('a format change after mount takes effect on the next render', async () => {
+    const adapter = makeAdapter([{ name: 'Ada', score: 4200 }])
+    const el = mount({ category: 'b', title: 'T' }, { adapter })
+    await vi.waitFor(() => expect(rowsText(el)).toContain('4200'))
+
+    el.setAttribute('format', 'time')
+    await vi.waitFor(() => expect(rowsText(el)).toContain('04.2'))
+  })
+
+  it('a score-order change while detached takes effect on re-connect', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'b', title: 'T', 'score-order': 'asc' }, { adapter })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(1))
+
+    el.remove()
+    el.setAttribute('score-order', 'desc')
+    document.body.append(el)
+    await vi.waitFor(() => {
+      const calls = adapter.listScores.mock.calls
+      expect(calls[calls.length - 1][0].order).toBe('desc')
+    })
+  })
+
+  it('configureLeaderboard() re-mounts every live element, keeping each selected tab', async () => {
+    const adapter = makeAdapter([])
+    configureLeaderboard({ adapter })
+    const one = mount({ category: 'a', title: 'One' })
+    const two = mount({ category: 'b', title: 'Two' })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+
+    tabByLabel(two, 'Week').click()
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(3))
+
+    // Re-configuring re-mounts BOTH live elements (string overrides won't
+    // apply to their already-cached services — pinned separately below).
+    configureLeaderboard({})
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(5))
+    // element two kept its Week selection through the shared re-mount
+    await vi.waitFor(() => {
+      expect(tabByLabel(two, 'Week').style.fontWeight).toBe('bold')
+      expect(tabByLabel(one, 'Today').style.fontWeight).toBe('bold')
+    })
+  })
+
+  it('a detached element is not re-mounted by configureLeaderboard, but remembers its tab on re-connect', async () => {
+    const adapter = makeAdapter([])
+    const el = mount({ category: 'b', title: 'T' }, { adapter })
+    await vi.waitFor(() => expect(tabButtons(el)).toHaveLength(4))
+    tabByLabel(el, 'Month').click()
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+
+    el.remove()
+    const callsWhileDetached = adapter.listScores.mock.calls.length
+    configureLeaderboard({ loadingText: 'Wait…' })
+    expect(adapter.listScores.mock.calls.length).toBe(callsWhileDetached)
+
+    document.body.append(el)
+    await vi.waitFor(() =>
+      expect(tabByLabel(el, 'Month').style.fontWeight).toBe('bold'))
+  })
+
+  it('keeps the cached service (old adapter) when configureLeaderboard swaps adapters later', async () => {
+    const first = makeAdapter([])
+    configureLeaderboard({ adapter: first })
+    mount({ category: 'b', title: 'T' })
+    await vi.waitFor(() => expect(first.listScores).toHaveBeenCalledTimes(1))
+
+    const second = makeAdapter([])
+    configureLeaderboard({ adapter: second })
+    await vi.waitFor(() => expect(first.listScores).toHaveBeenCalledTimes(2))
+    expect(second.listScores).not.toHaveBeenCalled() // documented caching semantics
+  })
+
+  it('keeps the cached service (old strings) when configureLeaderboard changes strings later', async () => {
+    const adapter = makeAdapter([])
+    configureLeaderboard({ adapter })
+    const el = mount({ category: 'b', title: 'T' })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(1))
+
+    configureLeaderboard({ emptyMessages: ['Nothing here yet.'] })
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+    // the already-built service keeps its original strings (documented caching)
+    expect(rowsText(el)).not.toContain('Nothing here yet.')
+  })
+
+  it('keeps focus on a clicked tab when composed inside a shadow root', async () => {
+    const adapter = makeAdapter([])
+    const host = document.createElement('div')
+    const shadow = host.attachShadow({ mode: 'open' })
+    const el = /** @type {any} */ (document.createElement('cozy-leaderboard'))
+    el.setAttribute('category', 'b')
+    el.setAttribute('title', 'T')
+    el.adapter = adapter
+    shadow.append(el)
+    document.body.append(host)
+    await vi.waitFor(() => expect(el.querySelectorAll('button')).toHaveLength(4))
+
+    const week = [...el.querySelectorAll('button')].find(b => b.textContent === 'Week')
+    week.focus()
+    week.click()
+    await vi.waitFor(() => expect(adapter.listScores).toHaveBeenCalledTimes(2))
+    expect(shadow.activeElement?.textContent).toBe('Week')
+  })
+
+  it('pins prettyTime edge cases through the format attribute', async () => {
+    const adapter = makeAdapter([
+      { name: 'Zero', score: 0 },
+      { name: 'Minute', score: 60000 }
+    ])
+    const el = mount({ category: 'b', title: 'T', format: 'time' }, { adapter })
+    await vi.waitFor(() => {
+      expect(rowsText(el)).toContain('Zero')
+      expect(rowsText(el)).toContain('0') // falsy score -> '0'
+      expect(rowsText(el)).toContain('01:0') // exact minute -> '01:0'
+    })
+  })
+})

packages/leaderboard/test/read-write-separation.test.js

@@ -0,0 +1,123 @@
+// @ts-check
+import { describe, it, expect, vi } from 'vitest'
+import { readFileSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { dirname, join } from 'node:path'
+
+import { LeaderBoardReader } from '../leaderboard-read.js'
+import { LeaderBoardWriter } from '../leaderboard-write.js'
+import { LeaderBoardService } from '../leader-board.js'
+
+const pkgDir = join(dirname(fileURLToPath(import.meta.url)), '..')
+const source = (file) => readFileSync(join(pkgDir, file), 'utf8')
+  .replace(/\/\*[\s\S]*?\*\//g, '') // strip block comments
+  .replace(/\/\/.*$/gm, '')          // strip line comments
+
+describe('read/write surface separation — imports', () => {
+  it('the READ module pulls in no write-path code', () => {
+    const code = source('leaderboard-read.js')
+    // no import of the write module or its unique dependency (bucket keys)
+    expect(code).not.toMatch(/from\s+['"][^'"]*leaderboard-write/)
+    expect(code).not.toMatch(/date-bucket|buckets/)
+    // no write operations
+    expect(code).not.toMatch(/\bsubmit\b|\baddScore\b|\barchive\b/)
+  })
+
+  it('the WRITE module pulls in no read/render code', () => {
+    const code = source('leaderboard-write.js')
+    expect(code).not.toMatch(/from\s+['"][^'"]*leaderboard-read/)
+    // no DOM / rendering / listing
+    expect(code).not.toMatch(/\bdocument\b|\brender\b|\blistScores\b|createElement/)
+  })
+})
+
+describe('read surface — usable standalone (no writes)', () => {
+  it('renders a ranked list via listScores and never calls write methods', async () => {
+    const listScores = vi.fn(async () => [{ name: 'Ada', score: 10 }, { name: 'Bo', score: 20 }])
+    // A deliberately read-only adapter: no addScore/archive at all.
+    const adapter = { listScores }
+    const reader = new LeaderBoardReader({ adapter, scoreOrder: 'asc', formatScore: String })
+
+    const el = await reader.render('beginner', 'Best Times')
+    expect(el.querySelector('h3')).toBeTruthy()          // heading rendered
+    expect(el.querySelectorAll('button')).toHaveLength(4) // four duration tabs
+    expect(listScores).toHaveBeenCalledTimes(1)           // 'today' window loaded once
+
+    // The list fills asynchronously — wait for the rows to appear (names render as text).
+    await vi.waitFor(() => {
+      expect(el.textContent).toContain('Ada')
+      expect(el.textContent).toContain('Bo')
+    })
+
+    // Reader exposes no write API.
+    expect(typeof (/** @type {any} */ (reader).submit)).toBe('undefined')
+  })
+
+  it('renders entry names as text, never as HTML (names are player-controlled)', async () => {
+    const listScores = vi.fn(async () => [{ name: '<img src=x onerror=alert(1)>', score: 1 }])
+    const reader = new LeaderBoardReader({ adapter: { listScores } })
+
+    const el = await reader.render('beginner', 'Best Times')
+    await vi.waitFor(() =>
+      expect(el.textContent).toContain('<img src=x onerror=alert(1)>'))
+    expect(el.querySelector('img')).toBeNull()
+  })
+})
+
+describe('write surface — usable standalone with an injected instance', () => {
+  it('submits a completed game through the injected adapter (archive + ranked write)', async () => {
+    const archive = vi.fn(async () => {})
+    const addScore = vi.fn(async () => {})
+    // Injected, write-capable adapter (no listScores/render needed).
+    const adapter = { archive, addScore }
+    const writer = new LeaderBoardWriter({ adapter })
+
+    await writer.submit({
+      name: 'Ada', playerId: 'p1', score: 42, category: 'beginner', time_stamp: Date.UTC(2026, 6, 3)
+    })
+
+    expect(archive).toHaveBeenCalledTimes(1)
+    expect(addScore).toHaveBeenCalledTimes(1)
+    const [category, doc] = addScore.mock.calls[0]
+    expect(category).toBe('beginner')
+    expect(doc).toMatchObject({ name: 'Ada', playerId: 'p1', score: 42 })
+    // denormalized bucket keys are computed on the write side
+    expect(doc).toEqual(expect.objectContaining({ day: expect.any(String), week: expect.any(String), month: expect.any(String) }))
+
+    // Writer exposes no read/render API.
+    expect(typeof (/** @type {any} */ (writer).render)).toBe('undefined')
+  })
+
+  it('honors an explicit qualifies gate (skips the ranked write, still archives)', async () => {
+    const archive = vi.fn(async () => {})
+    const addScore = vi.fn(async () => {})
+    const writer = new LeaderBoardWriter({ adapter: { archive, addScore }, qualifies: () => false })
+    await writer.submit({ playerId: 'p1', score: 1, category: 'beginner', time_stamp: 0 })
+    expect(archive).toHaveBeenCalledTimes(1)
+    expect(addScore).not.toHaveBeenCalled()
+  })
+})
+
+describe('facade — combined surface unchanged (regression)', () => {
+  it('LeaderBoardService delegates render (read) and submit (write)', async () => {
+    const listScores = vi.fn(async () => [{ name: 'Ada', score: 10 }])
+    const archive = vi.fn(async () => {})
+    const addScore = vi.fn(async () => {})
+    const adapter = { listScores, archive, addScore }
+    const service = new LeaderBoardService({ adapter, formatScore: String })
+
+    // read
+    const el = await service.render('beginner', 'Best')
+    expect(el.querySelector('h3')).toBeTruthy()
+    expect(listScores).toHaveBeenCalled()
+    await vi.waitFor(() => expect(el.textContent).toContain('Ada'))
+
+    // write
+    await service.submit({ name: 'Ada', playerId: 'p1', score: 5, category: 'beginner', time_stamp: 0 })
+    expect(addScore).toHaveBeenCalledTimes(1)
+
+    // composed surfaces are reachable
+    expect(service.reader).toBeInstanceOf(LeaderBoardReader)
+    expect(service.writer).toBeInstanceOf(LeaderBoardWriter)
+  })
+})

packages/leaderboard/test/supabase-adapter.test.js

@@ -0,0 +1,48 @@
+// @ts-check
+import { describe, it, expect, vi } from 'vitest'
+import { SupabaseAdapter } from '../adapters/supabase.js'
+
+// A chainable stand-in for a supabase-js client (consumer-constructed — the
+// package takes no supabase dependency). A privileged/service-role client is
+// supplied the same way.
+function mockClient() {
+  const insert = vi.fn(async () => ({ error: null }))
+  const from = vi.fn(() => ({ insert }))
+  return { from, insert }
+}
+
+describe('SupabaseAdapter — consumer-supplied client (injection point exists)', () => {
+  it('uses the injected client as-is', () => {
+    const client = mockClient()
+    const adapter = new SupabaseAdapter({ client, namespace: 'mw' })
+    expect(adapter.client).toBe(client)
+  })
+
+  it('performs a write through the injected client', async () => {
+    const client = mockClient()
+    const adapter = new SupabaseAdapter({ client, namespace: 'mw' })
+
+    await adapter.addScore('beginner', {
+      name: 'A', playerId: 'p1', score: 5, category: 'beginner', time_stamp: 't'
+    })
+
+    expect(client.from).toHaveBeenCalledWith('mw_scores')
+    expect(client.insert).toHaveBeenCalledTimes(1)
+    expect(client.insert.mock.calls[0][0]).toMatchObject({ name: 'A', player_id: 'p1', score: 5 })
+  })
+
+  it('archives through the injected client', async () => {
+    const client = mockClient()
+    const adapter = new SupabaseAdapter({ client, namespace: 'mw' })
+    await adapter.archive({ playerId: 'p1', score: 9, category: 'beginner', time_stamp: 't' })
+    expect(client.from).toHaveBeenCalledWith('mw_archive')
+    expect(client.insert.mock.calls[0][0]).toMatchObject({ player_id: 'p1', score: 9 })
+  })
+
+  it('surfaces backend errors from the injected client', async () => {
+    const insert = vi.fn(async () => ({ error: new Error('permission denied') }))
+    const client = { from: vi.fn(() => ({ insert })) }
+    const adapter = new SupabaseAdapter({ client, namespace: 'mw' })
+    await expect(adapter.addScore('beginner', { playerId: 'p' })).rejects.toThrow('permission denied')
+  })
+})

packages/mnswpr/TUTORIAL.md

@@ -61,7 +61,7 @@ npm i -D vite
 Now that the JS project is initialized and we have a development environment with `vite`, we will install **mnswpr** as a dependency:
 
 ```bash
-npm i @ayo-run/mnswpr
+npm i @cozy-games/mnswpr
 ```
 
 Finally, you can run the installed `vite` dev server by running the following:
@@ -141,8 +141,8 @@ Create a new file named `main.js` with the following content:
 /**
  * main.js
  */
-import '@ayo-run/mnswpr/mnswpr.css'
+import '@cozy-games/mnswpr/mnswpr.css'
-import mnswpr from '@ayo-run/mnswpr'
+import mnswpr from '@cozy-games/mnswpr'
 
 const game = new mnswpr('app')
 game.initialize()

packages/mnswpr/adapters/replay-common.js

@@ -0,0 +1,24 @@
+// @ts-check
+
+/**
+ * @typedef {import('../core/minesweeper/rules.js').MoveEvent} MnswprMoveEvent
+ */
+
+/**
+ * Map a recorded move-event back to the rules move that produced it: `flag` and
+ * `unflag` are both the toggle move `flag`; `reveal` and `chord` pass through.
+ * Unknown kinds are ignored. Shared by the mnswpr replay adapters (progress and
+ * full-board state) so both replay a stream through the core rules identically.
+ *
+ * @param {MnswprMoveEvent} e
+ * @returns {{ type: 'reveal' | 'flag' | 'chord', r: number, c: number } | null}
+ */
+export function toMove(e) {
+  switch (e && e.type) {
+    case 'reveal': return { type: 'reveal', r: e.r, c: e.c }
+    case 'chord': return { type: 'chord', r: e.r, c: e.c }
+    case 'flag':
+    case 'unflag': return { type: 'flag', r: e.r, c: e.c }
+    default: return null
+  }
+}

packages/mnswpr/adapters/replay-progress.js

@@ -0,0 +1,40 @@
+// @ts-check
+import { MinesweeperRules } from '../core/minesweeper/rules.js'
+import { toMove } from './replay-common.js'
+
+/**
+ * @typedef {import('../core/minesweeper/rules.js').MoveEvent} MnswprMoveEvent
+ * @typedef {import('../core/minesweeper/board.js').Layout} Layout
+ */
+
+/**
+ * The percent-cleared progress reducer for Minesweeper — mnswpr's first concrete
+ * implementation of the replay engine's `ProgressReducer<MnswprMoveEvent>` seam
+ * (see `@cozy-games/replay` / replay-02). Given the ordered slice of move-events
+ * played so far, it returns completion as
+ * `revealed safe cells / total safe cells * 100`.
+ *
+ * Why it needs the board: a single `reveal` or `chord` event floods MANY cells,
+ * but the recorded move-event only carries `{ type, r, c }` — not how many cells
+ * opened. So the reducer takes the board as closure input (consistent with the
+ * interface design) and replays the moves through the pure core rules. That makes
+ * reveals flood, chords reveal via their (non-flagged) neighbors, and
+ * flags/unflags only gate chords — never advancing progress themselves — with no
+ * cell double-counted. The engine stays game-blind; all interpretation is here.
+ *
+ * @param {Layout} layout - the recorded board (as produced by `generateBoard`)
+ * @returns {(events: { event: MnswprMoveEvent }[]) => number} a reducer to `[0, 100]`
+ */
+export function createProgressReducer(layout) {
+  const totalSafe = layout.rows * layout.cols - layout.mines
+  return function progress(events) {
+    // A board with no safe cells is vacuously fully cleared (and avoids /0).
+    if (totalSafe === 0) return 100
+    let state = MinesweeperRules.fromLayout(layout)
+    for (const record of events) {
+      const move = toMove(record.event)
+      if (move) state = MinesweeperRules.apply(state, move).state
+    }
+    return (state.revealedSafe / totalSafe) * 100
+  }
+}

packages/mnswpr/adapters/replay-state.js

@@ -0,0 +1,57 @@
+// @ts-check
+import { MinesweeperRules } from '../core/minesweeper/rules.js'
+import { toMove } from './replay-common.js'
+
+/**
+ * @typedef {import('../core/minesweeper/rules.js').MoveEvent} MnswprMoveEvent
+ * @typedef {import('../core/minesweeper/board.js').Layout} Layout
+ * @typedef {{ mine: boolean, adjacent: number, status: 'hidden' | 'flagged' | 'revealed' }} BoardCell
+ * @typedef {{ rows: number, cols: number, phase: string, revealedSafe: number, cells: BoardCell[][] }} BoardState
+ */
+
+/**
+ * The full-board state reducer for Minesweeper — mnswpr's implementation of the
+ * replay engine's `StateReducer<MnswprMoveEvent, BoardState>` seam (replay-05).
+ * Given the ordered slice of move-events played so far, it reconstructs the
+ * COMPLETE board at that point: every cell's mine/adjacent/status plus the phase.
+ *
+ * Like the progress reducer, it takes the board as closure input and replays the
+ * moves through the pure core rules — so reveals flood, chords open their
+ * neighbors, and flags toggle — giving an exact reconstruction at any event
+ * index. Statelessly a function of the slice, so the engine can jump (seek) to
+ * any position and rebuild the board there.
+ *
+ * @param {Layout} layout - the recorded board (as produced by `generateBoard`)
+ * @returns {(events: { event: MnswprMoveEvent }[]) => BoardState}
+ */
+export function createStateReducer(layout) {
+  return function state(events) {
+    let s = MinesweeperRules.fromLayout(layout)
+    for (const record of events) {
+      const move = toMove(record.event)
+      if (move) s = MinesweeperRules.apply(s, move).state
+    }
+    return toBoard(s)
+  }
+}
+
+/**
+ * Project a core game state into a plain, render-ready 2D board snapshot.
+ * @param {import('../core/minesweeper/rules.js').State} s
+ * @returns {BoardState}
+ */
+function toBoard(s) {
+  const { rows, cols } = s.config
+  /** @type {BoardCell[][]} */
+  const cells = []
+  for (let r = 0; r < rows; r++) {
+    /** @type {BoardCell[]} */
+    const row = []
+    for (let c = 0; c < cols; c++) {
+      const cell = s.grid.at(r, c)
+      row.push({ mine: cell.mine, adjacent: cell.adjacent, status: cell.status })
+    }
+    cells.push(row)
+  }
+  return { rows, cols, phase: s.phase, revealedSafe: s.revealedSafe, cells }
+}

packages/mnswpr/client/renderer.js

@@ -0,0 +1,114 @@
+// @ts-check
+
+/**
+ * The renderer — the ONLY place the client touches game DOM. It consumes core
+ * events + the projected view and reproduces the exact attributes/classes the
+ * game has always used (`data-status`, `data-value`, class names), so existing
+ * CSS and the jsdom tests are unaffected. It reads nothing from the core beyond
+ * the projected view, so board secrecy stays a drop-in later (invariant #3).
+ */
+
+function cellAt(grid, r, c) {
+  return grid.rows[r].cells[c]
+}
+
+/** Reveal a safe cell — matches the old revealSafeCell() DOM exactly. */
+function renderRevealed(grid, r, c, adjacent) {
+  const cell = cellAt(grid, r, c)
+  cell.className = 'clicked'
+  cell.setAttribute('data-status', 'clicked')
+  const span = document.createElement('span')
+  if (adjacent === 0) {
+    span.innerHTML = ' '
+    cell.innerHTML = ''
+    cell.appendChild(span)
+    cell.setAttribute('data-status', 'empty')
+  } else {
+    span.innerHTML = String(adjacent)
+    cell.innerHTML = ''
+    cell.appendChild(span)
+    cell.setAttribute('data-value', String(adjacent))
+  }
+}
+
+/** Toggle a flag — matches the old rightClickCell() DOM. */
+function renderFlag(grid, r, c, flagged) {
+  const cell = cellAt(grid, r, c)
+  if (flagged) {
+    cell.className = 'flag'
+    cell.setAttribute('data-status', 'flagged')
+  } else {
+    cell.className = ''
+    cell.setAttribute('data-status', 'default')
+  }
+}
+
+/** @returns {Set<string>} "r,c" keys of every mine in the terminal view */
+function mineSet(view) {
+  const set = new Set()
+  for (const cell of view.cells) {
+    if (cell.mine) set.add(`${cell.r},${cell.c}`)
+  }
+  return set
+}
+
+/**
+ * Apply per-move events to the grid (reveal / flag / the clicked mine on
+ * explode). Terminal board reveal is handled separately by revealBoard().
+ * @param {HTMLTableElement} grid
+ * @param {object[]} events
+ */
+export function renderEvents(grid, events) {
+  for (const ev of events) {
+    if (ev.type === 'reveal') {
+      for (const c of ev.cells) renderRevealed(grid, c.r, c.c, c.adjacent)
+    } else if (ev.type === 'flag') {
+      renderFlag(grid, ev.r, ev.c, ev.flagged)
+    } else if (ev.type === 'explode') {
+      const cell = cellAt(grid, ev.r, ev.c)
+      cell.className = 'clicked'
+      cell.setAttribute('data-status', 'clicked')
+    }
+  }
+}
+
+/**
+ * Reveal the whole board at game end, reproducing the old handleWinRevelation /
+ * handleLostRevelation output. On a win, mines are marked correct; on a loss,
+ * unflagged mines detonate and wrong flags are marked.
+ * @param {HTMLTableElement} grid
+ * @param {{ phase: string, cells: object[] }} view
+ * @param {{ rows: number, cols: number }} setting
+ */
+export function revealBoard(grid, view, setting) {
+  const won = view.phase === 'won'
+  const mines = mineSet(view)
+  for (let r = 0; r < setting.rows; r++) {
+    for (let c = 0; c < setting.cols; c++) {
+      const cell = cellAt(grid, r, c)
+      const isMine = mines.has(`${r},${c}`)
+      const isFlagged = cell.getAttribute('data-status') === 'flagged'
+      if (won) {
+        if (isMine) {
+          cell.innerHTML = ':)'
+          cell.className = 'correct'
+          cell.setAttribute('data-status', 'clicked')
+          cell.setAttribute('title', 'Correct')
+        }
+      } else if (isFlagged) {
+        if (isMine) {
+          cell.innerHTML = ':)'
+          cell.className = 'correct'
+          cell.setAttribute('title', 'Correct')
+        } else {
+          cell.innerHTML = 'X'
+          cell.className = 'wrong'
+          cell.setAttribute('title', 'Wrong')
+        }
+      } else if (isMine) {
+        cell.className = 'mine'
+        cell.setAttribute('data-status', 'clicked')
+      }
+    }
+  }
+}

packages/mnswpr/client/transport.js

@@ -0,0 +1,48 @@
+// @ts-check
+import { GameSession } from '../core/session/session.js'
+
+/**
+ * In-process transport: runs a `GameSession` locally and emits its events.
+ *
+ * The Transport interface is intentionally async — `send()` returns a Promise —
+ * so a future `RemoteTransport` (server-authoritative) is a drop-in with no
+ * change to the client (server-readiness invariant #1). Rendering is driven by
+ * `onEvent`, which Local fires synchronously inside `send()` and Remote would
+ * fire when the server replies; the client never depends on `send()`'s timing.
+ *
+ * Only serializable messages cross this boundary (moves in; events + a projected
+ * view out) — never the live session/state (invariant #2).
+ */
+export class LocalTransport {
+  /**
+   * @param {object} rules - a GameRules implementation (e.g. MinesweeperRules)
+   * @param {{ seed: number, config: object, clock?: () => number }} opts
+   */
+  constructor(rules, opts) {
+    this.session = new GameSession(rules, opts)
+    this._subs = []
+  }
+
+  /** @param {(payload: { events: object[], view: object, time: number }) => void} cb */
+  onEvent(cb) {
+    this._subs.push(cb)
+    return () => { this._subs = this._subs.filter(s => s !== cb) }
+  }
+
+  /**
+   * Apply a move and emit the resulting events/view. Returns a Promise for
+   * interface parity with a remote transport.
+   * @param {object} move
+   * @returns {Promise<{ events: object[], view: object, time: number }>}
+   */
+  send(move) {
+    const payload = this.session.applyMove(move)
+    for (const cb of this._subs) cb(payload)
+    return Promise.resolve(payload)
+  }
+
+  status() { return this.session.status() }
+  view() { return this.session.view() }
+  result() { return this.session.result() }
+  elapsed() { return this.session.elapsed() }
+}

packages/mnswpr/core/grid/grid.js

@@ -0,0 +1,62 @@
+// @ts-check
+
+/**
+ * Layer 0 — a dense 2D container of opaque cells. Knows nothing about game
+ * meaning (no "mine", no "reveal"). Future home: @cozy-games/grid.
+ *
+ * @template Cell
+ */
+export class Grid {
+  /**
+   * @param {number} rows
+   * @param {number} cols
+   * @param {(r: number, c: number) => Cell} [fill] - factory for each cell
+   */
+  constructor(rows, cols, fill) {
+    this.rows = rows
+    this.cols = cols
+    /** @type {Cell[]} */
+    this._cells = new Array(rows * cols)
+    if (fill) {
+      for (let r = 0; r < rows; r++) {
+        for (let c = 0; c < cols; c++) {
+          this._cells[r * cols + c] = fill(r, c)
+        }
+      }
+    }
+  }
+
+  /** @returns {boolean} */
+  inBounds(r, c) {
+    return r >= 0 && c >= 0 && r < this.rows && c < this.cols
+  }
+
+  /** @returns {Cell} */
+  at(r, c) {
+    return this._cells[r * this.cols + c]
+  }
+
+  set(r, c, cell) {
+    this._cells[r * this.cols + c] = cell
+  }
+
+  /** @param {(cell: Cell, r: number, c: number) => void} fn */
+  forEach(fn) {
+    for (let r = 0; r < this.rows; r++) {
+      for (let c = 0; c < this.cols; c++) {
+        fn(this.at(r, c), r, c)
+      }
+    }
+  }
+
+  /**
+   * @template Out
+   * @param {(cell: Cell, r: number, c: number) => Out} fn
+   * @returns {Grid<Out>}
+   */
+  map(fn) {
+    const out = new Grid(this.rows, this.cols)
+    this.forEach((cell, r, c) => out.set(r, c, fn(cell, r, c)))
+    return out
+  }
+}

packages/mnswpr/core/grid/neighbors.js

@@ -0,0 +1,44 @@
+// @ts-check
+
+/**
+ * Neighbor STRATEGIES — the extraction seam. A game injects the topology it
+ * wants; the grid layer never assumes one. Minesweeper uses `eightWay`; a future
+ * Sudoku would inject its row/col/box `peers`. Each returns in-bounds [r, c]
+ * coordinate pairs.
+ *
+ * @typedef {{ inBounds: (r: number, c: number) => boolean }} Boundable
+ */
+
+/**
+ * All 8 surrounding cells (orthogonal + diagonal).
+ * @param {Boundable} grid
+ * @returns {Array<[number, number]>}
+ */
+export function eightWay(grid, r, c) {
+  const out = []
+  for (let dr = -1; dr <= 1; dr++) {
+    for (let dc = -1; dc <= 1; dc++) {
+      if (dr === 0 && dc === 0) continue
+      const nr = r + dr
+      const nc = c + dc
+      if (grid.inBounds(nr, nc)) out.push([nr, nc])
+    }
+  }
+  return out
+}
+
+/**
+ * The 4 orthogonal cells (N/E/S/W).
+ * @param {Boundable} grid
+ * @returns {Array<[number, number]>}
+ */
+export function orthogonal(grid, r, c) {
+  const out = []
+  const deltas = [[-1, 0], [1, 0], [0, -1], [0, 1]]
+  for (const [dr, dc] of deltas) {
+    const nr = r + dr
+    const nc = c + dc
+    if (grid.inBounds(nr, nc)) out.push([nr, nc])
+  }
+  return out
+}

packages/mnswpr/core/grid/serialize.js

@@ -0,0 +1,33 @@
+// @ts-check
+import { Grid } from './grid.js'
+
+/**
+ * Plain-JSON serialization of a Grid. Used by the move log / server persistence
+ * (Layer 1) and by replay. Cells must themselves be JSON-serializable.
+ *
+ * @template Cell
+ * @param {Grid<Cell>} grid
+ * @returns {{ rows: number, cols: number, cells: Cell[] }}
+ */
+export function toJSON(grid) {
+  const cells = []
+  grid.forEach(cell => cells.push(cell))
+  return { rows: grid.rows, cols: grid.cols, cells }
+}
+
+/**
+ * @template Cell
+ * @param {{ rows: number, cols: number, cells: Cell[] }} data
+ * @param {(cell: Cell) => Cell} [reviveCell]
+ * @returns {Grid<Cell>}
+ */
+export function fromJSON(data, reviveCell) {
+  const grid = new Grid(data.rows, data.cols)
+  for (let r = 0; r < data.rows; r++) {
+    for (let c = 0; c < data.cols; c++) {
+      const cell = data.cells[r * data.cols + c]
+      grid.set(r, c, reviveCell ? reviveCell(cell) : cell)
+    }
+  }
+  return grid
+}

packages/mnswpr/core/index.js

@@ -0,0 +1,25 @@
+// @ts-check
+
+/**
+ * `@cozy-games/mnswpr/core` — the headless, isomorphic Minesweeper core. No DOM, no
+ * wall clock. Runs identically in a browser (offline play) or on a server
+ * (authoritative timing / replay verification). See
+ * docs/headless-core-and-client-design.md.
+ */
+
+// Layer 0 — generic grid (future @cozy-games/grid)
+export { Grid } from './grid/grid.js'
+export { eightWay, orthogonal } from './grid/neighbors.js'
+export { toJSON, fromJSON } from './grid/serialize.js'
+
+// Layer 1 — generic session & authority (future @cozy-games/game-session)
+export { GameSession } from './session/session.js'
+export { replay } from './session/replay.js'
+export { mulberry32, randInt } from './session/rng.js'
+
+// Layer 2 — Minesweeper rules & pure board generation
+export { MinesweeperRules, MOVE_EVENT_TYPES } from './minesweeper/rules.js'
+export { generateBoard, validateLayout } from './minesweeper/board.js'
+
+// Shared level presets (also consumed by the DOM client)
+export { levels } from '../levels.js'

packages/mnswpr/core/minesweeper/board.js

@@ -0,0 +1,212 @@
+// @ts-check
+import { Grid } from '../grid/grid.js'
+import { mulberry32, randInt } from '../session/rng.js'
+import { eightWay } from '../grid/neighbors.js'
+
+/**
+ * @typedef {{ rows: number, cols: number, mines: number, id?: string }} Config
+ * @typedef {{ mine: boolean, adjacent: number, status: 'hidden' | 'flagged' | 'revealed' }} Cell
+ * @typedef {{ mine: boolean, adjacent: number }} LayoutCell
+ * @typedef {{ rows: number, cols: number, mines: number, cells: LayoutCell[][], mineLocations: [number, number][] }} Layout
+ */
+
+/** Shared empty exclude set for generation without first-click safety. */
+const NO_EXCLUDE = new Set()
+
+/**
+ * The set of cells kept mine-free for first-click safety: the clicked cell, plus
+ * its 8 neighbors when the board has room for all mines outside that 3x3. Falls
+ * back to just the clicked cell on boards too dense to spare the neighborhood.
+ *
+ * @param {Config} config
+ * @returns {Set<number>} coordinate keys (r * cols + c)
+ */
+export function excludeAround(config, r, c) {
+  const { rows, cols, mines } = config
+  const set = new Set([r * cols + c])
+  const roomFor3x3 = rows * cols - 9 >= mines
+  if (roomFor3x3) {
+    for (let dr = -1; dr <= 1; dr++) {
+      for (let dc = -1; dc <= 1; dc++) {
+        const nr = r + dr
+        const nc = c + dc
+        if (nr >= 0 && nc >= 0 && nr < rows && nc < cols) set.add(nr * cols + nc)
+      }
+    }
+  }
+  return set
+}
+
+/**
+ * Deterministically place mines and compute adjacency counts, mutating the grid
+ * in place. Pure function of (seed, config, exclude) — same inputs, same board.
+ * Thin convenience wrapper over {@link fillMines} that builds the RNG from a seed.
+ *
+ * @param {number} seed
+ * @param {Config} config
+ * @param {Set<number>} exclude - coordinate keys never to mine (first-click safety)
+ * @param {import('../grid/grid.js').Grid<Cell>} grid
+ * @returns {Set<number>} the mined coordinate keys
+ */
+export function placeMines(seed, config, exclude, grid) {
+  return fillMines(mulberry32(seed), config, exclude, grid)
+}
+
+/**
+ * The injected-RNG seam under {@link placeMines}: place mines and compute
+ * adjacency counts, mutating the grid in place. Takes an rng function (any
+ * `() => [0, 1)`), so callers own determinism — same rng sequence, same board.
+ *
+ * @param {() => number} rng
+ * @param {Config} config
+ * @param {Set<number>} exclude - coordinate keys never to mine (first-click safety)
+ * @param {import('../grid/grid.js').Grid<Cell>} grid
+ * @returns {Set<number>} the mined coordinate keys
+ */
+export function fillMines(rng, config, exclude, grid) {
+  const { rows, cols, mines } = config
+  const placed = new Set()
+  while (placed.size < mines) {
+    const key = randInt(rng, rows) * cols + randInt(rng, cols)
+    if (placed.has(key) || exclude.has(key)) continue
+    placed.add(key)
+  }
+  grid.forEach((cell, r, c) => { cell.mine = placed.has(r * cols + c) })
+  grid.forEach((cell, r, c) => {
+    if (cell.mine) { cell.adjacent = 0; return }
+    let n = 0
+    for (const [nr, nc] of eightWay(grid, r, c)) {
+      if (grid.at(nr, nc).mine) n++
+    }
+    cell.adjacent = n
+  })
+  return placed
+}
+
+/**
+ * Assert a plain layout object (as produced by {@link generateBoard}) is
+ * well-formed before it's injected into a game: correct dimensions, cell shape,
+ * a mine count that matches its own cells, and in-bounds mine positions. Throws a
+ * clear error on the first problem so a malformed board can't silently corrupt
+ * win detection or adjacency. Returns the layout for convenient chaining.
+ *
+ * @param {unknown} layout
+ * @returns {Layout}
+ */
+export function validateLayout(layout) {
+  if (layout === null || typeof layout !== 'object') {
+    throw new TypeError(`validateLayout: expected a layout object (got ${layout === null ? 'null' : typeof layout})`)
+  }
+  const { rows, cols, mines, cells, mineLocations } = /** @type {any} */ (layout)
+  if (!Number.isInteger(rows) || !Number.isInteger(cols) || rows < 1 || cols < 1) {
+    throw new RangeError(`validateLayout: rows/cols must be positive integers (got ${rows}x${cols})`)
+  }
+  if (!Array.isArray(cells) || cells.length !== rows) {
+    throw new RangeError(`validateLayout: cells must have ${rows} rows (got ${Array.isArray(cells) ? cells.length : typeof cells})`)
+  }
+  let mineCount = 0
+  for (let r = 0; r < rows; r++) {
+    const row = cells[r]
+    if (!Array.isArray(row) || row.length !== cols) {
+      throw new RangeError(`validateLayout: row ${r} must have ${cols} cells (got ${Array.isArray(row) ? row.length : typeof row})`)
+    }
+    for (let c = 0; c < cols; c++) {
+      const cell = row[c]
+      if (cell === null || typeof cell !== 'object' || typeof cell.mine !== 'boolean' || !Number.isInteger(cell.adjacent)) {
+        throw new TypeError(`validateLayout: cell (${r},${c}) must be { mine: boolean, adjacent: integer }`)
+      }
+      if (cell.mine) mineCount++
+    }
+  }
+  if (!Number.isInteger(mines) || mines < 0 || mines > rows * cols) {
+    throw new RangeError(`validateLayout: mines must be an integer in [0, ${rows * cols}] (got ${mines})`)
+  }
+  if (mineCount !== mines) {
+    throw new RangeError(`validateLayout: mines (${mines}) disagrees with ${mineCount} mined cells`)
+  }
+  // mineLocations is optional, but if present it must agree with the grid — the
+  // "dimensions vs. mine positions" cross-check.
+  if (mineLocations !== undefined) {
+    if (!Array.isArray(mineLocations) || mineLocations.length !== mineCount) {
+      throw new RangeError(`validateLayout: mineLocations must list all ${mineCount} mines (got ${Array.isArray(mineLocations) ? mineLocations.length : typeof mineLocations})`)
+    }
+    for (const loc of mineLocations) {
+      if (!Array.isArray(loc) || loc.length !== 2) {
+        throw new TypeError(`validateLayout: each mineLocation must be a [r, c] pair (got ${JSON.stringify(loc)})`)
+      }
+      const [r, c] = loc
+      if (!Number.isInteger(r) || !Number.isInteger(c) || r < 0 || c < 0 || r >= rows || c >= cols || !cells[r][c].mine) {
+        throw new RangeError(`validateLayout: mineLocation [${r}, ${c}] is out of bounds or not a mined cell`)
+      }
+    }
+  }
+  return /** @type {Layout} */ (layout)
+}
+
+/**
+ * Pure, Node-runnable board generation: given a size, a mine count, and an
+ * injected RNG, produce a plain layout object — no DOM, no I/O, no `Grid` class
+ * leaking out. This is the headless entry point behind `@cozy-games/mnswpr/core`;
+ * the DOM client reaches the same generator lazily through `MinesweeperRules`.
+ *
+ * The injected `rng` is the determinism seam: the same rng sequence always
+ * yields the same layout. `seed` is a convenience — when no `rng` is given it is
+ * wrapped with {@link mulberry32}, keeping generation reproducible and free of
+ * `Math.random` (invariant #4).
+ *
+ * First-move safety: pass `safeCell: { r, c }` to guarantee that cell is never a
+ * mine — the coordinate-friendly front door to the low-level `exclude` set, so
+ * callers don't have to know the `r * cols + c` key encoding. It merges with any
+ * `exclude` given, and the capacity check below rejects layouts where the mines
+ * can't fit once it's carved out. For 3x3 first-click *flood* safety (the clicked
+ * cell plus its 8 neighbors), see {@link excludeAround}.
+ *
+ * @param {number} rows - number of rows (board height)
+ * @param {number} cols - number of columns (board width)
+ * @param {number} mines - number of mines to place
+ * @param {{ rng?: () => number, seed?: number, exclude?: Set<number>, safeCell?: { r: number, c: number } }} [options]
+ * @returns {Layout} a plain, serializable layout object
+ */
+export function generateBoard(rows, cols, mines, { rng, seed = 0, exclude = NO_EXCLUDE, safeCell } = {}) {
+  if (!Number.isInteger(rows) || !Number.isInteger(cols) || rows < 1 || cols < 1) {
+    throw new RangeError(`generateBoard: rows/cols must be positive integers (got ${rows}x${cols})`)
+  }
+
+  // Resolve the first-move-safe cell into the exclude set (non-mutating: never
+  // touch a caller-owned set). An out-of-bounds safeCell fails loudly rather than
+  // silently excluding nothing and handing back a board that could mine it.
+  let excludeSet = exclude
+  if (safeCell !== undefined) {
+    const { r, c } = safeCell
+    if (!Number.isInteger(r) || !Number.isInteger(c) || r < 0 || c < 0 || r >= rows || c >= cols) {
+      throw new RangeError(`generateBoard: safeCell must be an in-bounds { r, c } (got { r: ${r}, c: ${c} } on ${rows}x${cols})`)
+    }
+    excludeSet = new Set(exclude)
+    excludeSet.add(r * cols + c)
+  }
+
+  const capacity = rows * cols - excludeSet.size
+  if (!Number.isInteger(mines) || mines < 0 || mines > capacity) {
+    throw new RangeError(`generateBoard: mines must be an integer in [0, ${capacity}] (got ${mines})`)
+  }
+
+  const config = { rows, cols, mines }
+  const grid = new Grid(rows, cols, () => ({ mine: false, adjacent: 0, status: 'hidden' }))
+  fillMines(rng ?? mulberry32(seed), config, excludeSet, grid)
+
+  /** @type {LayoutCell[][]} */
+  const cells = []
+  /** @type {[number, number][]} */
+  const mineLocations = []
+  for (let r = 0; r < rows; r++) {
+    /** @type {LayoutCell[]} */
+    const row = []
+    for (let c = 0; c < cols; c++) {
+      const cell = grid.at(r, c)
+      row.push({ mine: cell.mine, adjacent: cell.adjacent })
+      if (cell.mine) mineLocations.push([r, c])
+    }
+    cells.push(row)
+  }
+  return { rows, cols, mines, cells, mineLocations }
+}

packages/mnswpr/core/minesweeper/reveal.js

@@ -0,0 +1,64 @@
+// @ts-check
+import { eightWay } from '../grid/neighbors.js'
+
+/**
+ * @typedef {import('./board.js').Cell} Cell
+ * @typedef {import('../grid/grid.js').Grid<Cell>} MineGrid
+ * @typedef {{ r: number, c: number, adjacent: number }} RevealedCell
+ */
+
+/**
+ * Reveal starting at (r, c) and flood-fill outward while cells are blank (zero
+ * adjacent mines), stopping at numbers and flags. Mutates cell statuses; returns
+ * the newly-revealed cells (never includes already-revealed/flagged cells, so
+ * callers can count these as fresh safe reveals). The start cell must be a known
+ * non-mine, hidden cell.
+ *
+ * @param {MineGrid} grid
+ * @returns {RevealedCell[]}
+ */
+export function floodReveal(grid, startR, startC) {
+  /** @type {RevealedCell[]} */
+  const revealed = []
+  const start = grid.at(startR, startC)
+  start.status = 'revealed'
+  revealed.push({ r: startR, c: startC, adjacent: start.adjacent })
+
+  const queue = [[startR, startC]]
+  while (queue.length) {
+    const [r, c] = queue.shift()
+    // Only blank cells propagate; numbers are a boundary.
+    if (grid.at(r, c).adjacent !== 0) continue
+    for (const [nr, nc] of eightWay(grid, r, c)) {
+      const n = grid.at(nr, nc)
+      if (n.status === 'revealed' || n.status === 'flagged') continue
+      // A blank cell has no adjacent mines, so its neighbors are all safe.
+      n.status = 'revealed'
+      revealed.push({ r: nr, c: nc, adjacent: n.adjacent })
+      if (n.adjacent === 0) queue.push([nr, nc])
+    }
+  }
+  return revealed
+}
+
+/**
+ * @param {MineGrid} grid
+ * @returns {number} count of flagged cells around (r, c)
+ */
+export function countFlagsAround(grid, r, c) {
+  let flags = 0
+  for (const [nr, nc] of eightWay(grid, r, c)) {
+    if (grid.at(nr, nc).status === 'flagged') flags++
+  }
+  return flags
+}
+
+/**
+ * @param {MineGrid} grid
+ * @returns {Array<{ r: number, c: number }>} every mined coordinate
+ */
+export function allMines(grid) {
+  const out = []
+  grid.forEach((cell, r, c) => { if (cell.mine) out.push({ r, c }) })
+  return out
+}

packages/mnswpr/core/minesweeper/rules.js

@@ -0,0 +1,325 @@
+// @ts-check
+import { Grid } from '../grid/grid.js'
+import { toJSON as gridToJSON, fromJSON as gridFromJSON } from '../grid/serialize.js'
+import { eightWay } from '../grid/neighbors.js'
+import { placeMines, excludeAround, validateLayout } from './board.js'
+import { floodReveal, countFlagsAround, allMines } from './reveal.js'
+
+/**
+ * Minesweeper as a pure, deterministic state machine — no DOM, no wall clock.
+ * `GameSession` (Layer 1) drives it; the client renders the events it emits.
+ *
+ * @typedef {import('./board.js').Config} Config
+ * @typedef {import('./board.js').Cell} Cell
+ * @typedef {'fresh' | 'active' | 'won' | 'lost'} Phase
+ * @typedef {{ seed: number, config: Config, grid: Grid<Cell>, phase: Phase, minesPlaced: boolean, revealedSafe: number }} State
+ * @typedef {{ type: 'reveal', r: number, c: number } | { type: 'flag', r: number, c: number } | { type: 'chord', r: number, c: number }} Move
+ * @typedef {object} Event
+ */
+
+/**
+ * The typed move-event vocabulary emitted by the session (one per effective
+ * move). This is the game's public event language — consumed later by the shared
+ * envelope. `type` + `r`/`c` are game meaning (classified here); `t` (injected
+ * clock) and `seq` (monotonic) are stamped by `GameSession` when it emits.
+ *
+ * Note `flag` vs `unflag`: both come from a `flag` move — the distinction is the
+ * outcome (did the toggle set or clear the flag), which only the rules can tell.
+ *
+ * @typedef {'reveal' | 'flag' | 'unflag' | 'chord'} MoveEventType
+ * @typedef {{ type: MoveEventType, r: number, c: number, t: number, seq: number }} MoveEvent
+ */
+
+/** The move-event vocabulary as runtime data (the `MoveEvent` `type` domain). */
+export const MOVE_EVENT_TYPES = /** @type {const} */ (['reveal', 'flag', 'unflag', 'chord'])
+
+const freshCell = () => ({ mine: false, adjacent: 0, status: 'hidden' })
+
+/** Valid game phases and per-cell statuses — the closed sets a snapshot may name. */
+const PHASES = new Set(['fresh', 'active', 'won', 'lost'])
+const CELL_STATUSES = new Set(['hidden', 'flagged', 'revealed'])
+
+/**
+ * Assert a serialized game state (from {@link MinesweeperRules.serialize}, or its
+ * JSON round-trip) is well-formed before reviving it, so a corrupt or truncated
+ * snapshot fails with a clear error instead of quietly producing a broken game.
+ *
+ * @param {unknown} snap
+ */
+function assertStateSnapshot(snap) {
+  if (snap === null || typeof snap !== 'object') {
+    throw new TypeError(`deserialize: expected a state snapshot object (got ${snap === null ? 'null' : typeof snap})`)
+  }
+  const s = /** @type {any} */ (snap)
+  if (typeof s.seed !== 'number') throw new TypeError('deserialize: snapshot.seed must be a number')
+  const cfg = s.config
+  if (cfg === null || typeof cfg !== 'object' || !Number.isInteger(cfg.rows) || !Number.isInteger(cfg.cols) || !Number.isInteger(cfg.mines)) {
+    throw new TypeError('deserialize: snapshot.config must be { rows, cols, mines } integers')
+  }
+  if (!PHASES.has(s.phase)) throw new RangeError(`deserialize: snapshot.phase must be one of ${[...PHASES].join('/')} (got ${JSON.stringify(s.phase)})`)
+  if (typeof s.minesPlaced !== 'boolean') throw new TypeError('deserialize: snapshot.minesPlaced must be a boolean')
+  if (!Number.isInteger(s.revealedSafe) || s.revealedSafe < 0) throw new RangeError('deserialize: snapshot.revealedSafe must be a non-negative integer')
+  const g = s.grid
+  if (g === null || typeof g !== 'object' || !Number.isInteger(g.rows) || !Number.isInteger(g.cols) || !Array.isArray(g.cells)) {
+    throw new TypeError('deserialize: snapshot.grid must be { rows, cols, cells[] }')
+  }
+  if (g.rows !== cfg.rows || g.cols !== cfg.cols) {
+    throw new RangeError(`deserialize: grid ${g.rows}x${g.cols} disagrees with config ${cfg.rows}x${cfg.cols}`)
+  }
+  if (g.cells.length !== g.rows * g.cols) {
+    throw new RangeError(`deserialize: grid.cells must have ${g.rows * g.cols} entries (got ${g.cells.length})`)
+  }
+  for (let i = 0; i < g.cells.length; i++) {
+    const cell = g.cells[i]
+    if (cell === null || typeof cell !== 'object' || typeof cell.mine !== 'boolean' || !Number.isInteger(cell.adjacent) || !CELL_STATUSES.has(cell.status)) {
+      throw new TypeError(`deserialize: grid.cells[${i}] must be { mine: boolean, adjacent: integer, status: hidden/flagged/revealed }`)
+    }
+  }
+}
+
+/** @param {State} state */
+function isWin(state) {
+  const { rows, cols, mines } = state.config
+  return state.revealedSafe >= rows * cols - mines
+}
+
+/**
+ * Reveal a single cell (with first-click safety and flood-fill).
+ * @param {State} state
+ * @returns {{ state: State, events: Event[] }}
+ */
+function reveal(state, r, c) {
+  const cell = state.grid.at(r, c)
+  if (!cell || cell.status !== 'hidden') return { state, events: [] }
+
+  // First reveal: generate the board now, excluding this cell's neighborhood, so
+  // the opening click is always safe and the seed fully determines the layout.
+  // Injected boards (fromLayout) arrive with minesPlaced already true and skip
+  // this — their opening reveal plays exactly as the layout dictates.
+  if (!state.minesPlaced) {
+    placeMines(state.seed, state.config, excludeAround(state.config, r, c), state.grid)
+    state.minesPlaced = true
+  }
+  // fresh → active on the first real reveal, whether the board was just generated
+  // or injected pre-built — decoupled from placement so both paths transition the
+  // same way.
+  if (state.phase === 'fresh') state.phase = 'active'
+
+  if (cell.mine) {
+    cell.status = 'revealed'
+    state.phase = 'lost'
+    return { state, events: [{ type: 'explode', r, c, mines: allMines(state.grid) }] }
+  }
+
+  const revealed = floodReveal(state.grid, r, c)
+  state.revealedSafe += revealed.length
+  /** @type {Event[]} */
+  const events = [{ type: 'reveal', cells: revealed }]
+  if (isWin(state)) { state.phase = 'won'; events.push({ type: 'win' }) }
+  return { state, events }
+}
+
+/**
+ * Toggle a flag on a hidden cell.
+ * @param {State} state
+ * @returns {{ state: State, events: Event[] }}
+ */
+function flag(state, r, c) {
+  const cell = state.grid.at(r, c)
+  if (!cell || cell.status === 'revealed') return { state, events: [] }
+  cell.status = cell.status === 'flagged' ? 'hidden' : 'flagged'
+  return { state, events: [{ type: 'flag', r, c, flagged: cell.status === 'flagged' }] }
+}
+
+/**
+ * Chord: on a revealed number whose adjacent flags equal its value, reveal every
+ * non-flagged neighbor (any of which may be a mine → loss).
+ * @param {State} state
+ * @returns {{ state: State, events: Event[] }}
+ */
+function chord(state, r, c) {
+  const { grid } = state
+  const cell = grid.at(r, c)
+  if (!cell || cell.status !== 'revealed' || cell.adjacent === 0) return { state, events: [] }
+  if (countFlagsAround(grid, r, c) !== cell.adjacent) return { state, events: [] }
+
+  /** @type {import('./reveal.js').RevealedCell[]} */
+  const revealedCells = []
+  for (const [nr, nc] of eightWay(grid, r, c)) {
+    const n = grid.at(nr, nc)
+    if (n.status !== 'hidden') continue
+    if (n.mine) {
+      n.status = 'revealed'
+      state.phase = 'lost'
+      return { state, events: [{ type: 'explode', r: nr, c: nc, mines: allMines(grid) }] }
+    }
+    for (const rev of floodReveal(grid, nr, nc)) revealedCells.push(rev)
+  }
+  state.revealedSafe += revealedCells.length
+
+  /** @type {Event[]} */
+  const events = []
+  if (revealedCells.length) events.push({ type: 'reveal', cells: revealedCells })
+  if (isWin(state)) { state.phase = 'won'; events.push({ type: 'win' }) }
+  return { state, events }
+}
+
+/**
+ * Project full state down to what a client is allowed to know: revealed cells
+ * (+ their adjacency), flags, and — only once the game is over — the mines. An
+ * unrevealed mine is NEVER included mid-game, so this is safe to send over a wire
+ * (invariant #3). Hidden, unrevealed, non-mine cells are simply omitted.
+ *
+ * @param {State} state
+ */
+function project(state) {
+  const terminal = state.phase === 'won' || state.phase === 'lost'
+  const cells = []
+  state.grid.forEach((cell, r, c) => {
+    if (cell.status === 'revealed') cells.push({ r, c, status: 'revealed', adjacent: cell.adjacent, mine: cell.mine })
+    else if (cell.status === 'flagged') cells.push({ r, c, status: 'flagged' })
+    else if (terminal && cell.mine) cells.push({ r, c, status: 'hidden', mine: true })
+  })
+  return { config: state.config, phase: state.phase, cells }
+}
+
+/**
+ * The GameRules contract consumed by GameSession/replay: init / apply / status /
+ * project, plus serialize / deserialize for snapshotting. Deterministic and
+ * DOM-free.
+ */
+export const MinesweeperRules = {
+  /**
+   * @param {number} seed
+   * @param {Config} config
+   * @returns {State}
+   */
+  init(seed, config) {
+    return {
+      seed,
+      config,
+      grid: new Grid(config.rows, config.cols, freshCell),
+      phase: 'fresh',
+      minesPlaced: false,
+      revealedSafe: 0
+    }
+  },
+
+  /**
+   * Build a game state from an explicit, pre-built layout (as returned by
+   * `generateBoard`) instead of generating one from a seed. Parallel to
+   * {@link init}: it yields a `State` a `GameSession` can drive identically —
+   * same rules, same transitions — the only difference being that the board is
+   * fixed up front, so the opening reveal is NOT made safe (first-click safety is
+   * a property of internal generation, not of a caller-supplied board). The
+   * layout is validated first and a malformed one throws.
+   *
+   * @param {import('./board.js').Layout} layout
+   * @param {{ seed?: number }} [opts] - seed is metadata only (no generation happens); defaults to 0
+   * @returns {State}
+   */
+  fromLayout(layout, { seed = 0 } = {}) {
+    validateLayout(layout)
+    const { rows, cols, mines } = layout
+    return {
+      seed,
+      config: { rows, cols, mines },
+      grid: new Grid(rows, cols, (r, c) => ({
+        mine: layout.cells[r][c].mine,
+        adjacent: layout.cells[r][c].adjacent,
+        status: 'hidden'
+      })),
+      phase: 'fresh',
+      minesPlaced: true,
+      revealedSafe: 0
+    }
+  },
+
+  /** @param {State} state @returns {Phase} */
+  status(state) {
+    return state.phase
+  },
+
+  /**
+   * Fold a move into the state. Terminal states are absorbing.
+   * @param {State} state
+   * @param {Move} move
+   * @returns {{ state: State, events: Event[] }}
+   */
+  apply(state, move) {
+    if (state.phase === 'won' || state.phase === 'lost') return { state, events: [] }
+    switch (move.type) {
+      case 'reveal': return reveal(state, move.r, move.c)
+      case 'flag': return flag(state, move.r, move.c)
+      case 'chord': return chord(state, move.r, move.c)
+      default: return { state, events: [] }
+    }
+  },
+
+  project,
+
+  /**
+   * Classify an applied move into a typed move-event kind, or `null` if the move
+   * was a no-op (the rules produced no events — e.g. clicking a revealed cell).
+   * The session stamps the returned `{ type, r, c }` with `t` and `seq`. This is
+   * the seam that turns a raw `Move` into the {@link MoveEvent} vocabulary and,
+   * critically, splits a `flag` move into `flag`/`unflag` by its outcome.
+   *
+   * @param {Move} move
+   * @param {Event[]} events - the rules events this move produced
+   * @returns {{ type: MoveEventType, r: number, c: number } | null}
+   */
+  toMoveEvent(move, events) {
+    if (!events || events.length === 0) return null
+    switch (move.type) {
+      case 'reveal': return { type: 'reveal', r: move.r, c: move.c }
+      case 'chord': return { type: 'chord', r: move.r, c: move.c }
+      case 'flag': {
+        const flagged = events.find(e => e.type === 'flag')
+        if (!flagged) return null
+        return { type: flagged.flagged ? 'flag' : 'unflag', r: move.r, c: move.c }
+      }
+      default: return null
+    }
+  },
+
+  /**
+   * Snapshot a game state as a plain, JSON-safe object: the whole board (every
+   * cell's mine/adjacent/status, via the Layer-0 grid serializer) plus phase and
+   * progress. Inverse of {@link deserialize}. The `grid` instance is the only
+   * non-JSON-safe field of `State`; everything else (seed, config, flags) is
+   * already plain data.
+   *
+   * @param {State} state
+   * @returns {{ seed: number, config: Config, phase: Phase, minesPlaced: boolean, revealedSafe: number, grid: { rows: number, cols: number, cells: Cell[] } }}
+   */
+  serialize(state) {
+    return {
+      seed: state.seed,
+      config: state.config,
+      phase: state.phase,
+      minesPlaced: state.minesPlaced,
+      revealedSafe: state.revealedSafe,
+      grid: gridToJSON(state.grid)
+    }
+  },
+
+  /**
+   * Rebuild a game state from {@link serialize} output (or its JSON round-trip).
+   * Cells are cloned so the revived state shares no references with the snapshot.
+   *
+   * @param {ReturnType<typeof MinesweeperRules.serialize>} snap
+   * @returns {State}
+   */
+  deserialize(snap) {
+    assertStateSnapshot(snap)
+    return {
+      seed: snap.seed,
+      config: snap.config,
+      phase: snap.phase,
+      minesPlaced: snap.minesPlaced,
+      revealedSafe: snap.revealedSafe,
+      grid: gridFromJSON(snap.grid, cell => ({ ...cell }))
+    }
+  }
+}

packages/mnswpr/core/session/replay.js

@@ -0,0 +1,41 @@
+// @ts-check
+
+/**
+ * Deterministically re-run a submitted game from `{ seed, config, log }` and
+ * report the authoritative outcome. A server calls this at submit time to verify
+ * a score without trusting the client: it recomputes the result and time from the
+ * moves, and rejects logs that don't terminate or whose timestamps aren't
+ * monotonic. (The "verifiable-replay" anti-cheat path — no live server needed.)
+ *
+ * @param {{ init: Function, apply: Function, status: Function }} rules
+ * @param {{ seed: number, config: object, log: Array<{ move: object, t: number }> }} submission
+ * @returns {{ status: string, time: number, valid: boolean, reason: string | null }}
+ */
+export function replay(rules, { seed, config, log }) {
+  let state = rules.init(seed, config)
+  let monotonic = true
+  let prevT = -Infinity
+  let t0 = null
+  let tEnd = null
+
+  for (const { move, t } of log) {
+    if (t < prevT) monotonic = false
+    prevT = t
+    const before = rules.status(state)
+    state = rules.apply(state, move).state
+    const after = rules.status(state)
+    if (before === 'fresh' && after !== 'fresh' && t0 === null) t0 = t
+    if ((after === 'won' || after === 'lost') && tEnd === null) tEnd = t
+  }
+
+  const status = rules.status(state)
+  const terminal = status === 'won' || status === 'lost'
+  const time = t0 !== null && tEnd !== null ? tEnd - t0 : 0
+  const valid = monotonic && terminal
+  const reason = valid
+    ? null
+    : !monotonic
+      ? 'non-monotonic timestamps'
+      : 'log does not reach a terminal state'
+  return { status, time, valid, reason }
+}

packages/mnswpr/core/session/rng.js

@@ -0,0 +1,29 @@
+// @ts-check
+
+/**
+ * Deterministic, seedable PRNG (mulberry32). A given seed always yields the same
+ * sequence — this is what makes board generation reproducible and `replay()`
+ * possible. Uses `Math.imul` (integer math), NOT `Math.random`, so it stays
+ * inside the determinism guard.
+ *
+ * @param {number} seed - any 32-bit integer
+ * @returns {() => number} a function returning floats in [0, 1)
+ */
+export function mulberry32(seed) {
+  let a = seed >>> 0
+  return function () {
+    a = (a + 0x6D2B79F5) | 0
+    let t = Math.imul(a ^ (a >>> 15), 1 | a)
+    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t
+    return ((t ^ (t >>> 14)) >>> 0) / 4294967296
+  }
+}
+
+/**
+ * Integer in [0, n) from an rng function.
+ * @param {() => number} rng
+ * @param {number} n
+ */
+export function randInt(rng, n) {
+  return Math.floor(rng() * n)
+}

packages/mnswpr/core/session/session.js

@@ -0,0 +1,174 @@
+// @ts-check
+
+/**
+ * Layer 1 — owns lifecycle, the (injected) clock, and the move log; delegates all
+ * game meaning to an injected `rules` object. This is where timing authority
+ * lives: on the client `clock` is `Date.now` (cosmetic); on a server it is the
+ * server's clock (authoritative). The session never calls a wall clock itself.
+ * Future home: @cozy-games/game-session.
+ *
+ * @typedef {{ init: Function, apply: Function, status: Function, project: Function, serialize?: Function, deserialize?: Function, toMoveEvent?: Function }} Rules
+ */
+export class GameSession {
+  /**
+   * Start from either `{ seed, config }` (the rules generate the board) or a
+   * pre-built `{ state }` (e.g. a rules factory that injected an explicit board);
+   * `state` wins when both are given. The session stays generic — it just holds
+   * whatever state the rules produced.
+   *
+   * @param {Rules} rules
+   * @param {{ seed?: number, config?: object, state?: object, clock?: () => number }} opts
+   */
+  constructor(rules, { seed, config, state, clock = () => 0 }) {
+    this.rules = rules
+    this.clock = clock
+    this.state = state ?? rules.init(seed, config)
+    /** @type {Array<{ move: object, t: number }>} */
+    this._log = []
+    this._t0 = null
+    this._tEnd = null
+    // Move-event emission: subscribers + a monotonic sequence counter (last seq
+    // assigned; 0 = none yet). Seq is part of the snapshot so it keeps rising
+    // across a resume rather than restarting.
+    /** @type {Set<(event: object) => void>} */
+    this._moveHandlers = new Set()
+    this._seq = 0
+  }
+
+  /**
+   * Subscribe to typed move-events — one per effective move (reveal / flag /
+   * unflag / chord), each carrying `{ type, r, c, t, seq }`. Returns an
+   * unsubscribe function. Pure in-process pub/sub: no DOM, no rendering. Requires
+   * the rules to implement `toMoveEvent`.
+   *
+   * @param {(event: object) => void} handler
+   * @returns {() => void} unsubscribe
+   */
+  onMove(handler) {
+    this._moveHandlers.add(handler)
+    return () => this._moveHandlers.delete(handler)
+  }
+
+  /**
+   * Apply a move: stamp it, fold it through the rules, and return the projected
+   * view + events + authoritative elapsed time.
+   * @param {object} move
+   */
+  applyMove(move) {
+    const t = this.clock()
+    const before = this.rules.status(this.state)
+    const { state, events } = this.rules.apply(this.state, move)
+    this.state = state
+    this._log.push({ move, t })
+
+    const after = this.rules.status(state)
+    // Timer starts on the first move that leaves 'fresh' (the opening reveal).
+    if (before === 'fresh' && after !== 'fresh' && this._t0 === null) this._t0 = t
+    if ((after === 'won' || after === 'lost') && this._tEnd === null) this._tEnd = t
+
+    // Emit a typed move-event for effective moves (rules classify; no-ops → null).
+    if (typeof this.rules.toMoveEvent === 'function') {
+      const kind = this.rules.toMoveEvent(move, events)
+      if (kind) this._emitMove({ ...kind, t, seq: ++this._seq })
+    }
+
+    return { events, view: this.rules.project(state), time: this.elapsed() }
+  }
+
+  /** @param {object} event */
+  _emitMove(event) {
+    for (const handler of this._moveHandlers) handler(event)
+  }
+
+  status() {
+    return this.rules.status(this.state)
+  }
+
+  view() {
+    return this.rules.project(this.state)
+  }
+
+  log() {
+    return this._log.slice()
+  }
+
+  /** Authoritative elapsed ms: first move → terminal move (or → now if ongoing). */
+  elapsed() {
+    if (this._t0 === null) return 0
+    const end = this._tEnd !== null ? this._tEnd : this.clock()
+    return end - this._t0
+  }
+
+  /** The signed-off result, or null while the game is still in progress. */
+  result() {
+    const status = this.status()
+    if (status !== 'won' && status !== 'lost') return null
+    return { status, time: this.elapsed(), seed: this.state.seed, config: this.state.config, log: this.log() }
+  }
+
+  /**
+   * Full, JSON-safe snapshot of the whole session — game state (board + per-cell
+   * status, via the rules' own serializer) plus the move log and timing anchors
+   * (`t0`/`tEnd`) that `elapsed()` derives from. Everything needed to later resume
+   * (core-05); the live `clock` is deliberately excluded (it's re-injected on
+   * {@link GameSession.deserialize}). Requires the rules to implement `serialize`.
+   *
+   * @returns {{ state: object, log: Array<{ move: object, t: number }>, t0: number | null, tEnd: number | null, seq: number }}
+   */
+  serialize() {
+    if (typeof this.rules.serialize !== 'function') {
+      throw new TypeError('GameSession.serialize: rules must implement serialize(state)')
+    }
+    return {
+      state: this.rules.serialize(this.state),
+      log: this._log.map(({ move, t }) => ({ move, t })),
+      t0: this._t0,
+      tEnd: this._tEnd,
+      seq: this._seq
+    }
+  }
+
+  /**
+   * Rebuild a session from a {@link serialize} snapshot (or its JSON round-trip).
+   * The clock is re-injected — it's a live function, not serializable — while the
+   * log and timing anchors are restored so `elapsed()` resumes correctly.
+   * Requires the rules to implement `deserialize`.
+   *
+   * @param {Rules} rules
+   * @param {{ state: object, log: Array<{ move: object, t: number }>, t0: number | null, tEnd: number | null }} snapshot
+   * @param {{ clock?: () => number }} [opts]
+   * @returns {GameSession}
+   */
+  static deserialize(rules, snapshot, { clock = () => 0 } = {}) {
+    if (typeof rules.deserialize !== 'function') {
+      throw new TypeError('GameSession.deserialize: rules must implement deserialize(snapshot)')
+    }
+    if (snapshot === null || typeof snapshot !== 'object') {
+      throw new TypeError(`GameSession.deserialize: expected a snapshot object (got ${snapshot === null ? 'null' : typeof snapshot})`)
+    }
+    const { state, log, t0, tEnd, seq } = snapshot
+    if (!Array.isArray(log)) {
+      throw new TypeError('GameSession.deserialize: snapshot.log must be an array')
+    }
+    for (const entry of log) {
+      if (entry === null || typeof entry !== 'object' || typeof entry.t !== 'number' || entry.move === null || typeof entry.move !== 'object') {
+        throw new TypeError('GameSession.deserialize: each log entry must be { move: object, t: number }')
+      }
+    }
+    if (!(t0 === null || typeof t0 === 'number') || !(tEnd === null || typeof tEnd === 'number')) {
+      throw new TypeError('GameSession.deserialize: snapshot.t0/tEnd must each be a number or null')
+    }
+    if (!(seq === undefined || (Number.isInteger(seq) && seq >= 0))) {
+      throw new TypeError('GameSession.deserialize: snapshot.seq must be a non-negative integer')
+    }
+    // rules.deserialize validates and revives the game-state half.
+    const session = new GameSession(rules, { state: rules.deserialize(state), clock })
+    session._log = log.map(({ move, t }) => ({ move, t }))
+    session._t0 = t0
+    session._tEnd = tEnd
+    // Continue the sequence where it left off so move-event seq keeps rising
+    // across a resume (absent in a pre-move-event snapshot ⇒ start at 0).
+    session._seq = seq ?? 0
+    return session
+  }
+}

packages/mnswpr/docs/headless-core-and-client-design.md

@@ -0,0 +1,437 @@
+# Headless core + client design — `@cozy-games/mnswpr/core` and the client that consumes it
+
+Design for splitting the Minesweeper engine into a **headless, isomorphic core**
+(runs identically in a browser or on a server) and a **thin client** that renders
+it. The core is internally layered so the generic bottom can later be lifted out
+into `@cozy-games/grid` + `@cozy-games/game-session` once a second game (Sudoku)
+exists to validate the abstraction. We are **not** building the generic grid
+engine now — only structuring for it.
+
+Goals, in priority order:
+
+1. **Headless core** — game state is a plain data model, no DOM, no wall clock.
+2. **Authoritative-host capable** — the same core can run on a host that owns
+   the RNG, the clock, and the move sequence, so game state and timing can be
+   computed by an authoritative host rather than solely on the client.
+3. **Backwards compatible** — the existing DOM UI, CSS, and jsdom tests keep
+   working; today's offline play is just "the core with a local transport."
+4. **Extraction-ready** — a clean seam between generic (grid/session) and
+   Minesweeper-specific (mines/reveal) code.
+
+---
+
+## 1. Package layout & the seam
+
+**Decision (settled): one published package, core exposed as a sub-path.** Open-
+source consumers keep installing a single `@cozy-games/mnswpr` and get the headless
+core for free at `@cozy-games/mnswpr/core` — no second package to publish, version,
+or document. The DOM client stays the default entry (`.`).
+
+```
+packages/mnswpr/                 # @cozy-games/mnswpr — ONE published package
+  mnswpr.js                      # "."       → DOM client (browser entry; today's default)
+  levels.js                      # shared by client + core (level presets)
+  core/                          # "./core"  → headless, isomorphic, ZERO DOM, ZERO wall-clock
+    index.js                     #   the sub-path entry — public core API
+    grid/                        #   Layer 0  → future @cozy-games/grid
+      grid.js                    #     Grid<Cell> container, coords, inBounds
+      neighbors.js               #     neighbor STRATEGIES (eightWay, orthogonal, …)
+      serialize.js
+    session/                     #   Layer 1  → future @cozy-games/game-session
+      session.js                 #     GameSession: lifecycle, injected clock, move log
+      rng.js                     #     seedable deterministic PRNG (mulberry32)
+      replay.js                  #     replay(rules, {seed, config, log}) → validate
+    minesweeper/                 #   Layer 2  → Minesweeper-specific rules
+      rules.js                   #     GameRules impl: init/apply/status/project
+      board.js                   #     deterministic board gen + first-click safety
+      reveal.js                  #     flood-fill, chording
+  client/                        # DOM client internals (consume ./core)
+    renderer.js                  #   events → DOM (the ONLY place document is touched) — EXTRACTED
+    transport.js                 #   LocalTransport (RemoteTransport added later) — EXTRACTED
+    # Decision: the input state machine (mouse/touch/chording/long-press) and the
+    # timer stay INLINE in mnswpr.js for now — not extracted to input-adapter.js /
+    # timer-view.js. The input code is intricate and under-tested (no chord/touch/
+    # middle-click coverage yet), so extraction is deferred until those
+    # characterization tests exist or a concrete need arises. See §9.
+```
+
+`package.json` `exports` (sub-path is the only surface change consumers see):
+
+```jsonc
+"exports": {
+  ".":        { "default": "./dist/mnswpr.js" },  // DOM client (browser) — unchanged default
+  "./core":   { "default": "./core/index.js" },   // headless, isomorphic core (source ESM)
+  "./dist/*": { "default": "./dist/*" },
+  "./*":      { "default": "./*" }
+}
+```
+
+- `import mnswpr from '@cozy-games/mnswpr'` → DOM client, exactly as today.
+- `import { GameSession, MinesweeperRules } from '@cozy-games/mnswpr/core'` → headless.
+  The core entry pulls in **zero DOM**, so a server (later) imports it without
+  dragging in browser code, and the browser bundle for `.` never includes the
+  core's server-only helpers.
+
+**The seam** = the boundary *inside* `core/` between `grid/` + `session/`
+(generic) and `minesweeper/` (specific). Exposing the core via a sub-path does
+**not** compromise the future extraction — the publish surface and the internal
+layering are orthogonal. Rules of the seam:
+
+- `grid/` and `session/` **never import** `minesweeper/`.
+- `minesweeper/` depends on `grid/` + `session/` only through their public
+  interfaces (below) — no reaching into internals.
+- Anything Minesweeper-specific that leaks *down* (8-way adjacency, "mine",
+  "reveal") is a bug in the layering. Adjacency is **injected**, not assumed.
+
+When Sudoku lands, `core/grid/` and `core/session/` move out verbatim into
+`@cozy-games/grid` + `@cozy-games/game-session`; `core/minesweeper/` (and a new
+`sudoku/`) depend on them, and `@cozy-games/mnswpr/core` re-exports from them so the
+consumer-facing sub-path is unchanged.
+
+---
+
+## 2. Layer 0 — generic grid (`grid/`)
+
+A dumb, dense 2D container of opaque cells. Knows nothing about game meaning.
+
+```js
+// Coord is a plain [r, c] tuple everywhere (cheap, serializable).
+// Grid<Cell> — Cell is opaque to this layer.
+class Grid {
+  constructor(rows, cols, fill)          // fill: (r, c) => Cell
+  get rows(); get cols()
+  at(r, c)                               // → Cell   (throws/undefined out of bounds)
+  set(r, c, cell)
+  inBounds(r, c)                         // → boolean
+  forEach(fn)                            // fn(cell, r, c)
+  map(fn)                                // → Grid of new cells
+  clone()
+}
+
+// Neighbor STRATEGY — the critical extraction seam. Injected, never baked in.
+// eightWay is Minesweeper's; Sudoku would inject `peers` (row ∪ col ∪ box).
+const eightWay      = (grid, r, c) => [...8 in-bounds diagonal+orthogonal coords]
+const orthogonal    = (grid, r, c) => [...4 in-bounds N/E/S/W coords]
+```
+
+`serialize.js`: `toJSON(grid)` / `fromJSON(data, reviveCell)` — used by the
+session for the move log and by the server for persistence/replay.
+
+---
+
+## 3. Layer 1 — generic session & host authority (`session/`)
+
+The most reusable layer, and the one that makes an authoritative host possible. It
+owns **lifecycle, time, and the move log**, and delegates game meaning to an
+injected `GameRules` object.
+
+### The rules contract (what any game implements)
+
+```js
+/**
+ * @template State, Move, Event
+ * A pure, deterministic game definition. NO Date, NO Math.random, NO DOM.
+ */
+const GameRules = {
+  init(seed, config),                    // → State           (deterministic from seed)
+  apply(state, move, rng),               // → { state, events } (pure; rng passed in)
+  status(state),                         // → 'active' | 'won' | 'lost'
+  project(state)                         // → ClientView       (hides secrets; see §4)
+}
+```
+
+### The session
+
+```js
+class GameSession {
+  /**
+   * @param rules   a GameRules implementation
+   * @param opts.seed   number   — seeds board gen + RNG (host-held when a host owns the session)
+   * @param opts.config game config (level/difficulty)
+   * @param opts.clock  () => number — INJECTED time source (whoever runs the session owns it)
+   */
+  constructor(rules, opts)
+
+  applyMove(move)        // stamps t=clock(); appends {move, t} to log;
+                         // rules.apply(...); returns projected events + view.
+  status()               // 'active' | 'won' | 'lost'
+  view()                 // rules.project(state) — safe to send to a client
+  elapsed()              // authoritative: t(last decisive move) − t(first move)
+  log()                  // [{move, t}]  — the audit trail
+  result()               // on terminal: { status, time, seed, config, log }
+}
+```
+
+Two decisions that unlock everything:
+
+- **Injected clock.** The session never calls `Date.now()`. The *caller* supplies
+  the clock. On the client it's `Date.now`. On an authoritative host it's the
+  host's clock — so `elapsed()` is owned by whoever runs the session.
+- **Injected, seedable RNG** (`rng.js`, e.g. mulberry32 seeded by `opts.seed`).
+  Board generation is a pure function of `seed` (+ first click), so a run is
+  **bit-for-bit reproducible**. A host that owns the session holds the seed and
+  sends only projected views, so unrevealed board state need not be sent to the
+  client mid-game.
+
+### Replay (`replay.js`)
+
+```js
+// Re-runs a game from scratch from its recorded inputs and returns the
+// recomputed outcome. A host can use this to validate a submitted
+// { seed, config, log }:
+//   - does the log actually solve the board?
+//   - is the move timeline monotonic and within plausible bounds?
+//   - does the recomputed time match the recorded time?
+replay(rules, { seed, config, log }) // → { status, time, valid, reason? }
+```
+
+Because the core is deterministic, a full game can be reconstructed from its
+inputs alone — no live per-move host needed; `replay()` can run wherever a host
+processes a submission. It requires exactly this headless core and nothing else.
+
+> **Determinism is a hard rule for Layers 1–2:** no `Date.now()`, no
+> `Math.random()`, no `new Date()` inside core logic — all injected. This is what
+> makes replay reproducible and tests deterministic. (Same constraint we already
+> follow elsewhere in the repo.)
+
+---
+
+## 4. Layer 2 — Minesweeper rules (`minesweeper/`)
+
+### State (plain data — the DOM's job is gone)
+
+```js
+// Cell — replaces the <td> + data-status/data-value attributes.
+Cell = { mine: boolean, adjacent: number, status: 'hidden' | 'flagged' | 'revealed' }
+
+// State
+{
+  grid: Grid<Cell>,
+  config: { rows, cols, mines, id },     // from levels.js
+  phase: 'fresh' | 'active' | 'won' | 'lost',
+  minesPlaced: boolean                   // false until the first reveal (safety)
+}
+```
+
+### Moves (intents — what the client sends)
+
+```js
+Move =
+  | { type: 'reveal', r, c }
+  | { type: 'flag',   r, c }             // toggle
+  | { type: 'chord',  r, c }             // reveal neighbors when flag-count satisfied
+```
+
+### Events (deltas — what the renderer/server emits)
+
+```js
+Event =
+  | { type: 'reveal',  cells: [{ r, c, adjacent }] }   // whole flood-filled region
+  | { type: 'flag',    r, c, flagged: boolean }
+  | { type: 'explode', r, c, mines: [{ r, c }] }        // loss reveal
+  | { type: 'win' }
+```
+
+Emitting **deltas** (not full state) is what lets the client render incrementally
+*and* lets an authoritative host withhold the rest of the board.
+
+### First-click safety, done right
+
+Generate the board **on the first reveal**, from `(seed, firstClick, config)`,
+excluding the first cell and its neighbors from mine placement. Replaces today's
+`transferMine()` relocation. Benefits: nothing exists to leak before move 1, the
+first click is provably safe, and generation stays a pure seed function.
+
+### `reveal.js`
+
+- Flood-fill of the connected zero-adjacency region (ports `handleEmpty`), returns
+  the revealed cells as one `reveal` event.
+- Chording (ports the left+right behavior), returns a `reveal` or `explode`.
+- Win = every non-mine cell revealed. Loss = a mine revealed.
+
+### Hidden-information projection (`project.js`)
+
+```js
+project(state) // → ClientView
+```
+
+Returns only what a client is allowed to know: revealed cells + their adjacency,
+flags, and phase. **Unrevealed mine positions are never included** (until a
+terminal `explode`/`win`, when the full board is disclosed for the reveal
+animation). A host sends `view()` / event deltas — never the raw state, never the
+seed. A client therefore cannot see unrevealed mines even if it inspects every
+byte it receives.
+
+---
+
+## 5. The client (`packages/mnswpr` → consumer of the core)
+
+The client keeps today's look, CSS, and DOM shape (`<table>` with
+`game-status` / `data-status` / `data-value`) — but it becomes a **consumer** of
+core state, not the owner of it. Four parts:
+
+```
+ InputAdapter          Transport                 Renderer          TimerView
+ (gestures → Move) ──▶ (Local | Remote) ──▶ Event[] ──▶ (deltas → DOM)   (time → DOM)
+                          │
+                          ├─ Local : in-process GameSession  (offline / npm engine)
+                          └─ Remote: HTTP/WS to a host        (authoritative host)
+```
+
+### Transport — one interface, two implementations (mirrors the leaderboard adapter pattern)
+
+```js
+// The client talks ONLY to this — it never knows if the game runs here or on a server.
+Transport = {
+  start(config)          // → { view, time }         begin a game
+  send(move)             // → { events, view, time } apply a move
+  onEvent(cb)            // (Remote may push server events; Local resolves inline)
+  result()               // → { status, time, … } when terminal
+}
+```
+
+- **`LocalTransport`** wraps a `GameSession` with `clock = Date.now`. This is
+  today's behavior exactly: fast, offline, timing owned by the client — fine for
+  offline play and the standalone npm engine.
+- **`RemoteTransport`** forwards moves to a host, which holds the authoritative
+  `GameSession`, and streams back projected events. Timing is host-owned. Used
+  when a game runs on an authoritative host.
+
+### Renderer
+
+`render(container, view)` builds the initial `<table>`; `applyEvents(events)`
+mutates the DOM from deltas. This is the *only* place `document` is touched. It
+reuses the current markup/attributes so existing CSS and the jsdom tests survive.
+(It is basically today's DOM-building code, inverted: driven by events instead of
+owning state.)
+
+### InputAdapter
+
+Keep the existing mouse/touch state machine (left/right/middle, chording,
+long-press-to-flag, `isBusy` debounce) — but instead of mutating the DOM, it
+**emits `Move` intents** to the transport. This is the trickiest existing code;
+porting it as "same gestures, different output" keeps the hard-won input feel.
+
+### TimerView & `gameDone`
+
+- `TimerService` splits in two: the **authoritative clock** moves into
+  `GameSession` (injected); the **display** becomes a dumb `TimerView` that shows
+  `transport`-reported time. In Remote mode it shows server time (optionally a
+  locally-interpolated estimate reconciled on each server message).
+- The current `hooks.gameDone(game)` fires from the terminal event. In **Local**
+  mode the client builds `game` as today. In **Remote** mode the **host**
+  produces the authoritative `{ time, status }` and records the leaderboard
+  result — the client renders it rather than computing it.
+
+The public constructor stays hook-shaped for compatibility, e.g.:
+
+```js
+Minesweeper(appId, version, {
+  transport: new LocalTransport({ level }),   // or RemoteTransport({ endpoint })
+  levelChanged(setting) { … },
+  gameDone(game) { … }                         // Local: client-built; Remote: host-authoritative
+})
+```
+
+---
+
+## 6. Two run modes, one codebase
+
+| | **Local / offline** | **Authoritative host** |
+|---|---|---|
+| Where the core runs | in the browser | on a host |
+| Clock | `Date.now` | host clock |
+| Board/seed | in browser | host-held, sent as rules allow |
+| Transport | `LocalTransport` | `RemoteTransport` |
+| Needs a host tier | no | yes (Function/Worker + session store) |
+| Use | offline play, published npm engine | host-owned sessions |
+
+The published `@cozy-games/mnswpr` stays fully functional standalone (Local mode).
+Running on a host opts into Remote. Same renderer, same input, same rules.
+
+---
+
+## 7. Server-readiness invariants (the offline build MUST hold these)
+
+Going offline-first is only "server-easy later" if the offline build refuses a few
+tempting in-process shortcuts. Each maps to a concrete failure if violated. These
+are the disciplines that make the server additive rather than a rewrite:
+
+1. **Transport is `async`.** `send(move)` returns a Promise (or fires a callback)
+   even though `LocalTransport` resolves instantly. *Violation:* client code
+   assumes synchronous returns → every `RemoteTransport` call breaks.
+2. **Only serializable messages cross the Transport.** Moves in; Events + a
+   projected view out; plain JSON. Never hand the client a live `GameSession`,
+   `Grid`, or `State`. *Violation:* nothing survives a network hop.
+3. **The Renderer consumes only `project(state)` + events** — never raw mine
+   positions, even offline where it technically has them. *Violation:* host mode
+   (which withholds unrevealed board state) needs a renderer rewrite; hidden-
+   information projection stops being a drop-in.
+4. **The core is deterministic now** — seeded RNG + injected clock + a working
+   `replay()`, even though offline play doesn't need them. *Violation:*
+   retrofitting determinism into board generation later is a rewrite, and the
+   replay/validation path has no substrate.
+5. **The client is stateless about rules.** All win/loss/reveal logic lives in the
+   core; the client only renders. *Violation:* client-side rule shortcuts aren't
+   authoritative on a server.
+
+A determinism guard (see §10 Testing) fails the build if `Date`/`Math.random`
+appear in `core/` outside the injected `clock`/`rng` seams.
+
+## 8. Mapping from today's engine
+
+| Today (`packages/mnswpr/mnswpr.js`) | Moves to |
+|---|---|
+| `document.createElement` grid build | client **Renderer** |
+| `data-status` / `data-value` / `game-status` attrs | core **State** (`Cell`, `phase`) |
+| `getStatus`/`setStatus`/`isMine`/`isFlagged` | core model ops |
+| `minesArray` + `transferMine` (first-click safety) | `minesweeper/board.js` (seeded gen) |
+| `handleEmpty` flood-fill, chording | `minesweeper/reveal.js` |
+| mouse/touch handlers, chording, long-press | client **InputAdapter** (emits Moves) |
+| `TimerService` (`Date.now`, rAF, DOM write) | clock → `GameSession`; display → `TimerView` |
+| `hooks.gameDone(game)` | terminal Event → Local builds `game` / Remote = server |
+| `levels.js` | `minesweeper/levels.js` |
+
+---
+
+## 9. Migration plan (each step keeps the suite green)
+
+1. **Core, headless & tested.** Port board gen, flood-fill, chording, win/loss
+   into `core/` as pure functions with unit tests over plain data (fast, no
+   DOM). Add seeded RNG + `replay()`. **← this diff.**
+2. **Renderer + LocalTransport.** Build the event-driven Renderer that reproduces
+   today's exact DOM, and `LocalTransport` around `GameSession`.
+3. **Port InputAdapter** to emit `Move`s into the transport instead of mutating
+   the DOM.
+4. **Swap `apps/mnswpr/main.js`** to construct the client with `LocalTransport`.
+   Behavior is identical to today — the existing jsdom tests (real DOM events on
+   `#app`) are the regression harness and must stay green.
+5. **(Later) Remote.** Add a host runtime running `GameSession` authoritatively
+   + `RemoteTransport`; the host records results.
+6. **(Later) Extract** `grid/` + `session/` into `@cozy-games/grid` +
+   `@cozy-games/game-session` once Sudoku exists.
+
+## 10. Testing strategy
+
+- **Core:** pure data-model unit tests — deterministic via fixed seeds; property
+  tests (e.g. flood-fill never reveals a mine; win ⇔ all non-mines revealed).
+- **Replay:** generate a random valid game, feed its log to `replay()`, assert
+  `valid` and matching time; mutate the log and assert rejection.
+- **Client:** keep the current jsdom tests (mount, dispatch real mouse events,
+  assert on cell/grid attributes) — now exercising Renderer + InputAdapter +
+  LocalTransport end-to-end.
+- **Determinism guard:** a lint/test that fails if `Date`/`Math.random` appear in
+  `core/` outside the injected `clock`/`rng` seams.
+
+## 11. Open decisions
+
+- **Package boundary:** ✅ *resolved* — one `@cozy-games/mnswpr` package, core at the
+  `./core` sub-path (§1). Extraction to `@cozy-games/grid` + `@cozy-games/game-session`
+  deferred to when Sudoku lands; the sub-path stays stable across that move.
+- **Host mode (replay-validation vs live authority):** *deferred.* Ship
+  offline-only for now (`LocalTransport`, client-owned timing — matches today's UX).
+  The deterministic core + `replay()` are built now so either path is a later
+  add-on, not a rewrite.
+- **Remote transport / server host / latency & cost:** *deferred* (offline-first).
+  HTTP-vs-WebSocket, Netlify Function vs Worker, and the session store are picked
+  when we do the server; the `Transport` interface reserves the seam.

packages/mnswpr/mnswpr.js

@@ -6,30 +6,39 @@
 import './mnswpr.css'
 
 import {
-  LoggerService,
   StorageService,
   TimerService
-} from '../utils/index.js'
+} from '@cozy-games/utils'
 import { levels } from './levels.js'
+import { MinesweeperRules } from './core/index.js'
+import { LocalTransport } from './client/transport.js'
+import { renderEvents, revealBoard } from './client/renderer.js'
 
 const TEST_MODE = false // set to true if you want to test the game with visual hints
 const MOBILE_BUSY_DELAY = 250
 const PC_BUSY_DELAY = 500
 
 /**
- * Create Minesweeper game board
+ * Create Minesweeper game board.
+ *
+ * This is the DOM CLIENT: it builds the board, handles input, and renders. All
+ * game state and rules live in the headless core (`./core`); the client drives
+ * it through a Transport and paints the events it emits (see
+ * docs/headless-core-and-client-design.md).
+ *
  * @param {String} appId
  * @param {String} version
  * @param {{
  * levelChanged: (setting: any) => void,
  * gameDone: (game: any) => void
  * } | undefined } hooks
+ * @param {{ seed?: number }} [options] - `seed` pins the (deterministic) board,
+ *   mainly for tests/replay; omit for a fresh random game each time.
  */
-const Minesweeper = function(appId, version, hooks = undefined) {
+const Minesweeper = function(appId, version, hooks = undefined, options = {}) {
   const _this = this
   const storageService = new StorageService()
   const timerService = new TimerService()
-  const loggerService = new LoggerService()
 
   if (!hooks) {
     hooks = {
@@ -38,6 +47,8 @@ const Minesweeper = function(appId, version, hooks = undefined) {
     }
   }
 
+  const configuredSeed = options.seed
+
   let grid = document.createElement('table')
   grid.setAttribute('id', 'grid')
   let flagsDisplay = document.createElement('span')
@@ -66,7 +77,6 @@ const Minesweeper = function(appId, version, hooks = undefined) {
     highlightSurroundingCell, // middle-click down
     rightClickCell // right-click down
   ]
-  let firstClick = true
   let isBusy = false
   let clickedCell
   let cachedSetting = storageService.getFromLocal('setting')
@@ -82,12 +92,10 @@ const Minesweeper = function(appId, version, hooks = undefined) {
   }
   storageService.saveToLocal('setting', setting)
   let flagsCount = setting.mines
-  // Mine positions stored as a Set of numeric keys (row * cols + col) for O(1) lookup
-  let mines = new Set()
   // Cells currently highlighted, so removeHighlights only resets these (<=9) instead of the whole grid
   let highlightedCells = []
-  // Count of safe (non-mine) cells revealed, so the win check is O(1) instead of scanning the whole grid
+  // The headless game for the current board; recreated on every generateGrid.
-  let revealedSafeCount = 0
+  let transport
 
   this.initialize = function() {
     const headingElement = document.createElement('h1')
@@ -129,8 +137,6 @@ const Minesweeper = function(appId, version, hooks = undefined) {
       levelsDropdown.add(levelOption, null)
     })
 
-    
-
     if (TEST_MODE) {
       const testLevel = document.createElement('span')
       testLevel.innerText = 'Test Mode'
@@ -144,24 +150,20 @@ const Minesweeper = function(appId, version, hooks = undefined) {
 
   function initializeToolbar() {
     const toolbar = document.createElement('div')
-    const toolbarItems = []
 
     const flagsWrapper = document.createElement('div')
     flagsWrapper.append(flagsDisplay)
     flagsWrapper.style.height = '20px'
     toolbar.append(flagsWrapper)
-    toolbarItems.push(flagsWrapper)
 
     const smileyWrapper = document.createElement('div')
     smileyWrapper.append(smileyDisplay)
     // toolbar.append(smileyWrapper);
-    // toolbarItems.push(smileyWrapper);
 
     const timerWrapper = document.createElement('div')
     timerWrapper.append(timerDisplay)
     timerWrapper.style.height = '20px'
     toolbar.append(timerWrapper)
-    toolbarItems.push(timerWrapper)
 
     toolbar.style.cursor = 'pointer'
     toolbar.style.padding = '10px 35px'
@@ -182,7 +184,6 @@ const Minesweeper = function(appId, version, hooks = undefined) {
     generateGrid({ initial: true })
   }
 
-
   /**
    * Generate the Game Board
    * @param {{
@@ -190,13 +191,10 @@ const Minesweeper = function(appId, version, hooks = undefined) {
    * }} options - Game Board Options
    */
   function generateGrid(options = { initial: false }) {
-    firstClick = true
     grid.innerHTML = ''
     grid.oncontextmenu = () => false
     flagsCount = setting.mines
-    mines.clear()
     highlightedCells = []
-    revealedSafeCount = 0
 
     for (let i = 0; i < setting.rows; i++) {
       let row = grid.insertRow(i)
@@ -224,6 +222,12 @@ const Minesweeper = function(appId, version, hooks = undefined) {
       appElement.style.margin = '0 auto'
     }
 
+    // A fresh headless game. Mines are placed by the core on the first reveal
+    // (first-click safe), so there is nothing to seed into the DOM here.
+    const gameSeed = configuredSeed !== undefined ? configuredSeed : Math.floor(Math.random() * 0x7fffffff)
+    transport = new LocalTransport(MinesweeperRules, { seed: gameSeed, config: setting, clock: () => Date.now() })
+    transport.onEvent(onCoreEvent)
+
     /**
      * TODO: add hook afterGridGenerated
      *   - for initializing the leaderboard
@@ -233,8 +237,51 @@ const Minesweeper = function(appId, version, hooks = undefined) {
 
     timerService.initialize(timerDisplay)
     updateFlagsCountDisplay()
-    addMines(setting.mines)
+  }
 
+  /**
+   * Paint the events from a core move, and drive the win/loss transition. Fired
+   * synchronously by the LocalTransport; a RemoteTransport would fire it on the
+   * server's reply with no change here.
+   * @param {{ events: object[], view: object }} payload
+   */
+  function onCoreEvent(payload) {
+    renderEvents(grid, payload.events)
+    for (const ev of payload.events) {
+      if (ev.type === 'explode' || ev.type === 'win') {
+        finishGame(payload.view)
+        break
+      }
+    }
+  }
+
+  /** Terminal transition: reveal the board, update displays, fire gameDone. */
+  function finishGame(view) {
+    const won = view.phase === 'won'
+    if (won) {
+      grid.setAttribute('game-status', 'win')
+      updateFlagsCountDisplay(0)
+    } else {
+      flagsDisplay.innerHTML = '&#128561;'
+      grid.setAttribute('game-status', 'over')
+    }
+    revealBoard(grid, view, setting)
+    grid.setAttribute('game-status', 'done')
+
+    const time = timerService.stop()
+    const game = {
+      time,
+      status: won ? 'win' : 'loss',
+      level: setting.id,
+      time_stamp: new Date(),
+      isMobile
+    }
+
+    /**
+     * TODO: add hook after gameSession send back `game`
+     *   - for sending the game score to the db
+     */
+    hooks.gameDone(game)
   }
 
   function setBusy() {
@@ -403,11 +450,6 @@ const Minesweeper = function(appId, version, hooks = undefined) {
     cell.onmousemove = function(e) {
       if ((pressed || bothPressed) && typeof e === 'object') {
         removeHighlights()
-        /*
-                if (!isEqual(clickedCell, cell)) {
-                    clickedCell = undefined;
-                }
-                */
         if (pressed == 'middle' || (isLeft && isRight)) {
           highlightSurroundingCell(this)
         } else if (pressed == 'left') {
@@ -456,187 +498,6 @@ const Minesweeper = function(appId, version, hooks = undefined) {
     skip = true
   }
 
-  function addMines(minesCount) {
-    //Add mines randomly
-    for (let i=0; i<minesCount; i++) {
-      let row = Math.floor(Math.random() * setting.rows)
-      let col = Math.floor(Math.random() * setting.cols)
-      let cell = grid.rows[row].cells[col]
-      if (isMine(cell)) {
-        transferMine()
-      } else {
-        mines.add(mineKey(row, col))
-      }
-      if (TEST_MODE){
-        cell.innerHTML = 'X'
-      }
-    }
-    if (TEST_MODE) {
-      printMines()
-    }
-  }
-
-  function revealMines() {
-    if (grid.getAttribute('game-status') == 'done') return
-    //Highlight all mines in red
-    const win = grid.getAttribute('game-status') == 'win'
-    for (let i=0; i<setting.rows; i++) {
-      for(let j=0; j<setting.cols; j++) {
-        let cell = grid.rows[i].cells[j]
-        if (win) {
-          handleWinRevelation(cell)
-        } else {
-          handleLostRevelation(cell)
-        }
-      }
-    }
-    grid.setAttribute('game-status', 'done')
-
-    const time = timerService.stop()
-    const game = {
-      time,
-      status: win ? 'win' : 'loss',
-      level: setting.id,
-      time_stamp: new Date(),
-      isMobile
-    }
-
-    /**
-     * TODO: add hook after gameSession send back `game`
-     *   - for sending the game score to the db
-     */
-    hooks.gameDone(game)
-
-  }
-
-  function handleWinRevelation(cell) {
-    updateFlagsCountDisplay(0)
-    if (isMine(cell)) {
-      cell.innerHTML = ':)'
-      cell.className = 'correct'
-      setStatus(cell, 'clicked')
-      let correct = document.createAttribute('title')
-      correct.value = 'Correct'
-      cell.setAttributeNode(correct)
-      setStatus(cell, 'clicked')
-    }
-  }
-
-  function handleLostRevelation(cell) {
-    if (isFlagged(cell)) {
-      cell.className = 'flag'
-      if (!isMine(cell)) {
-        cell.innerHTML = 'X'
-        cell.className = 'wrong'
-        let wrong = document.createAttribute('title')
-        wrong.value = 'Wrong'
-        cell.setAttributeNode(wrong)
-      } else {
-        cell.innerHTML = ':)'
-        cell.className = 'correct'
-        let correct = document.createAttribute('title')
-        correct.value = 'Correct'
-        cell.setAttributeNode(correct)
-      }
-    } else {
-      if (isMine(cell)) {
-        cell.className = 'mine'
-        setStatus(cell, 'clicked')
-      }
-    }
-  }
-
-  function isOpen(cell) {
-    return cell.innerHTML !== '' && !isFlagged(cell)
-  }
-
-  function isFlagged(cell) {
-    return getStatus(cell) == 'flagged'
-  }
-
-  function mineKey(row, col) {
-    return row * setting.cols + col
-  }
-
-  function isMine(cell) {
-    return mines.has(mineKey(getRow(cell), getCol(cell)))
-  }
-
-  function checkLevelCompletion() {
-    const safeCells = setting.rows * setting.cols - setting.mines
-    if (revealedSafeCount >= safeCells && grid.getAttribute('game-status') == 'active') {
-      grid.setAttribute('game-status', 'win')
-      revealMines()
-    }
-  }
-
-  function setStatus(cell, status) {
-    cell.setAttribute('data-status', status)
-  }
-
-  function getCol(cell) {
-    return cell.cellIndex
-  }
-
-  function getRow(cell) {
-    return cell.parentNode.rowIndex
-  }
-
-  function getStatus(cell) {
-    if (!cell) return undefined
-    return cell.getAttribute('data-status')
-  }
-
-  function middleClickCell(cell) {
-    if (grid.getAttribute('game-status') != 'active' || getStatus(cell) !== 'clicked') {
-      return
-    }
-    // check for number of surrounding flags
-    const valueString = cell.getAttribute('data-value')
-    let cellValue = parseInt(valueString, 10)
-    let flagCount = countFlagsAround(cell)
-
-    if (flagCount === cellValue) {
-      clickSurrounding(cell)
-      if (TEST_MODE) loggerService.debug('middle click', cell)
-    }
-  }
-
-  function countFlagsAround(cell) {
-    let flagCount = 0
-    let cellRow = cell.parentNode.rowIndex
-    let cellCol = cell.cellIndex
-    for (let i = Math.max(cellRow-1,0); i <= Math.min(cellRow+1, setting.rows - 1); i++) {
-      for(let j = Math.max(cellCol-1,0); j <= Math.min(cellCol+1, setting.cols - 1); j++) {
-        if (isFlagged(grid.rows[i].cells[j])) flagCount++
-      }
-    }
-    return flagCount
-  }
-
-  function clickSurrounding(cell) {
-    if (grid.getAttribute('game-status') != 'active') return
-    let cellRow = cell.parentNode.rowIndex
-    let cellCol = cell.cellIndex
-    for (let i = Math.max(cellRow-1,0); i <= Math.min(cellRow+1, setting.rows - 1); i++) {
-      for(let j = Math.max(cellCol-1,0); j <= Math.min(cellCol+1, setting.cols - 1); j++) {
-        let currentCell = grid.rows[i].cells[j]
-        if (getStatus(currentCell) == 'flagged') continue
-        openCell(currentCell)
-      }
-    }
-  }
-
-  function increaseFlagsCount() {
-    flagsCount++
-    updateFlagsCountDisplay()
-  }
-
-  function decreaseFlagsCount() {
-    flagsCount--
-    updateFlagsCountDisplay()
-  }
-
   function activateGame() {
     grid.setAttribute('game-status', 'active')
     // start timer
@@ -659,7 +520,7 @@ const Minesweeper = function(appId, version, hooks = undefined) {
   function highlightCell(cell) {
     if (isFlagged(cell)) return
     if (!gameIsDone() && getStatus(cell) == 'default') {
-      setStatus(cell, 'highlighted') // currentCell.classList.add('highlight');
+      setStatus(cell, 'highlighted')
       highlightedCells.push(cell)
     }
   }
@@ -677,28 +538,61 @@ const Minesweeper = function(appId, version, hooks = undefined) {
     }
   }
 
+  function increaseFlagsCount() {
+    flagsCount++
+    updateFlagsCountDisplay()
+  }
+
+  function decreaseFlagsCount() {
+    flagsCount--
+    updateFlagsCountDisplay()
+  }
+
+  function isFlagged(cell) {
+    return getStatus(cell) == 'flagged'
+  }
+
+  function setStatus(cell, status) {
+    cell.setAttribute('data-status', status)
+  }
+
+  function getCol(cell) {
+    return cell.cellIndex
+  }
+
+  function getRow(cell) {
+    return cell.parentNode.rowIndex
+  }
+
+  function getStatus(cell) {
+    if (!cell) return undefined
+    return cell.getAttribute('data-status')
+  }
+
+  // ---- input → core move adapters ----
+
   function rightClickCell(cell) {
     if (isFlagged(cell)) setBusy()
     if (grid.getAttribute('game-status') == 'inactive') {
       activateGame()
     }
     if (grid.getAttribute('game-status') != 'active') return
-    if (getStatus(cell) != 'clicked' && getStatus(cell) != 'empty') {
+
-      if (getStatus(cell) == 'default' || getStatus(cell) == 'highlighted') {
+    const status = getStatus(cell)
+    if (status == 'clicked' || status == 'empty') return
+
+    const move = { type: 'flag', r: getRow(cell), c: getCol(cell) }
+    if (status == 'default' || status == 'highlighted') {
       if (flagsCount <= 0) return
-        cell.className = 'flag'
+      transport.send(move) // renderer paints the flag
       decreaseFlagsCount()
-        setStatus(cell, 'flagged')
     } else {
-        cell.className = ''
+      transport.send(move) // toggles the flag off
       increaseFlagsCount()
-        setStatus(cell, 'default')
     }
     if ('vibrate' in navigator) {
       navigator.vibrate(100)
     }
-      if (TEST_MODE) loggerService.debug('right click', cell)
-    }
   }
 
   function clickCell(cell) {
@@ -707,164 +601,26 @@ const Minesweeper = function(appId, version, hooks = undefined) {
       activateGame()
     }
     if (grid.getAttribute('game-status') != 'active') return
-    //Check if the end-user clicked on a mine
+    if (isFlagged(cell) || grid.getAttribute('game-status') == 'over') {
-    if (TEST_MODE) loggerService.debug('click', cell)
-    if (getStatus(cell) == 'flagged' || grid.getAttribute('game-status') == 'over') {
-      return
-    } else if (getStatus(cell) == 'clicked') {
-      middleClickCell(cell)
-      return
-    } else if (isMine(cell) && firstClick) {
-      // cell.setAttribute('data-mine', 'false');
-      mines.delete(mineKey(getRow(cell), getCol(cell)))
-      transferMine(cell)
-      if (TEST_MODE) printMines()
-    }
-
-    openCell(cell)
-  }
-
-  function printMines() {
-    let count = 0
-    for (let i = 0; i < setting.rows; i++) {
-      for (let j = 0; j < setting.cols; j++) {
-        if (isMine(grid.rows[i].cells[j])) {
-          loggerService.debug(count++ + ' - mine: [' + i + ',' + j + ']')
-        }
-      }
-    }
-  }
-
-  function transferMine(cell = undefined) {
-    let found = false
-    do {
-      let row = Math.floor(Math.random() * setting.rows)
-      let col = Math.floor(Math.random() * setting.cols)
-      const transferMineToCell = grid.rows[row].cells[col]
-      if (isMine(transferMineToCell) || transferMineToCell === cell || isNeighbor(cell, transferMineToCell)) {
-        continue
-      } else {
-        mines.add(mineKey(row, col))
-        if (TEST_MODE){
-          transferMineToCell.innerHTML = 'X'
-          if (TEST_MODE) loggerService.debug('transferred mine to: ' + row + ', ' + col)
-        }
-        // TODO: refactor maybe
-        // eslint-disable-next-line no-useless-assignment
-        found = true
-        return
-      }
-    } while(!found)
-  }
-
-  function isNeighbor(cell, nextCell) {
-    if (cell === undefined) {
-      return
-    }
-    const rowDifference = Math.abs(getRow(cell) - getRow(nextCell))
-    const colDifference = Math.abs(getCol(cell) - getCol(nextCell))
-
-    return (rowDifference === 1) && (colDifference === 1)
-  }
-
-  function countMinesAround(cell) {
-    let mineCount=0
-    let cellRow = cell.parentNode.rowIndex
-    let cellCol = cell.cellIndex
-    for (let i = Math.max(cellRow-1,0); i <= Math.min(cellRow+1,setting.rows-1); i++) {
-      const rows = grid.rows[i]
-      if (!rows) continue
-      for(let j = Math.max(cellCol-1,0); j <= Math.min(cellCol+1,setting.cols-1); j++) {
-        const cell = rows.cells[j] 
-        const mine = isMine(cell)
-        if (cell && mine) {
-          mineCount++
-        }
-      }
-    }
-    return mineCount
-  }
-
-  function updateCellValue(cell, value) {
-    const spanElement = document.createElement('span')
-    spanElement.innerHTML = value
-    cell.innerHTML = ''
-    cell.appendChild(spanElement)
-  }
-
-  /**
-   * Reveal a single known-non-mine cell. Returns true when the cell is blank
-   * (no adjacent mines), which is the signal to keep flooding from it.
-   * @param {HTMLTableCellElement} cell
-   */
-  function revealSafeCell(cell) {
-    // A cell can be re-opened via chording, so only count the first reveal
-    const wasOpen = getStatus(cell) == 'clicked' || getStatus(cell) == 'empty'
-    cell.className = 'clicked'
-    setStatus(cell, 'clicked')
-    if (!wasOpen) revealedSafeCount++
-
-    const mineCount = countMinesAround(cell)
-    if (mineCount == 0) {
-      updateCellValue(cell, ' ')
-      setStatus(cell, 'empty')
-      return true
-    }
-
-    updateCellValue(cell, mineCount.toString())
-    const dataValue = document.createAttribute('data-value')
-    dataValue.value = mineCount.toString()
-    cell.setAttributeNode(dataValue)
-    return false
-  }
-
-  /**
-   * Iteratively reveal the connected region of blank cells, starting from a
-   * cell that has already been revealed as blank. Uses an explicit queue with
-   * isOpen() as the visited guard instead of recursing back through clickCell,
-   * so there are no redundant per-cell checks and no deep call stack.
-   * @param {HTMLTableCellElement} startCell
-   */
-  function handleEmpty(startCell) {
-    const queue = [startCell]
-    while (queue.length) {
-      const cell = queue.shift()
-      const cellRow = cell.parentNode.rowIndex
-      const cellCol = cell.cellIndex
-      for (let i = Math.max(cellRow-1,0); i <= Math.min(cellRow+1, setting.rows - 1); i++) {
-        const rows = grid.rows[i]
-        if (!rows) continue
-        for (let j = Math.max(cellCol-1,0); j <= Math.min(cellCol+1, setting.cols - 1); j++) {
-          const neighbor = rows.cells[j]
-          if (!neighbor || neighbor === cell) continue
-          if (isFlagged(neighbor)) {
-            setBusy()
-            continue
-          }
-          if (isOpen(neighbor)) continue
-          // blank cells have no adjacent mines, so every neighbor here is safe
-          if (revealSafeCell(neighbor)) queue.push(neighbor)
-        }
-      }
-    }
-  }
-
-  function openCell(cell) {
-    if (grid.getAttribute('game-status') != 'active') return
-
-    firstClick = false
-
-    if (isMine(cell)) {
-      cell.className = 'clicked'
-      setStatus(cell, 'clicked')
-      revealMines()
-      flagsDisplay.innerHTML = '&#128561;'
-      grid.setAttribute('game-status', 'over')
       return
     }
 
-    if (revealSafeCell(cell)) handleEmpty(cell)
+    const r = getRow(cell)
-    checkLevelCompletion()
+    const c = getCol(cell)
+    // An already-open number chords; anything else is a reveal. The core places
+    // mines on the first reveal (first-click safe), so no transfer is needed.
+    if (getStatus(cell) == 'clicked') {
+      transport.send({ type: 'chord', r, c })
+      return
+    }
+    transport.send({ type: 'reveal', r, c })
+  }
+
+  function middleClickCell(cell) {
+    if (grid.getAttribute('game-status') != 'active' || getStatus(cell) !== 'clicked') {
+      return
+    }
+    transport.send({ type: 'chord', r: getRow(cell), c: getCol(cell) })
   }
 }
 

packages/mnswpr/package.json

@@ -1,5 +1,5 @@
 {
-  "name": "@ayo-run/mnswpr",
+  "name": "@cozy-games/mnswpr",
   "version": "0.4.36",
   "description": "Classic Minesweeper browser game",
   "author": "Ayo",
@@ -10,13 +10,20 @@
   },
   "homepage": "https://mnswpr.com",
   "scripts": {
-    "release": "bumpp && node ../scripts/release.js"
+    "build": "vite build",
+    "release": "bumpp && node ../../scripts/release.js"
   },
   "main": "mnswpr.js",
+  "devDependencies": {
+    "@cozy-games/utils": "workspace:*"
+  },
   "exports": {
     ".": {
       "default": "./dist/mnswpr.js"
     },
+    "./core": {
+      "default": "./core/index.js"
+    },
     "./dist/*": {
       "default": "./dist/*"
     },

packages/mnswpr/test/core.test.js

@@ -0,0 +1,788 @@
+import { describe, it, expect } from 'vitest'
+import { readFileSync, readdirSync, statSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { dirname, join } from 'node:path'
+
+import {
+  Grid, eightWay, orthogonal,
+  GameSession, replay, mulberry32,
+  MinesweeperRules, generateBoard, validateLayout, MOVE_EVENT_TYPES, levels
+} from '../core/index.js'
+import { placeMines, excludeAround } from '../core/minesweeper/board.js'
+
+const beginner = levels.beginner
+
+// Reveal every non-mine cell of a session's board, reading the (already-placed)
+// state — a deterministic way to drive a game to a win without hardcoding the
+// layout. Returns the events for assertions.
+function playToWin(session, clock) {
+  // First reveal seeds the board (first-click safe); pick a corner.
+  session.applyMove({ type: 'reveal', r: 0, c: 0 })
+  const { grid, config } = session.state
+  for (let r = 0; r < config.rows; r++) {
+    for (let c = 0; c < config.cols; c++) {
+      if (!grid.at(r, c).mine && grid.at(r, c).status !== 'revealed') {
+        if (clock) clock.tick()
+        session.applyMove({ type: 'reveal', r, c })
+      }
+    }
+  }
+}
+
+describe('grid + neighbors (Layer 0)', () => {
+  it('addresses cells and reports bounds', () => {
+    const g = new Grid(3, 4, (r, c) => `${r},${c}`)
+    expect(g.rows).toBe(3)
+    expect(g.cols).toBe(4)
+    expect(g.at(2, 3)).toBe('2,3')
+    expect(g.inBounds(2, 3)).toBe(true)
+    expect(g.inBounds(3, 0)).toBe(false)
+    expect(g.inBounds(-1, 0)).toBe(false)
+  })
+
+  it('eightWay yields 8 neighbors interior, 3 in a corner', () => {
+    const g = new Grid(5, 5)
+    expect(eightWay(g, 2, 2)).toHaveLength(8)
+    expect(eightWay(g, 0, 0)).toHaveLength(3)
+    expect(orthogonal(g, 2, 2)).toHaveLength(4)
+    expect(orthogonal(g, 0, 0)).toHaveLength(2)
+  })
+})
+
+describe('rng (Layer 1)', () => {
+  it('is deterministic for a given seed', () => {
+    const a = mulberry32(12345)
+    const b = mulberry32(12345)
+    const seqA = [a(), a(), a()]
+    const seqB = [b(), b(), b()]
+    expect(seqA).toEqual(seqB)
+    expect(mulberry32(1)()).not.toBe(mulberry32(2)())
+  })
+})
+
+describe('board generation (Layer 2)', () => {
+  it('places exactly `mines` mines, deterministically from the seed', () => {
+    const mk = () => {
+      const g = new Grid(beginner.rows, beginner.cols, () => ({ mine: false, adjacent: 0, status: 'hidden' }))
+      const placed = placeMines(42, beginner, excludeAround(beginner, 0, 0), g)
+      return { g, placed }
+    }
+    const one = mk()
+    const two = mk()
+    expect(one.placed.size).toBe(beginner.mines)
+    expect([...one.placed].sort()).toEqual([...two.placed].sort())
+  })
+
+  it('keeps the first-click 3x3 neighborhood mine-free', () => {
+    const g = new Grid(beginner.rows, beginner.cols, () => ({ mine: false, adjacent: 0, status: 'hidden' }))
+    placeMines(7, beginner, excludeAround(beginner, 4, 4), g)
+    for (let dr = -1; dr <= 1; dr++) {
+      for (let dc = -1; dc <= 1; dc++) {
+        expect(g.at(4 + dr, 4 + dc).mine).toBe(false)
+      }
+    }
+  })
+
+  it('computes adjacency as the 8-way mine count', () => {
+    const g = new Grid(beginner.rows, beginner.cols, () => ({ mine: false, adjacent: 0, status: 'hidden' }))
+    placeMines(99, beginner, excludeAround(beginner, 0, 0), g)
+    g.forEach((cell, r, c) => {
+      if (cell.mine) return
+      let n = 0
+      for (const [nr, nc] of eightWay(g, r, c)) if (g.at(nr, nc).mine) n++
+      expect(cell.adjacent).toBe(n)
+    })
+  })
+})
+
+describe('generateBoard (Layer 2, pure)', () => {
+  it('is callable in plain Node and returns a plain layout object', () => {
+    // Non-square (rows ≠ cols) pins the rows-first orientation.
+    const layout = generateBoard(4, 7, 5, { seed: 42 })
+    expect(layout.rows).toBe(4)
+    expect(layout.cols).toBe(7)
+    expect(layout.mines).toBe(5)
+    expect(layout.cells).toHaveLength(4)
+    expect(layout.cells.every(row => row.length === 7)).toBe(true)
+    // plain data only — no Grid instance, no class methods leaking out
+    expect(layout.cells[0][0]).toEqual({ mine: expect.any(Boolean), adjacent: expect.any(Number) })
+    expect(layout).toEqual(JSON.parse(JSON.stringify(layout)))
+    // places exactly `mines` mines
+    expect(layout.mineLocations).toHaveLength(5)
+    let mineCount = 0
+    for (const row of layout.cells) for (const cell of row) if (cell.mine) mineCount++
+    expect(mineCount).toBe(5)
+  })
+
+  it('same injected RNG (seed) → identical layout', () => {
+    const a = generateBoard(16, 16, 40, { rng: mulberry32(123) })
+    const b = generateBoard(16, 16, 40, { rng: mulberry32(123) })
+    expect(a).toEqual(b)
+    // and the seed convenience wrapper matches an explicitly injected mulberry32
+    expect(generateBoard(16, 16, 40, { seed: 123 })).toEqual(a)
+    // a different seed diverges
+    expect(generateBoard(16, 16, 40, { seed: 124 })).not.toEqual(a)
+  })
+
+  it('computes adjacency as the 8-way mine count', () => {
+    const layout = generateBoard(9, 9, 10, { seed: 99 })
+    const g = new Grid(9, 9, (r, c) => layout.cells[r][c])
+    layout.cells.forEach((row, r) => row.forEach((cell, c) => {
+      if (cell.mine) return
+      let n = 0
+      for (const [nr, nc] of eightWay(g, r, c)) if (g.at(nr, nc).mine) n++
+      expect(cell.adjacent).toBe(n)
+    }))
+  })
+
+  it('honors an exclude set (e.g. first-click safety)', () => {
+    const exclude = new Set([0]) // key 0 == cell (0,0)
+    const layout = generateBoard(9, 9, 10, { seed: 7, exclude })
+    expect(layout.cells[0][0].mine).toBe(false)
+  })
+
+  it('rejects impossible dimensions and mine counts', () => {
+    expect(() => generateBoard(0, 9, 1)).toThrow(RangeError)
+    expect(() => generateBoard(3, 3, 10)).toThrow(RangeError) // more mines than cells
+    expect(() => generateBoard(3, 3, -1)).toThrow(RangeError)
+  })
+})
+
+describe('generateBoard first-move-safe (safeCell)', () => {
+  it('never mines the safe cell across randomized runs (property-style)', () => {
+    // Dense board so the safe cell is a demanding constraint, swept over many
+    // injected-RNG streams — the guarantee must hold for every seed, not one.
+    for (let seed = 0; seed < 200; seed++) {
+      const layout = generateBoard(9, 9, 70, { rng: mulberry32(seed), safeCell: { r: 4, c: 5 } })
+      expect(layout.cells[4][5].mine).toBe(false)
+      // and it's a genuine constraint on top of a correct board: exact mine count
+      expect(layout.mineLocations).toHaveLength(70)
+    }
+  })
+
+  it('holds at edge coordinates — every corner and a border cell', () => {
+    const corners = [{ r: 0, c: 0 }, { r: 0, c: 8 }, { r: 8, c: 0 }, { r: 8, c: 8 }]
+    const borders = [{ r: 0, c: 4 }, { r: 4, c: 0 }, { r: 8, c: 4 }, { r: 4, c: 8 }]
+    for (const safeCell of [...corners, ...borders]) {
+      const layout = generateBoard(9, 9, 70, { seed: 123, safeCell })
+      expect(layout.cells[safeCell.r][safeCell.c].mine).toBe(false)
+    }
+  })
+
+  it('generates a max-density board (mines = cells − 1) with the one safe cell blank', () => {
+    // 3x3 with 8 mines: every cell except the safe one must be a mine.
+    const layout = generateBoard(3, 3, 8, { seed: 5, safeCell: { r: 1, c: 1 } })
+    expect(layout.mineLocations).toHaveLength(8)
+    expect(layout.cells[1][1].mine).toBe(false)
+    let mines = 0
+    for (const row of layout.cells) for (const cell of row) if (cell.mine) mines++
+    expect(mines).toBe(8)
+  })
+
+  it('merges with an existing exclude set rather than replacing it', () => {
+    const exclude = new Set([0]) // key 0 == cell (0,0)
+    const layout = generateBoard(5, 5, 23, { seed: 9, exclude, safeCell: { r: 4, c: 4 } })
+    expect(layout.cells[0][0].mine).toBe(false) // from exclude
+    expect(layout.cells[4][4].mine).toBe(false) // from safeCell
+    expect(layout.mineLocations).toHaveLength(23) // 25 − 2 excluded
+  })
+
+  it('rejects configurations where the mines cannot fit with the safe cell excluded', () => {
+    // 3x3 = 9 cells, one reserved for safety ⇒ capacity 8; 9 mines can't fit.
+    expect(() => generateBoard(3, 3, 9, { safeCell: { r: 0, c: 0 } })).toThrow(RangeError)
+  })
+
+  it('rejects an out-of-bounds or non-integer safe cell', () => {
+    expect(() => generateBoard(9, 9, 10, { safeCell: { r: 9, c: 0 } })).toThrow(RangeError)
+    expect(() => generateBoard(9, 9, 10, { safeCell: { r: -1, c: 0 } })).toThrow(RangeError)
+    expect(() => generateBoard(9, 9, 10, { safeCell: { r: 0, c: 1.5 } })).toThrow(RangeError)
+  })
+})
+
+describe('rules (Layer 2)', () => {
+  it('first reveal is never a mine and opens a region', () => {
+    const s = MinesweeperRules.init(3, beginner)
+    const { state, events } = MinesweeperRules.apply(s, { type: 'reveal', r: 0, c: 0 })
+    expect(state.phase).toBe('active')
+    expect(state.grid.at(0, 0).mine).toBe(false)
+    expect(events[0].type).toBe('reveal')
+    // first click is inside a mine-free 3x3, so it's blank and floods
+    expect(events[0].cells.length).toBeGreaterThan(1)
+  })
+
+  it('revealing a mine loses and emits explode with all mines', () => {
+    const s = MinesweeperRules.init(5, beginner)
+    MinesweeperRules.apply(s, { type: 'reveal', r: 0, c: 0 })
+    const mine = firstMine(s.grid)
+    const { state, events } = MinesweeperRules.apply(s, { type: 'reveal', r: mine.r, c: mine.c })
+    expect(state.phase).toBe('lost')
+    expect(events[0].type).toBe('explode')
+    expect(events[0].mines.length).toBe(beginner.mines)
+  })
+
+  it('toggles flags and blocks revealing a flagged cell', () => {
+    let s = MinesweeperRules.init(1, beginner)
+    s = MinesweeperRules.apply(s, { type: 'reveal', r: 0, c: 0 }).state
+    const hidden = firstHidden(s.grid)
+    let r = MinesweeperRules.apply(s, { type: 'flag', r: hidden.r, c: hidden.c })
+    expect(r.events[0]).toMatchObject({ type: 'flag', flagged: true })
+    // revealing a flagged cell is a no-op
+    r = MinesweeperRules.apply(r.state, { type: 'reveal', r: hidden.r, c: hidden.c })
+    expect(r.events).toHaveLength(0)
+    expect(r.state.grid.at(hidden.r, hidden.c).status).toBe('flagged')
+  })
+
+  it('project never leaks an unrevealed mine mid-game, but reveals mines when over', () => {
+    const s = MinesweeperRules.init(8, beginner)
+    const active = MinesweeperRules.apply(s, { type: 'reveal', r: 0, c: 0 }).state
+    const view = MinesweeperRules.project(active)
+    for (const cell of view.cells) {
+      if (cell.status !== 'revealed') expect(cell.mine).not.toBe(true)
+    }
+    // now lose and re-project
+    const mine = firstMine(active.grid)
+    const lost = MinesweeperRules.apply(active, { type: 'reveal', r: mine.r, c: mine.c }).state
+    const overView = MinesweeperRules.project(lost)
+    expect(overView.cells.some(c => c.status === 'hidden' && c.mine === true)).toBe(true)
+  })
+})
+
+describe('board injection (fromLayout, Layer 2)', () => {
+  // A hand-built 3x3 with a single mine at (0,0). Adjacency: the mine's three
+  // neighbors (0,1),(1,0),(1,1) are 1; everything else is 0.
+  const knownLayout = () => ({
+    rows: 3,
+    cols: 3,
+    mines: 1,
+    cells: [
+      [{ mine: true, adjacent: 0 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+      [{ mine: false, adjacent: 1 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+      [{ mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }]
+    ],
+    mineLocations: [[0, 0]]
+  })
+
+  it('creates a game instance from an injected layout and scripts moves to known states', () => {
+    const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(knownLayout()) })
+    expect(session.status()).toBe('fresh')
+
+    // Reveal a numbered (non-zero) cell: it activates the game and reveals just
+    // itself, carrying the layout's adjacency — proof the injected board is live.
+    const first = session.applyMove({ type: 'reveal', r: 0, c: 1 })
+    expect(session.status()).toBe('active')
+    expect(first.events[0].cells).toEqual([{ r: 0, c: 1, adjacent: 1 }])
+
+    // Stepping on the injected mine loses and reports it (before any flood wins).
+    const boom = session.applyMove({ type: 'reveal', r: 0, c: 0 })
+    expect(session.status()).toBe('lost')
+    expect(boom.events[0]).toMatchObject({ type: 'explode', r: 0, c: 0 })
+    expect(boom.events[0].mines).toEqual([{ r: 0, c: 0 }])
+  })
+
+  it('a zero cell floods the connected safe region on an injected board', () => {
+    const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(knownLayout()) })
+    // (2,2) is a zero far from the mine; flood opens all 8 safe cells → win.
+    const flood = session.applyMove({ type: 'reveal', r: 2, c: 2 })
+    expect(flood.events[0].cells.length).toBe(8)
+    expect(session.status()).toBe('won')
+  })
+
+  it('an injected board can be played to a win, every safe cell revealed', () => {
+    const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(knownLayout()) })
+    // Reveal all 8 non-mine cells; avoid (0,0).
+    for (let r = 0; r < 3; r++) {
+      for (let c = 0; c < 3; c++) {
+        if (r === 0 && c === 0) continue
+        session.applyMove({ type: 'reveal', r, c })
+      }
+    }
+    expect(session.status()).toBe('won')
+  })
+
+  it('plays identically to a generated board: injecting a generated layout reproduces its play', () => {
+    // Generate a board, then inject that exact layout. Revealing any cell must
+    // report the layout's own adjacency, and mines must sit where the layout says.
+    const layout = generateBoard(9, 9, 10, { seed: 42, safeCell: { r: 4, c: 4 } })
+    const state = MinesweeperRules.fromLayout(layout)
+    const { events } = MinesweeperRules.apply(state, { type: 'reveal', r: 4, c: 4 })
+    expect(state.phase).toBe('active')
+    // (4,4) was forced safe; its revealed adjacency matches the layout.
+    const seen = events[0].cells.find(cell => cell.r === 4 && cell.c === 4)
+    expect(seen.adjacent).toBe(layout.cells[4][4].adjacent)
+    // The mines are exactly the layout's mines.
+    const mines = []
+    state.grid.forEach((cell, r, c) => { if (cell.mine) mines.push([r, c]) })
+    expect(mines.sort()).toEqual([...layout.mineLocations].sort())
+  })
+
+  it('two sessions from the same layout with the same script transition identically', () => {
+    const script = [{ type: 'reveal', r: 2, c: 2 }, { type: 'flag', r: 0, c: 0 }, { type: 'reveal', r: 0, c: 1 }]
+    const run = () => {
+      const s = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(knownLayout()) })
+      return script.map(m => s.applyMove(m).view)
+    }
+    expect(run()).toEqual(run())
+  })
+
+  it('rejects malformed layouts with a clear error', () => {
+    expect(() => MinesweeperRules.fromLayout(null)).toThrow(TypeError)
+    expect(() => MinesweeperRules.fromLayout('nope')).toThrow(TypeError)
+    // dimensions don't match the cells grid
+    expect(() => MinesweeperRules.fromLayout({ ...knownLayout(), rows: 4 })).toThrow(RangeError)
+    // mine count disagrees with the actual mined cells
+    expect(() => MinesweeperRules.fromLayout({ ...knownLayout(), mines: 2 })).toThrow(RangeError)
+    // a cell missing its shape
+    const badCells = knownLayout()
+    badCells.cells[1][1] = { mine: false } // no `adjacent`
+    expect(() => MinesweeperRules.fromLayout(badCells)).toThrow(TypeError)
+    // mineLocations pointing at a non-mined cell
+    const badLocs = knownLayout()
+    badLocs.mineLocations = [[2, 2]]
+    expect(() => MinesweeperRules.fromLayout(badLocs)).toThrow(RangeError)
+  })
+
+  it('validateLayout accepts a freshly generated board', () => {
+    expect(() => validateLayout(generateBoard(16, 16, 40, { seed: 3 }))).not.toThrow()
+  })
+
+  it('leaves existing seed-based construction unaffected', () => {
+    // No `state` supplied ⇒ the session still generates from seed/config as before.
+    const session = new GameSession(MinesweeperRules, { seed: 3, config: beginner })
+    const { events } = session.applyMove({ type: 'reveal', r: 0, c: 0 })
+    expect(session.status()).toBe('active')
+    expect(session.state.grid.at(0, 0).mine).toBe(false) // first-click safety intact
+    expect(events[0].cells.length).toBeGreaterThan(1)
+  })
+})
+
+describe('state serialization (serialize / deserialize)', () => {
+  // Drive a fresh session to a genuine MID-GAME state: opening flood + a flag on
+  // a mine (which stays flagged and never needs revealing to win). Returns the
+  // session, its clock, and the flagged mine's coordinates.
+  function midGame(seed = 21) {
+    const clock = makeClock()
+    const session = new GameSession(MinesweeperRules, { seed, config: beginner, clock })
+    clock.tick()
+    session.applyMove({ type: 'reveal', r: 0, c: 0 }) // opening flood → active
+    const mine = firstMine(session.state.grid)
+    clock.tick()
+    session.applyMove({ type: 'flag', r: mine.r, c: mine.c })
+    return { session, clock, mine }
+  }
+
+  it('round-trips a mid-game snapshot through JSON without loss', () => {
+    const { session } = midGame()
+    expect(session.status()).toBe('active') // genuinely mid-game, not fresh/finished
+
+    const snap = session.serialize()
+    const roundTripped = JSON.parse(JSON.stringify(snap))
+    expect(roundTripped).toEqual(snap) // JSON-safe: stringify → parse is lossless
+
+    // deserialize → re-serialize reproduces the exact snapshot
+    const revived = GameSession.deserialize(MinesweeperRules, roundTripped, { clock: makeClock() })
+    expect(revived.serialize()).toEqual(snap)
+  })
+
+  it('snapshot covers layout, revealed + flagged cells, and session/clock state', () => {
+    const { session, mine } = midGame()
+    const snap = session.serialize()
+
+    // board layout
+    expect(snap.state.grid.rows).toBe(beginner.rows)
+    expect(snap.state.grid.cols).toBe(beginner.cols)
+    expect(snap.state.grid.cells).toHaveLength(beginner.rows * beginner.cols)
+    expect(snap.state.grid.cells[0]).toEqual({ mine: expect.any(Boolean), adjacent: expect.any(Number), status: expect.any(String) })
+
+    // per-cell state: the flood left revealed cells, and our flagged mine is flagged
+    expect(snap.state.grid.cells.some(c => c.status === 'revealed')).toBe(true)
+    expect(snap.state.grid.cells[mine.r * beginner.cols + mine.c].status).toBe('flagged')
+
+    // session / clock state: timer started (t0 set), still running (tEnd null), log intact
+    expect(snap.t0).not.toBeNull()
+    expect(snap.tEnd).toBeNull()
+    expect(snap.log).toHaveLength(2)
+    expect(snap.log[0]).toEqual({ move: { type: 'reveal', r: 0, c: 0 }, t: expect.any(Number) })
+  })
+
+  it('a deserialized session resumes and plays identically to the original', () => {
+    const playToWin = (session, clock) => {
+      const { grid, config } = session.state
+      for (let r = 0; r < config.rows; r++) {
+        for (let c = 0; c < config.cols; c++) {
+          if (!grid.at(r, c).mine && grid.at(r, c).status !== 'revealed') {
+            clock.tick()
+            session.applyMove({ type: 'reveal', r, c })
+          }
+        }
+      }
+    }
+
+    const { session, clock } = midGame(33)
+    const snap = session.serialize()
+    // Revive on a clock continuing from the same instant, so timing stays aligned.
+    const reviveClock = makeClock(clock())
+    const revived = GameSession.deserialize(MinesweeperRules, JSON.parse(JSON.stringify(snap)), { clock: reviveClock })
+
+    playToWin(session, clock)
+    playToWin(revived, reviveClock)
+
+    expect(revived.status()).toBe(session.status())
+    expect(revived.status()).toBe('won')
+    expect(revived.view()).toEqual(session.view())
+    expect(revived.elapsed()).toBe(session.elapsed())
+    expect(revived.result()).toEqual(session.result())
+  })
+
+  it('rules.serialize / deserialize round-trips a state and revives a real Grid', () => {
+    const state = MinesweeperRules.init(7, beginner)
+    MinesweeperRules.apply(state, { type: 'reveal', r: 0, c: 0 })
+    const snap = MinesweeperRules.serialize(state)
+    const revived = MinesweeperRules.deserialize(JSON.parse(JSON.stringify(snap)))
+    expect(revived.grid).toBeInstanceOf(Grid) // not a plain object — a live Grid
+    expect(revived.grid.at(0, 0)).toEqual(state.grid.at(0, 0))
+    expect(MinesweeperRules.serialize(revived)).toEqual(snap)
+  })
+
+  it('serialize throws clearly when the rules lack a serializer', () => {
+    const bareRules = { init: () => ({}), apply: s => ({ state: s, events: [] }), status: () => 'fresh', project: s => s }
+    const session = new GameSession(bareRules, { state: {} })
+    expect(() => session.serialize()).toThrow(TypeError)
+  })
+})
+
+describe('resume from serialized state (Layer 1)', () => {
+  // Reveal every remaining non-mine cell in row-major order, ticking the injected
+  // clock before each move — a deterministic way to finish an in-progress board.
+  const finish = (session, clock) => {
+    const { grid, config } = session.state
+    for (let r = 0; r < config.rows; r++) {
+      for (let c = 0; c < config.cols; c++) {
+        if (!grid.at(r, c).mine && grid.at(r, c).status !== 'revealed') {
+          clock.tick()
+          session.applyMove({ type: 'reveal', r, c })
+        }
+      }
+    }
+  }
+
+  const validSnapshot = () => {
+    const s = new GameSession(MinesweeperRules, { seed: 1, config: beginner, clock: makeClock() })
+    s.applyMove({ type: 'reveal', r: 0, c: 0 })
+    return JSON.parse(JSON.stringify(s.serialize()))
+  }
+
+  it('play N moves → serialize → restore → finish: final state identical to an uninterrupted run', () => {
+    // Uninterrupted reference run.
+    const clockU = makeClock()
+    const uninterrupted = new GameSession(MinesweeperRules, { seed: 77, config: beginner, clock: clockU })
+    clockU.tick()
+    uninterrupted.applyMove({ type: 'reveal', r: 0, c: 0 })
+    finish(uninterrupted, clockU)
+
+    // Interrupted: identical opening move, snapshot, restore on the SAME clock
+    // instant, then finish with the identical remaining moves.
+    const clockI = makeClock()
+    const before = new GameSession(MinesweeperRules, { seed: 77, config: beginner, clock: clockI })
+    clockI.tick()
+    before.applyMove({ type: 'reveal', r: 0, c: 0 })
+    const snap = JSON.parse(JSON.stringify(before.serialize()))
+    const resumed = GameSession.deserialize(MinesweeperRules, snap, { clock: clockI })
+    finish(resumed, clockI)
+
+    expect(resumed.status()).toBe('won')
+    expect(resumed.view()).toEqual(uninterrupted.view())     // identical board + progress
+    expect(resumed.result()).toEqual(uninterrupted.result()) // identical log + time
+  })
+
+  it('elapsed time continues (not reset) after restore, on the injected clock', () => {
+    const clock = makeClock() // 1000
+    const s = new GameSession(MinesweeperRules, { seed: 21, config: beginner, clock })
+    clock.tick() // 1050
+    s.applyMove({ type: 'reveal', r: 0, c: 0 }) // t0 = 1050
+    clock.tick(); clock.tick() // 1150
+    expect(s.elapsed()).toBe(100) // 1150 − 1050
+
+    const snap = JSON.parse(JSON.stringify(s.serialize()))
+    // Resume on a fresh clock that continues from the same instant (1150).
+    const reviveClock = makeClock(clock())
+    const resumed = GameSession.deserialize(MinesweeperRules, snap, { clock: reviveClock })
+
+    // Preserved, not reset to zero.
+    expect(resumed.elapsed()).toBe(100)
+
+    // And it keeps advancing on the injected clock as play continues.
+    reviveClock.tick() // 1200
+    const mine = firstMine(resumed.state.grid)
+    resumed.applyMove({ type: 'flag', r: mine.r, c: mine.c })
+    expect(resumed.elapsed()).toBe(150) // 1200 − 1050
+    expect(resumed.elapsed()).toBeGreaterThan(100)
+  })
+
+  it('a finished (won/lost) session round-trips with its final elapsed frozen', () => {
+    const clock = makeClock()
+    const s = new GameSession(MinesweeperRules, { seed: 5, config: beginner, clock })
+    clock.tick()
+    s.applyMove({ type: 'reveal', r: 0, c: 0 })
+    finish(s, clock)
+    expect(s.status()).toBe('won')
+    const finalTime = s.elapsed()
+
+    const resumed = GameSession.deserialize(
+      MinesweeperRules,
+      JSON.parse(JSON.stringify(s.serialize())),
+      { clock: makeClock(999999) } // a wildly different clock must not change a frozen time
+    )
+    expect(resumed.status()).toBe('won')
+    expect(resumed.elapsed()).toBe(finalTime)
+  })
+
+  it('rejects invalid or corrupt snapshots with a clear error', () => {
+    const good = validSnapshot()
+    // envelope corruption (caught by GameSession.deserialize)
+    expect(() => GameSession.deserialize(MinesweeperRules, null)).toThrow(TypeError)
+    expect(() => GameSession.deserialize(MinesweeperRules, { ...good, log: 'nope' })).toThrow(TypeError)
+    expect(() => GameSession.deserialize(MinesweeperRules, { ...good, log: [{ move: {}, t: 'soon' }] })).toThrow(TypeError)
+    expect(() => GameSession.deserialize(MinesweeperRules, { ...good, t0: 'later' })).toThrow(TypeError)
+    // game-state corruption (delegated to rules.deserialize)
+    expect(() => GameSession.deserialize(MinesweeperRules, { ...good, state: null })).toThrow(TypeError)
+    expect(() => GameSession.deserialize(MinesweeperRules, { ...good, state: { ...good.state, phase: 'bogus' } })).toThrow(RangeError)
+    const truncated = { ...good, state: { ...good.state, grid: { ...good.state.grid, cells: good.state.grid.cells.slice(1) } } }
+    expect(() => GameSession.deserialize(MinesweeperRules, truncated)).toThrow(RangeError)
+  })
+
+  it('rules.deserialize rejects a malformed state snapshot directly', () => {
+    expect(() => MinesweeperRules.deserialize(null)).toThrow(TypeError)
+    expect(() => MinesweeperRules.deserialize({})).toThrow(TypeError) // missing config/grid
+    const good = validSnapshot().state
+    expect(() => MinesweeperRules.deserialize({ ...good, grid: { ...good.grid, rows: good.grid.rows + 1 } })).toThrow(RangeError)
+  })
+})
+
+describe('typed move-events (onMove)', () => {
+  // A 3x3 with a single mine at (0,0); adjacency computed for it. Lets us script
+  // exact coordinates and outcomes for a fully-asserted event stream.
+  const knownLayout = () => ({
+    rows: 3,
+    cols: 3,
+    mines: 1,
+    cells: [
+      [{ mine: true, adjacent: 0 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+      [{ mine: false, adjacent: 1 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+      [{ mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }]
+    ],
+    mineLocations: [[0, 0]]
+  })
+
+  const injected = clock =>
+    new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(knownLayout()), clock })
+
+  it('exports the move-event vocabulary', () => {
+    expect(MOVE_EVENT_TYPES).toEqual(['reveal', 'flag', 'unflag', 'chord'])
+  })
+
+  it('emits the full typed event stream for a scripted game (all four types + no-op)', () => {
+    const clock = makeClock()
+    const session = injected(clock)
+    const events = []
+    session.onMove(e => events.push(e))
+
+    clock.tick() // 1050
+    session.applyMove({ type: 'reveal', r: 0, c: 1 }) // number cell → reveals itself
+    clock.tick() // 1100
+    session.applyMove({ type: 'flag', r: 0, c: 0 })   // flag the mine
+    clock.tick() // 1150
+    session.applyMove({ type: 'flag', r: 0, c: 0 })   // toggle off → unflag
+    clock.tick() // 1200
+    session.applyMove({ type: 'flag', r: 0, c: 0 })   // flag again
+    clock.tick() // 1250
+    session.applyMove({ type: 'chord', r: 0, c: 1 })  // 1 adjacent flag == value → chord
+    clock.tick() // 1300
+    session.applyMove({ type: 'reveal', r: 0, c: 1 }) // already revealed → no-op, no event
+
+    expect(events).toEqual([
+      { type: 'reveal', r: 0, c: 1, t: 1050, seq: 1 },
+      { type: 'flag', r: 0, c: 0, t: 1100, seq: 2 },
+      { type: 'unflag', r: 0, c: 0, t: 1150, seq: 3 },
+      { type: 'flag', r: 0, c: 0, t: 1200, seq: 4 },
+      { type: 'chord', r: 0, c: 1, t: 1250, seq: 5 }
+    ])
+  })
+
+  it('timestamps come from the injected clock', () => {
+    const clock = makeClock(5000)
+    const session = injected(clock)
+    let event
+    session.onMove(e => { event = e })
+    clock.tick() // 5050
+    session.applyMove({ type: 'reveal', r: 2, c: 2 })
+    expect(event.t).toBe(5050)
+  })
+
+  it('onMove returns an unsubscribe that stops delivery', () => {
+    const session = injected(makeClock())
+    const events = []
+    const off = session.onMove(e => events.push(e))
+    session.applyMove({ type: 'flag', r: 0, c: 0 })
+    off()
+    session.applyMove({ type: 'flag', r: 0, c: 0 }) // unflag — not delivered
+    expect(events).toHaveLength(1)
+    expect(events[0].type).toBe('flag')
+  })
+
+  it('sequence numbers strictly increase across a resume (core-05)', () => {
+    const clock = makeClock()
+    const session = injected(clock)
+    const seqs = []
+    session.onMove(e => seqs.push(e.seq))
+    clock.tick(); session.applyMove({ type: 'reveal', r: 0, c: 1 }) // seq 1
+    clock.tick(); session.applyMove({ type: 'flag', r: 0, c: 0 })   // seq 2
+
+    // Serialize → resume; the counter must continue, not restart.
+    const snap = JSON.parse(JSON.stringify(session.serialize()))
+    expect(snap.seq).toBe(2)
+    const resumed = GameSession.deserialize(MinesweeperRules, snap, { clock: makeClock(clock()) })
+    const resumedSeqs = []
+    resumed.onMove(e => resumedSeqs.push(e.seq))
+    resumed.applyMove({ type: 'flag', r: 0, c: 0 }) // unflag → seq 3, not 1
+
+    expect(resumedSeqs).toEqual([3])
+    // strictly increasing over the whole session
+    const all = [...seqs, ...resumedSeqs]
+    expect(all).toEqual([...all].sort((a, b) => a - b))
+    expect(new Set(all).size).toBe(all.length) // no duplicates
+  })
+
+  it('a losing reveal still emits a reveal move-event', () => {
+    const clock = makeClock()
+    const session = injected(clock)
+    let event
+    session.onMove(e => { event = e })
+    clock.tick()
+    session.applyMove({ type: 'reveal', r: 0, c: 0 }) // steps on the mine
+    expect(session.status()).toBe('lost')
+    expect(event).toEqual({ type: 'reveal', r: 0, c: 0, t: 1050, seq: 1 })
+  })
+})
+
+describe('session + timing (Layer 1)', () => {
+  it('reports authoritative elapsed time from the injected clock', () => {
+    const clock = makeClock()
+    const session = new GameSession(MinesweeperRules, { seed: 21, config: beginner, clock })
+    expect(session.elapsed()).toBe(0) // no move yet
+    playToWin(session, clock)
+    expect(session.status()).toBe('won')
+    // time is (terminal tick − first tick), owned by the clock, not the client
+    expect(session.elapsed()).toBeGreaterThan(0)
+    const result = session.result()
+    expect(result.status).toBe('won')
+    expect(result.seed).toBe(21)
+  })
+})
+
+describe('replay verification (Layer 1)', () => {
+  it('accepts a genuine winning log and recomputes the same time', () => {
+    const clock = makeClock()
+    const session = new GameSession(MinesweeperRules, { seed: 33, config: beginner, clock })
+    playToWin(session, clock)
+    const submission = session.result()
+    const verdict = replay(MinesweeperRules, submission)
+    expect(verdict.valid).toBe(true)
+    expect(verdict.status).toBe('won')
+    expect(verdict.time).toBe(submission.time)
+  })
+
+  it('rejects a truncated (non-terminal) log', () => {
+    const clock = makeClock()
+    const session = new GameSession(MinesweeperRules, { seed: 33, config: beginner, clock })
+    playToWin(session, clock)
+    const submission = session.result()
+    const truncated = { ...submission, log: submission.log.slice(0, 2) }
+    const verdict = replay(MinesweeperRules, truncated)
+    expect(verdict.valid).toBe(false)
+    expect(verdict.reason).toMatch(/terminal/)
+  })
+
+  it('rejects non-monotonic timestamps', () => {
+    const clock = makeClock()
+    const session = new GameSession(MinesweeperRules, { seed: 33, config: beginner, clock })
+    playToWin(session, clock)
+    const submission = session.result()
+    const tampered = { ...submission, log: submission.log.map((e, i) => ({ ...e, t: i === 1 ? -5 : e.t })) }
+    const verdict = replay(MinesweeperRules, tampered)
+    expect(verdict.valid).toBe(false)
+    expect(verdict.reason).toMatch(/monotonic/)
+  })
+
+  it('is deterministic: same seed + same log ⇒ same board', () => {
+    const a = MinesweeperRules.init(777, beginner)
+    const b = MinesweeperRules.init(777, beginner)
+    MinesweeperRules.apply(a, { type: 'reveal', r: 2, c: 2 })
+    MinesweeperRules.apply(b, { type: 'reveal', r: 2, c: 2 })
+    const minesA = []
+    const minesB = []
+    a.grid.forEach((cell, r, c) => { if (cell.mine) minesA.push(r * beginner.cols + c) })
+    b.grid.forEach((cell, r, c) => { if (cell.mine) minesB.push(r * beginner.cols + c) })
+    expect(minesA).toEqual(minesB)
+  })
+})
+
+describe('determinism guard (invariant #4)', () => {
+  it('no Date/Math.random in core/ outside the rng seam', () => {
+    const coreDir = join(dirname(fileURLToPath(import.meta.url)), '..', 'core')
+    const offenders = []
+    walk(coreDir, file => {
+      if (!file.endsWith('.js')) return
+      // Scan code only — strip comments so prose that *names* these APIs
+      // (e.g. "uses Math.imul, not Math.random") isn't a false positive.
+      const code = readFileSync(file, 'utf8')
+        .replace(/\/\*[\s\S]*?\*\//g, '')
+        .replace(/\/\/.*$/gm, '')
+      if (/\bMath\.random\b/.test(code) || /\bDate\.now\b/.test(code) || /\bnew Date\b/.test(code)) {
+        offenders.push(file)
+      }
+    })
+    expect(offenders).toEqual([])
+  })
+
+  it('no DOM/rendering coupling in core/ (headless invariant)', () => {
+    const coreDir = join(dirname(fileURLToPath(import.meta.url)), '..', 'core')
+    const offenders = []
+    walk(coreDir, file => {
+      if (!file.endsWith('.js')) return
+      const code = readFileSync(file, 'utf8')
+        .replace(/\/\*[\s\S]*?\*\//g, '')
+        .replace(/\/\/.*$/gm, '')
+      if (/\b(document|window|navigator|localStorage|requestAnimationFrame)\b/.test(code) || /from ['"][^'"]*(client|renderer)/.test(code)) {
+        offenders.push(file)
+      }
+    })
+    expect(offenders).toEqual([])
+  })
+})
+
+// ---- helpers ----
+
+function makeClock(start = 1000) {
+  let t = start
+  return Object.assign(() => t, { tick() { t += 50 } })
+}
+
+function firstMine(grid) {
+  let found = null
+  grid.forEach((cell, r, c) => { if (!found && cell.mine) found = { r, c } })
+  return found
+}
+
+function firstHidden(grid) {
+  let found = null
+  grid.forEach((cell, r, c) => { if (!found && cell.status === 'hidden' && !cell.mine) found = { r, c } })
+  return found
+}
+
+function walk(dir, fn) {
+  for (const name of readdirSync(dir)) {
+    const p = join(dir, name)
+    if (statSync(p).isDirectory()) walk(p, fn)
+    else fn(p)
+  }
+}

packages/mnswpr/test/levels.test.js

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest'
-import { levels } from '../lib/levels.js'
+import { levels } from '../levels.js'
 
 describe('levels', () => {
   it('defines the four expected difficulty presets', () => {

packages/mnswpr/test/minesweeper.test.js

@@ -1,5 +1,20 @@
 import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest'
-import Minesweeper from '../lib/mnswpr.js'
+import Minesweeper from '../mnswpr.js'
+import { MinesweeperRules } from '../core/index.js'
+
+// Ask the (deterministic) core for a seed whose first-click-safe board places
+// the single mine at `targetCol`. Lets the DOM tests below pin a layout honestly
+// via the client's `seed` option, instead of hoping a Math.random value lands it.
+function findSeedForMine(setting, firstClick, targetCol) {
+  for (let seed = 1; seed < 100000; seed++) {
+    const state = MinesweeperRules.init(seed, setting)
+    MinesweeperRules.apply(state, { type: 'reveal', r: firstClick.r, c: firstClick.c })
+    let mineCol = -1
+    state.grid.forEach((cell, r, c) => { if (cell.mine) mineCol = c })
+    if (mineCol === targetCol) return seed
+  }
+  throw new Error('no seed found for target mine column')
+}
 
 // Build a fresh board mounted on #app and return its grid <table>.
 function mountGame() {
@@ -38,11 +53,12 @@ describe('Minesweeper board', () => {
     vi.restoreAllMocks()
   })
 
-  // Mount a game on a custom board injected via the cached 'setting' localStorage key.
+  // Mount a game on a custom board injected via the cached 'setting' localStorage
-  function mountCustomGame(setting, hooks) {
+  // key. `options.seed` pins the (deterministic) mine layout.
+  function mountCustomGame(setting, hooks, options) {
     localStorage.setItem('setting', JSON.stringify(setting))
     document.body.innerHTML = '<div id="app"></div>'
-    const game = new Minesweeper('app', 'dev', hooks)
+    const game = new Minesweeper('app', 'dev', hooks, options)
     game.initialize()
     return document.getElementById('grid')
   }
@@ -143,25 +159,27 @@ describe('Minesweeper board', () => {
   })
 
   it('does not declare a win until the last safe cell is revealed', () => {
-    // 1x3 board with the single mine pinned to the middle column.
+    // 1x3 board; pin the single mine to the middle column so neither end cascades.
-    vi.spyOn(Math, 'random').mockReturnValue(0.5)
+    const setting = { rows: 1, cols: 3, mines: 1, id: 'test', name: 'test' }
-    const grid = mountCustomGame({ rows: 1, cols: 3, mines: 1, id: 'test', name: 'test' })
+    const seed = findSeedForMine(setting, { r: 0, c: 0 }, 1)
+    const grid = mountCustomGame(setting, undefined, { seed })
 
-    // First safe cell: adjacent to the mine, shows "1", no cascade -> not yet won.
+    // First safe cell (col 0): adjacent to the mine, shows "1", no cascade -> not yet won.
     leftClick(grid.rows[0].cells[0])
     expect(grid.getAttribute('game-status')).toBe('active')
 
-    // Revealing the remaining safe cell completes the board.
+    // Revealing the remaining safe cell (col 2) completes the board.
     leftClick(grid.rows[0].cells[2])
     expect(grid.getAttribute('game-status')).toBe('done')
   })
 
   it('flood fill stops at a flagged cell and never reveals it', () => {
-    // 1x4 board with the mine pinned to the last column.
+    // 1x4 board; pin the mine to the last column so cols 0-2 are a safe run.
-    vi.spyOn(Math, 'random').mockReturnValue(0.99)
+    const setting = { rows: 1, cols: 4, mines: 1, id: 'test', name: 'test' }
-    const grid = mountCustomGame({ rows: 1, cols: 4, mines: 1, id: 'test', name: 'test' })
+    const seed = findSeedForMine(setting, { r: 0, c: 0 }, 3)
+    const grid = mountCustomGame(setting, undefined, { seed })
 
-    // Flag a safe cell sitting between the blank region and the mine.
+    // Flag a safe cell (col 2) sitting between the blank region and the mine.
     // (full press + release so the internal right-button flag resets)
     const flag = grid.rows[0].cells[2]
     flag.dispatchEvent(new MouseEvent('mousedown', { button: 2, bubbles: true }))

packages/mnswpr/test/replay-progress.test.js

@@ -0,0 +1,123 @@
+import { describe, it, expect } from 'vitest'
+import { GameSession, MinesweeperRules, generateBoard, levels } from '../core/index.js'
+import { createProgressReducer } from '../adapters/replay-progress.js'
+
+// Drive a session over an injected layout, capturing the real core-06 move-event
+// stream (onMove). Returns the emitted events and the session.
+function record(layout, moves) {
+  const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(layout) })
+  const events = []
+  session.onMove(e => events.push(e))
+  for (const m of moves) session.applyMove(m)
+  return { events: events.map(event => ({ seq: event.seq, t: event.t, event })), session }
+}
+
+// 3x3, single mine at (0,0); adjacency computed. Total safe = 8.
+const smallBoard = () => ({
+  rows: 3,
+  cols: 3,
+  mines: 1,
+  cells: [
+    [{ mine: true, adjacent: 0 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 1 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }]
+  ],
+  mineLocations: [[0, 0]]
+})
+
+describe('mnswpr progress reducer (percent-cleared)', () => {
+  it('progresses a scripted full game from 0% to 100%, monotonically', () => {
+    // A real generated board; reveal every safe cell in row-major order to win.
+    const layout = generateBoard(9, 9, 10, { seed: 7, safeCell: { r: 0, c: 0 } })
+    const progress = createProgressReducer(layout)
+
+    const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(layout) })
+    const events = []
+    session.onMove(e => events.push({ seq: e.seq, t: e.t, event: e }))
+    for (let r = 0; r < 9; r++) {
+      for (let c = 0; c < 9; c++) {
+        if (!session.state.grid.at(r, c).mine) session.applyMove({ type: 'reveal', r, c })
+      }
+    }
+    expect(session.status()).toBe('won')
+
+    expect(progress([])).toBe(0)                       // nothing revealed yet
+    expect(progress(events)).toBe(100)                 // full clear
+    expect(progress(events.slice(0, 1))).toBeGreaterThan(0) // first reveal opens a region
+
+    // monotonic non-decreasing across every prefix
+    let prev = -1
+    for (let k = 0; k <= events.length; k++) {
+      const p = progress(events.slice(0, k))
+      expect(p).toBeGreaterThanOrEqual(prev)
+      prev = p
+    }
+  })
+
+  it('counts flooded reveals by cells opened, not by event count', () => {
+    const layout = smallBoard()
+    const progress = createProgressReducer(layout)
+    // Revealing the far corner (2,2) floods every one of the 8 safe cells.
+    const { events } = record(layout, [{ type: 'reveal', r: 2, c: 2 }])
+    expect(events).toHaveLength(1)      // one event...
+    expect(progress(events)).toBe(100)  // ...but all 8 safe cells cleared
+  })
+
+  it('flag and unflag events leave progress unchanged', () => {
+    const layout = smallBoard()
+    const progress = createProgressReducer(layout)
+    // reveal one numbered cell (1/8), then flag + unflag the mine.
+    const { events } = record(layout, [
+      { type: 'reveal', r: 0, c: 1 }, // reveals just itself (adjacent 1)
+      { type: 'flag', r: 0, c: 0 },   // flag the mine
+      { type: 'flag', r: 0, c: 0 }    // unflag it
+    ])
+    expect(events.map(e => e.event.type)).toEqual(['reveal', 'flag', 'unflag'])
+
+    const afterReveal = progress(events.slice(0, 1))
+    expect(afterReveal).toBeCloseTo(12.5, 5) // 1 / 8
+    expect(progress(events.slice(0, 2))).toBe(afterReveal) // + flag: unchanged
+    expect(progress(events)).toBe(afterReveal)             // + unflag: unchanged
+  })
+
+  it('counts the cells a chord reveals', () => {
+    const layout = smallBoard()
+    const progress = createProgressReducer(layout)
+    // reveal (0,1)=1, flag the mine (0,0), then chord (0,1): its 1 flag matches
+    // its value, so it reveals the rest of the board.
+    const { events } = record(layout, [
+      { type: 'reveal', r: 0, c: 1 },
+      { type: 'flag', r: 0, c: 0 },
+      { type: 'chord', r: 0, c: 1 }
+    ])
+    expect(events.map(e => e.event.type)).toEqual(['reveal', 'flag', 'chord'])
+
+    expect(progress(events.slice(0, 1))).toBeCloseTo(12.5, 5) // 1/8 after reveal
+    expect(progress(events.slice(0, 2))).toBeCloseTo(12.5, 5) // flag doesn't advance
+    expect(progress(events)).toBe(100)                        // chord clears the rest
+  })
+
+  it('reflects a partial game (lost run stops where it stopped)', () => {
+    // Reveal a couple of cells then step on the mine — progress reflects only the
+    // safe cells cleared before the loss.
+    const layout = smallBoard()
+    const progress = createProgressReducer(layout)
+    const { events, session } = record(layout, [
+      { type: 'reveal', r: 0, c: 1 },
+      { type: 'reveal', r: 1, c: 0 },
+      { type: 'reveal', r: 0, c: 0 } // mine → lost
+    ])
+    expect(session.status()).toBe('lost')
+    expect(progress(events)).toBeCloseTo(25, 5) // 2 of 8 safe cells cleared
+  })
+
+  it('is usable as the replay engine progress adapter (shape check)', () => {
+    // The reducer matches ProgressReducer<T>: (events) => number in [0,100].
+    const { rows, cols, mines } = levels.beginner
+    const progress = createProgressReducer(generateBoard(rows, cols, mines, { seed: 1 }))
+    const v = progress([])
+    expect(typeof v).toBe('number')
+    expect(v).toBeGreaterThanOrEqual(0)
+    expect(v).toBeLessThanOrEqual(100)
+  })
+})

packages/mnswpr/test/replay-state.test.js

@@ -0,0 +1,104 @@
+import { describe, it, expect } from 'vitest'
+import { GameSession, MinesweeperRules } from '../core/index.js'
+import { createStateReducer } from '../adapters/replay-state.js'
+
+// Drive a session over an injected layout, capturing the real move-event stream.
+function record(layout, moves) {
+  const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(layout) })
+  const events = []
+  session.onMove(e => events.push(e))
+  for (const m of moves) session.applyMove(m)
+  return { events: events.map(event => ({ seq: event.seq, t: event.t, event })), session }
+}
+
+// 3x3, single mine at (0,0). Total safe = 8.
+const smallBoard = () => ({
+  rows: 3,
+  cols: 3,
+  mines: 1,
+  cells: [
+    [{ mine: true, adjacent: 0 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 1 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }]
+  ],
+  mineLocations: [[0, 0]]
+})
+
+describe('mnswpr state reducer (full-board reconstruction)', () => {
+  const layout = smallBoard()
+  const { events } = record(layout, [
+    { type: 'reveal', r: 0, c: 1 },
+    { type: 'reveal', r: 1, c: 0 },
+    { type: 'flag', r: 0, c: 0 },
+    { type: 'reveal', r: 2, c: 2 } // floods the rest
+  ])
+  const state = createStateReducer(layout)
+  const status = (b, r, c) => b.cells[r][c].status
+
+  it('empty slice → pristine board (all hidden, fresh)', () => {
+    const b = state([])
+    expect(b.rows).toBe(3)
+    expect(b.cols).toBe(3)
+    expect(b.phase).toBe('fresh')
+    expect(b.revealedSafe).toBe(0)
+    expect(b.cells.flat().every(c => c.status === 'hidden')).toBe(true)
+  })
+
+  it('reconstructs the exact board state at several event indices', () => {
+    // index 1 — after reveal(0,1): just that cell open
+    let b = state(events.slice(0, 1))
+    expect(status(b, 0, 1)).toBe('revealed')
+    expect(status(b, 0, 0)).toBe('hidden')
+    expect(status(b, 1, 0)).toBe('hidden')
+    expect(b.revealedSafe).toBe(1)
+    expect(b.phase).toBe('active')
+
+    // index 2 — after reveal(1,0)
+    b = state(events.slice(0, 2))
+    expect(status(b, 0, 1)).toBe('revealed')
+    expect(status(b, 1, 0)).toBe('revealed')
+    expect(b.revealedSafe).toBe(2)
+
+    // index 3 — after flag(0,0): mine flagged, nothing new revealed
+    b = state(events.slice(0, 3))
+    expect(status(b, 0, 0)).toBe('flagged')
+    expect(b.revealedSafe).toBe(2)
+
+    // index 4 — after reveal(2,2): floods all safe cells; mine stays flagged; won
+    b = state(events.slice(0, 4))
+    expect(b.phase).toBe('won')
+    expect(b.revealedSafe).toBe(8)
+    for (let r = 0; r < 3; r++) {
+      for (let c = 0; c < 3; c++) {
+        expect(status(b, r, c)).toBe(r === 0 && c === 0 ? 'flagged' : 'revealed')
+      }
+    }
+  })
+
+  it('carries mine/adjacent metadata for rendering', () => {
+    const b = state(events)
+    expect(b.cells[0][0].mine).toBe(true)
+    expect(b.cells[0][1].mine).toBe(false)
+    expect(b.cells[0][1].adjacent).toBe(1)
+  })
+
+  it('is stateless: the same slice reconstructs an equal board', () => {
+    expect(state(events.slice(0, 2))).toEqual(state(events.slice(0, 2)))
+    // and reconstructing a shorter slice after a longer one is unaffected
+    const full = state(events)
+    expect(state(events.slice(0, 1)).revealedSafe).toBe(1)
+    expect(full.revealedSafe).toBe(8)
+  })
+
+  it('counts chord reveals in the reconstructed board', () => {
+    // reveal a number, flag the mine, then chord it open.
+    const { events: chordEvents } = record(smallBoard(), [
+      { type: 'reveal', r: 0, c: 1 },
+      { type: 'flag', r: 0, c: 0 },
+      { type: 'chord', r: 0, c: 1 }
+    ])
+    const b = createStateReducer(smallBoard())(chordEvents)
+    expect(b.revealedSafe).toBe(8)
+    expect(b.cells[2][2].status).toBe('revealed')
+  })
+})

packages/move-log/README.md

@@ -0,0 +1,62 @@
+# @cozy-games/move-log
+
+A **game-agnostic** container for a recorded run of move events. It wraps any game's event stream in a schema-versioned, ordered, timestamped log.
+
+```js
+import {
+  createMoveLog, withReceivedTs,
+  serializeMoveLog, deserializeMoveLog, isMoveLog, SCHEMA_VERSION
+} from '@cozy-games/move-log'
+
+// `T` is your game's own event vocabulary — supplied by you, unknown to us.
+const log = createMoveLog([
+  { seq: 1, t: 0, event: { type: 'reveal', r: 0, c: 0 } },
+  { seq: 2, t: 50, event: { type: 'flag', r: 1, c: 2 } }
+])
+// → { schema_version: 1, events: [ { seq, t, event }, ... ] }
+
+const json = serializeMoveLog(log)          // → JSON string
+const restored = deserializeMoveLog(json)    // → validated MoveLog, or throws
+
+// A consumer records WHEN it received events (host clock), additively:
+const stamped = withReceivedTs(restored, () => hostNow())
+// → each event now also carries `receivedTs`; still a valid v1 log
+```
+
+## Shape
+
+| field            | type              | meaning                                            |
+| ---------------- | ----------------- | -------------------------------------------------- |
+| `schema_version` | `1`               | the move-log container version                     |
+| `events`         | `MoveEvent<T>[]`  | ordered, each `{ seq, t, event, receivedTs? }`     |
+
+`MoveEvent<T> = { seq: number, t: number, event: T, receivedTs?: number }` — the
+log owns the per-event recording metadata (a strictly increasing `seq`, a
+source-side timestamp `t`, and an **optional** received-side `receivedTs`), so
+`T` stays a pure game payload with no required shape. `receivedTs` is
+purpose-neutral: it records only *that* a consumer received the event at some
+time, never why or from where.
+
+`deserializeMoveLog` round-trips a serialized log with full fidelity (order,
+timestamps, sequence numbers, and any `receivedTs`) and rejects malformed input —
+bad JSON, missing or wrong-typed fields, or non-monotonic `seq` — with a clear
+error, never returning a partially-parsed log.
+
+## Versioning: `receivedTs` is additive within `schema_version: 1`
+
+`receivedTs` was added **without** bumping `schema_version`. It is optional and
+purely additive: a v1 log is valid whether every event, some events, or no
+events carry a `receivedTs`, and a reader that doesn't know the field simply
+ignores it. A version bump is reserved for *breaking* container changes (a
+renamed/removed field or a newly required one), which would be dispatched on in
+`deserializeMoveLog`. See the `SCHEMA_VERSION` doc comment for the full policy.
+
+## Invariant: zero game-specific imports
+
+This module **must never import a game package** (e.g. mnswpr) or any game
+vocabulary. `T` is always supplied by the consumer; the log only ever sees
+opaque payloads. This independence is the whole point — it lets one move-log
+format serve every game.
+
+The rule is enforced by a dependency-graph guard in `test/move-log.test.js`
+(scans the package's source and manifest for game references). Keep it green.

packages/move-log/index.js

@@ -0,0 +1,219 @@
+// @ts-check
+
+/**
+ * `@cozy-games/move-log` — a game-agnostic container for a recorded run of move
+ * events. It wraps ANY game's event stream: `T` is the consuming game's own
+ * event vocabulary (mnswpr's `MoveEvent` union from core-06 is the first `T`),
+ * supplied by the caller.
+ *
+ * This module imports NO game types — that independence is the whole point and
+ * is enforced by a dependency-graph guard in the tests. The log owns the
+ * per-event recording metadata (`seq` + `t`, and an optional received-side
+ * `receivedTs`) so `T` can stay a pure game payload with no required shape; the
+ * module never inspects the inside of an `event`.
+ *
+ * Extraction to a standalone published package comes later; for now it lives as
+ * a shared workspace module alongside `packages/utils`.
+ */
+
+/**
+ * The move-log schema version.
+ *
+ * Versioning policy: OPTIONAL, purely additive fields (an event gaining an
+ * optional `receivedTs`, say) do NOT bump this — a v1 reader ignores fields it
+ * doesn't know, and a log written with them stays a valid v1 log. Bump ONLY on a
+ * breaking change to the container shape (a renamed/removed field, a newly
+ * *required* field), which would need dispatch on read. Never bump for changes
+ * to a game's `T` vocabulary.
+ *
+ * @typedef {1} SchemaVersion
+ */
+export const SCHEMA_VERSION = /** @type {SchemaVersion} */ (1)
+
+/**
+ * A single recorded event: the log-owned recording metadata — a strictly
+ * increasing sequence number `seq`, a source-side timestamp `t` (milliseconds),
+ * and an OPTIONAL received-side timestamp `receivedTs` a consumer may attach when
+ * it received the event — plus the game's opaque payload `event`. Generic over
+ * the game's event type `T`. `receivedTs` is purpose-neutral: the log records
+ * only THAT it was received at some time, never why or from where.
+ *
+ * @template T
+ * @typedef {{ seq: number, t: number, event: T, receivedTs?: number }} MoveEvent
+ */
+
+/**
+ * The container: a schema-versioned, ordered array of timestamped, sequenced
+ * events for one recorded run. Generic over the game's event vocabulary `T`.
+ * JSON-safe as long as `T` is.
+ *
+ * @template T
+ * @typedef {{ schema_version: SchemaVersion, events: MoveEvent<T>[] }} MoveLog
+ */
+
+/**
+ * Validate an events array: each entry must be a `{ seq, t, event }` with an
+ * integer `seq`, a finite numeric `t`, and a present `event`; and `seq` must be
+ * STRICTLY INCREASING across the array. Throws a distinct, field-specific error
+ * on the first problem — never leaves a caller with a half-checked array.
+ *
+ * @param {unknown} events
+ */
+function assertEvents(events) {
+  if (!Array.isArray(events)) {
+    throw new TypeError(`move-log: events must be an array (got ${events === null ? 'null' : typeof events})`)
+  }
+  let prevSeq = -Infinity
+  events.forEach((e, i) => {
+    if (e === null || typeof e !== 'object') {
+      throw new TypeError(`move-log: events[${i}] must be an object (got ${e === null ? 'null' : typeof e})`)
+    }
+    if (!('event' in e)) {
+      throw new TypeError(`move-log: events[${i}] is missing 'event'`)
+    }
+    if (typeof e.t !== 'number' || !Number.isFinite(e.t)) {
+      throw new TypeError(`move-log: events[${i}].t must be a finite number (got ${JSON.stringify(e.t)})`)
+    }
+    if (!Number.isInteger(e.seq)) {
+      throw new TypeError(`move-log: events[${i}].seq must be an integer (got ${JSON.stringify(e.seq)})`)
+    }
+    if (e.seq <= prevSeq) {
+      throw new RangeError(`move-log: events[${i}].seq must be strictly increasing (got ${e.seq} after ${prevSeq})`)
+    }
+    if (e.receivedTs !== undefined && (typeof e.receivedTs !== 'number' || !Number.isFinite(e.receivedTs))) {
+      throw new TypeError(`move-log: events[${i}].receivedTs must be a finite number when present (got ${JSON.stringify(e.receivedTs)})`)
+    }
+    prevSeq = e.seq
+  })
+}
+
+/**
+ * Copy one event record to the canonical field set, carrying `receivedTs`
+ * through only when it's actually present (so absent stays absent — no
+ * `receivedTs: undefined` keys leak into the log or its JSON).
+ *
+ * @template T
+ * @param {MoveEvent<T>} e
+ * @returns {MoveEvent<T>}
+ */
+function copyEvent(e) {
+  /** @type {MoveEvent<T>} */
+  const out = { seq: e.seq, t: e.t, event: e.event }
+  if (e.receivedTs !== undefined) out.receivedTs = e.receivedTs
+  return out
+}
+
+/**
+ * Assert a value is a well-formed move log — correct `schema_version` and a valid
+ * events array — throwing a clear, specific error otherwise. Returns the value
+ * (typed) for chaining; never mutates.
+ *
+ * @param {unknown} value
+ * @returns {MoveLog<any>}
+ */
+export function assertMoveLog(value) {
+  if (value === null || typeof value !== 'object') {
+    throw new TypeError(`move-log: expected an object (got ${value === null ? 'null' : typeof value})`)
+  }
+  const v = /** @type {any} */ (value)
+  if (v.schema_version !== SCHEMA_VERSION) {
+    throw new RangeError(`move-log: unsupported schema_version ${JSON.stringify(v.schema_version)} (expected ${SCHEMA_VERSION})`)
+  }
+  assertEvents(v.events)
+  return v
+}
+
+/**
+ * Build a move log from an ordered list of `{ seq, t, event }` records. Pure and
+ * game-agnostic: it validates only the log's own invariants (metadata types and
+ * strictly increasing `seq`), never the shape of `T`. Order is preserved and
+ * entries are copied, so the log never aliases the caller's array.
+ *
+ * @template T
+ * @param {MoveEvent<T>[]} [events] - ordered events, each `{ seq, t, event, receivedTs? }`
+ * @returns {MoveLog<T>}
+ */
+export function createMoveLog(events = []) {
+  assertEvents(events)
+  return {
+    schema_version: SCHEMA_VERSION,
+    events: events.map(copyEvent)
+  }
+}
+
+/**
+ * Return a new move log with a received-side timestamp attached to each event
+ * for which `stamp` returns a finite number; events where `stamp` returns
+ * `undefined` are left as-is (keeping any existing `receivedTs`). This is how a
+ * consumer records WHEN it received events — the log never cares where the value
+ * came from. Pure: the input log is not mutated.
+ *
+ * @template T
+ * @param {MoveLog<T>} log
+ * @param {(event: MoveEvent<T>, index: number) => number | undefined} stamp
+ * @returns {MoveLog<T>}
+ */
+export function withReceivedTs(log, stamp) {
+  assertMoveLog(log)
+  const events = log.events.map((e, i) => {
+    const rt = stamp(e, i)
+    if (rt === undefined) return copyEvent(e)
+    if (typeof rt !== 'number' || !Number.isFinite(rt)) {
+      throw new TypeError(`withReceivedTs: stamp must return a finite number or undefined (got ${JSON.stringify(rt)} at index ${i})`)
+    }
+    return { ...copyEvent(e), receivedTs: rt }
+  })
+  return { schema_version: log.schema_version, events }
+}
+
+/**
+ * Non-throwing type guard: is `value` a well-formed move log of the current
+ * schema version? Checks the container invariants only — remains blind to `T`.
+ *
+ * @param {unknown} value
+ * @returns {boolean}
+ */
+export function isMoveLog(value) {
+  try {
+    assertMoveLog(value)
+    return true
+  } catch {
+    return false
+  }
+}
+
+/**
+ * Serialize a move log to a JSON string. Validates first, so a malformed log is
+ * rejected here rather than emitted. Inverse of {@link deserializeMoveLog}.
+ *
+ * @template T
+ * @param {MoveLog<T>} log
+ * @returns {string}
+ */
+export function serializeMoveLog(log) {
+  assertMoveLog(log)
+  return JSON.stringify(log)
+}
+
+/**
+ * Parse and validate a JSON string into a move log, with full fidelity: event
+ * order, timestamps, and sequence numbers survive the round-trip exactly.
+ * Rejects malformed input (bad JSON, missing/typed-wrong fields, non-monotonic
+ * `seq`) with a clear error and NEVER returns a partially-parsed log. Inverse of
+ * {@link serializeMoveLog}.
+ *
+ * @param {string} json
+ * @returns {MoveLog<any>}
+ */
+export function deserializeMoveLog(json) {
+  if (typeof json !== 'string') {
+    throw new TypeError(`deserializeMoveLog: expected a JSON string (got ${json === null ? 'null' : typeof json})`)
+  }
+  let parsed
+  try {
+    parsed = JSON.parse(json)
+  } catch (err) {
+    throw new SyntaxError(`deserializeMoveLog: invalid JSON — ${/** @type {Error} */ (err).message}`, { cause: err })
+  }
+  return assertMoveLog(parsed)
+}

packages/move-log/package.json

@@ -0,0 +1,22 @@
+{
+  "name": "@cozy-games/move-log",
+  "version": "0.0.1",
+  "description": "Game-blind, schema-versioned log of a recorded run of move events — generic over the game's own event vocabulary",
+  "author": "Ayo Ayco",
+  "private": true,
+  "type": "module",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/ayo-run/mnswpr"
+  },
+  "main": "index.js",
+  "exports": {
+    ".": {
+      "default": "./index.js"
+    },
+    "./*": {
+      "default": "./*"
+    }
+  },
+  "license": "BSD-2-Clause"
+}

packages/move-log/test/move-log.test.js

@@ -0,0 +1,323 @@
+// @ts-check
+import { describe, it, expect } from 'vitest'
+import { readFileSync, readdirSync, statSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { dirname, join } from 'node:path'
+
+// Imported via the PACKAGE NAME (not a relative path) to prove the workspace
+// module resolves and is importable by other packages.
+import {
+  createMoveLog, withReceivedTs,
+  serializeMoveLog, deserializeMoveLog, isMoveLog, assertMoveLog, SCHEMA_VERSION
+} from '@cozy-games/move-log'
+
+// A REAL mnswpr session/event stream — imported by the TEST, never the module.
+// Relative path (not the package name) so no game dependency enters the manifest.
+import { GameSession, MinesweeperRules } from '../../mnswpr/core/index.js'
+
+/**
+ * A dummy event vocabulary defined HERE, in the test — deliberately NOT mnswpr's.
+ * The move log must type-check and work against any `T` the consumer supplies.
+ * @typedef {{ kind: 'tick' } | { kind: 'boom', power: number }} DummyEvent
+ */
+
+describe('@cozy-games/move-log', () => {
+  /** @type {import('@cozy-games/move-log').MoveEvent<DummyEvent>[]} */
+  const events = [
+    { seq: 1, t: 0, event: { kind: 'tick' } },
+    { seq: 2, t: 50, event: { kind: 'boom', power: 3 } },
+    { seq: 5, t: 120, event: { kind: 'tick' } } // gaps allowed; strictly increasing
+  ]
+
+  it('exposes schema_version typed as 1', () => {
+    expect(SCHEMA_VERSION).toBe(1)
+  })
+
+  it('wraps an ordered, timestamped, sequenced stream for a dummy vocabulary', () => {
+    /** @type {import('@cozy-games/move-log').MoveLog<DummyEvent>} */
+    const log = createMoveLog(events)
+
+    expect(log.schema_version).toBe(1)
+    expect(log.events).toHaveLength(3)
+    expect(log.events.map(e => e.seq)).toEqual([1, 2, 5])
+    expect(log.events.map(e => e.t)).toEqual([0, 50, 120])
+    expect(log.events[1]).toEqual({ seq: 2, t: 50, event: { kind: 'boom', power: 3 } })
+  })
+
+  it('defaults to an empty run and copies entries (no aliasing of the input)', () => {
+    expect(createMoveLog()).toEqual({ schema_version: 1, events: [] })
+    const input = [{ seq: 1, t: 1, event: { kind: 'tick' } }]
+    const log = createMoveLog(input)
+    input[0].t = 999
+    expect(log.events[0].t).toBe(1) // log kept its own copy
+  })
+
+  it('rejects a non-monotonic seq at construction', () => {
+    expect(() => createMoveLog([
+      { seq: 2, t: 0, event: {} },
+      { seq: 1, t: 1, event: {} }
+    ])).toThrow(RangeError)
+  })
+})
+
+describe('serialization round-trip', () => {
+  const events = [
+    { seq: 1, t: 0, event: { type: 'reveal', r: 0, c: 0 } },
+    { seq: 2, t: 50, event: { type: 'flag', r: 1, c: 2 } },
+    { seq: 3, t: 90, event: { type: 'chord', r: 4, c: 4 } }
+  ]
+
+  it('preserves order, timestamps, and sequence numbers exactly', () => {
+    const log = createMoveLog(events)
+    const restored = deserializeMoveLog(serializeMoveLog(log))
+
+    expect(restored).toEqual(log) // full structural fidelity
+    expect(restored.events.map(e => e.seq)).toEqual([1, 2, 3])
+    expect(restored.events.map(e => e.t)).toEqual([0, 50, 90])
+    expect(restored.events.map(e => e.event.type)).toEqual(['reveal', 'flag', 'chord'])
+  })
+
+  it('serializeMoveLog produces a JSON string parseable back to the same object', () => {
+    const log = createMoveLog(events)
+    const json = serializeMoveLog(log)
+    expect(typeof json).toBe('string')
+    expect(JSON.parse(json)).toEqual(log)
+  })
+
+  it('rejects each malformed fixture with a distinct, clear error', () => {
+    const valid = serializeMoveLog(createMoveLog(events))
+
+    // not a string
+    // @ts-expect-error — deliberately wrong type
+    expect(() => deserializeMoveLog({})).toThrow(TypeError)
+    // invalid JSON syntax
+    expect(() => deserializeMoveLog('{not json')).toThrow(SyntaxError)
+    // missing schema_version
+    expect(() => deserializeMoveLog(JSON.stringify({ events: [] }))).toThrow(RangeError)
+    // wrong schema_version
+    expect(() => deserializeMoveLog(JSON.stringify({ schema_version: 2, events: [] }))).toThrow(RangeError)
+    // events not an array
+    expect(() => deserializeMoveLog(JSON.stringify({ schema_version: 1, events: 'nope' }))).toThrow(TypeError)
+    // missing 'event' field
+    expect(() => deserializeMoveLog(JSON.stringify({ schema_version: 1, events: [{ seq: 1, t: 0 }] }))).toThrow(TypeError)
+    // bad timestamp type
+    expect(() => deserializeMoveLog(JSON.stringify({ schema_version: 1, events: [{ seq: 1, t: 'soon', event: {} }] }))).toThrow(TypeError)
+    // bad seq type
+    expect(() => deserializeMoveLog(JSON.stringify({ schema_version: 1, events: [{ seq: 1.5, t: 0, event: {} }] }))).toThrow(TypeError)
+    // shuffled / non-monotonic seq
+    const shuffled = JSON.stringify({
+      schema_version: 1,
+      events: [{ seq: 3, t: 0, event: {} }, { seq: 1, t: 1, event: {} }]
+    })
+    expect(() => deserializeMoveLog(shuffled)).toThrow(RangeError)
+
+    // distinct messages, not one generic error
+    const messages = [
+      captureMessage(() => deserializeMoveLog('{not json')),
+      captureMessage(() => deserializeMoveLog(JSON.stringify({ events: [] }))),
+      captureMessage(() => deserializeMoveLog(JSON.stringify({ schema_version: 1, events: [{ seq: 1, t: 0 }] }))),
+      captureMessage(() => deserializeMoveLog(shuffled))
+    ]
+    expect(new Set(messages).size).toBe(messages.length)
+
+    // sanity: the valid fixture still deserializes
+    expect(isMoveLog(deserializeMoveLog(valid))).toBe(true)
+  })
+
+  it('never returns a partially-parsed log (throws before returning)', () => {
+    const partlyBad = JSON.stringify({
+      schema_version: 1,
+      events: [{ seq: 1, t: 0, event: { ok: true } }, { seq: 2, t: 'bad', event: {} }]
+    })
+    let result = 'sentinel'
+    expect(() => { result = deserializeMoveLog(partlyBad) }).toThrow(TypeError)
+    expect(result).toBe('sentinel') // assignment never happened
+  })
+
+  it('isMoveLog / assertMoveLog agree on validity', () => {
+    const log = createMoveLog(events)
+    expect(isMoveLog(log)).toBe(true)
+    expect(assertMoveLog(log)).toBe(log)
+    expect(isMoveLog(null)).toBe(false)
+    expect(isMoveLog({ schema_version: 1, events: [{ seq: 1, t: 0 }] })).toBe(false)
+  })
+})
+
+describe('received timestamps (additive receivedTs)', () => {
+  const base = [
+    { seq: 1, t: 0, event: { type: 'reveal', r: 0, c: 0 } },
+    { seq: 2, t: 50, event: { type: 'flag', r: 1, c: 2 } }
+  ]
+
+  it('accepts an optional receivedTs per event and round-trips it', () => {
+    const log = createMoveLog([
+      { seq: 1, t: 0, event: { k: 'a' }, receivedTs: 1000 },
+      { seq: 2, t: 50, event: { k: 'b' }, receivedTs: 1060 }
+    ])
+    expect(log.events[0].receivedTs).toBe(1000)
+    const restored = deserializeMoveLog(serializeMoveLog(log))
+    expect(restored).toEqual(log)
+    expect(restored.events.map(e => e.receivedTs)).toEqual([1000, 1060])
+  })
+
+  it('is valid with receivedTs on only some events', () => {
+    const log = createMoveLog([
+      { seq: 1, t: 0, event: { k: 'a' }, receivedTs: 1000 },
+      { seq: 2, t: 50, event: { k: 'b' } } // no receivedTs
+    ])
+    expect(isMoveLog(log)).toBe(true)
+    expect('receivedTs' in log.events[1]).toBe(false)
+    expect(deserializeMoveLog(serializeMoveLog(log))).toEqual(log)
+  })
+
+  it('REGRESSION: a log with no receivedTs anywhere stays fully valid and leaks no key', () => {
+    const log = createMoveLog(base)
+    expect(isMoveLog(log)).toBe(true)
+    expect(log.events.every(e => !('receivedTs' in e))).toBe(true)
+    const restored = deserializeMoveLog(serializeMoveLog(log))
+    expect(restored).toEqual(log)
+    expect(restored.events.every(e => !('receivedTs' in e))).toBe(true)
+  })
+
+  it('rejects a non-finite / non-numeric receivedTs', () => {
+    expect(() => createMoveLog([{ seq: 1, t: 0, event: {}, receivedTs: 'soon' }])).toThrow(TypeError)
+    expect(() => createMoveLog([{ seq: 1, t: 0, event: {}, receivedTs: Infinity }])).toThrow(TypeError)
+    expect(() => deserializeMoveLog(JSON.stringify({
+      schema_version: 1,
+      events: [{ seq: 1, t: 0, event: {}, receivedTs: 'later' }]
+    }))).toThrow(TypeError)
+  })
+
+  it('withReceivedTs attaches host-received times additively without mutating the input', () => {
+    const log = createMoveLog(base)
+    let clock = 900
+    const stamped = withReceivedTs(log, () => (clock += 10))
+
+    // input untouched
+    expect(log.events.every(e => !('receivedTs' in e))).toBe(true)
+    // output stamped, still a valid v1 log, round-trips
+    expect(stamped.events.map(e => e.receivedTs)).toEqual([910, 920])
+    expect(stamped.schema_version).toBe(1)
+    expect(deserializeMoveLog(serializeMoveLog(stamped))).toEqual(stamped)
+  })
+
+  it('withReceivedTs leaves events unstamped when the stamp returns undefined', () => {
+    const log = createMoveLog(base)
+    const stamped = withReceivedTs(log, (e) => (e.seq === 1 ? 1234 : undefined))
+    expect(stamped.events[0].receivedTs).toBe(1234)
+    expect('receivedTs' in stamped.events[1]).toBe(false)
+    expect(isMoveLog(stamped)).toBe(true)
+  })
+
+  it('withReceivedTs rejects a stamp that returns a non-finite number', () => {
+    const log = createMoveLog(base)
+    expect(() => withReceivedTs(log, () => NaN)).toThrow(TypeError)
+  })
+
+  it('VERSIONING: receivedTs is additive — same schema_version with or without it', () => {
+    const without = createMoveLog(base)
+    const withRt = withReceivedTs(without, () => 1000)
+    expect(without.schema_version).toBe(SCHEMA_VERSION)
+    expect(withRt.schema_version).toBe(SCHEMA_VERSION)
+    expect(SCHEMA_VERSION).toBe(1)
+    // a v1 reader accepts both shapes
+    expect(isMoveLog(without)).toBe(true)
+    expect(isMoveLog(withRt)).toBe(true)
+  })
+})
+
+describe('integration: wraps a real mnswpr event stream (core-06)', () => {
+  // 3x3, single mine at (0,0); adjacency computed. Lets us script exact moves.
+  const layout = {
+    rows: 3,
+    cols: 3,
+    mines: 1,
+    cells: [
+      [{ mine: true, adjacent: 0 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+      [{ mine: false, adjacent: 1 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+      [{ mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }]
+    ],
+    mineLocations: [[0, 0]]
+  }
+
+  it('records an mnswpr session end-to-end and round-trips it losslessly', () => {
+    let now = 1000
+    const clock = () => now
+    const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(layout), clock })
+
+    // Capture the real core-06 move-events ({ type, r, c, t, seq }).
+    /** @type {any[]} */
+    const emitted = []
+    session.onMove(e => emitted.push(e))
+
+    now = 1050; session.applyMove({ type: 'reveal', r: 0, c: 1 })
+    now = 1100; session.applyMove({ type: 'flag', r: 0, c: 0 })
+    now = 1150; session.applyMove({ type: 'flag', r: 0, c: 0 }) // unflag
+    now = 1200; session.applyMove({ type: 'flag', r: 0, c: 0 }) // re-flag the mine
+    now = 1250; session.applyMove({ type: 'chord', r: 0, c: 1 }) // 1 flag == value → chord
+
+    expect(emitted.map(e => e.type)).toEqual(['reveal', 'flag', 'unflag', 'flag', 'chord'])
+
+    // Wrap the stream: lift the recording metadata (seq, t) to the log level.
+    const log = createMoveLog(emitted.map(e => ({ seq: e.seq, t: e.t, event: e })))
+    const restored = deserializeMoveLog(serializeMoveLog(log))
+
+    expect(restored).toEqual(log)
+    expect(restored.events.map(e => e.seq)).toEqual([1, 2, 3, 4, 5])
+    expect(restored.events.map(e => e.t)).toEqual([1050, 1100, 1150, 1200, 1250])
+    expect(restored.events.map(e => e.event.type)).toEqual(['reveal', 'flag', 'unflag', 'flag', 'chord'])
+    // sequence is strictly increasing — the log's own invariant, verified on real data
+    const seqs = restored.events.map(e => e.seq)
+    expect(seqs).toEqual([...seqs].sort((a, b) => a - b))
+  })
+})
+
+describe('game-agnosticism guard (zero game-specific imports)', () => {
+  const pkgDir = join(dirname(fileURLToPath(import.meta.url)), '..')
+
+  // The set of game packages the move log must never depend on or import.
+  const GAME_REFERENCES = /mnswpr|minesweeper/i
+
+  it('manifest declares no dependency on a game package', () => {
+    const pkg = JSON.parse(readFileSync(join(pkgDir, 'package.json'), 'utf8'))
+    const deps = {
+      ...pkg.dependencies,
+      ...pkg.devDependencies,
+      ...pkg.peerDependencies
+    }
+    const offenders = Object.keys(deps).filter(name => GAME_REFERENCES.test(name))
+    expect(offenders).toEqual([])
+  })
+
+  it('no source file imports or references a game package', () => {
+    const offenders = []
+    walk(pkgDir, file => {
+      if (!file.endsWith('.js')) return
+      if (file.includes('/test/')) return // the test may name/import games on purpose
+      // Strip comments so prose that *names* a game isn't a false positive.
+      const code = readFileSync(file, 'utf8')
+        .replace(/\/\*[\s\S]*?\*\//g, '')
+        .replace(/\/\/.*$/gm, '')
+      if (GAME_REFERENCES.test(code)) offenders.push(file)
+    })
+    expect(offenders).toEqual([])
+  })
+})
+
+function captureMessage(fn) {
+  try {
+    fn()
+    return null
+  } catch (err) {
+    return err.message
+  }
+}
+
+function walk(dir, fn) {
+  for (const name of readdirSync(dir)) {
+    if (name === 'node_modules') continue
+    const p = join(dir, name)
+    if (statSync(p).isDirectory()) walk(p, fn)
+    else fn(p)
+  }
+}

packages/replay/README.md

@@ -0,0 +1,150 @@
+# @cozy-games/replay
+
+A **game-agnostic** replay engine. `PlaybackClock` re-drives a
+[`@cozy-games/move-log`](../move-log) envelope over time — scheduling each
+recorded event to fire at its offset — with `play` / `pause` / `seek`.
+
+```js
+import { PlaybackClock } from '@cozy-games/replay'
+
+const clock = new PlaybackClock(envelope)     // a valid move-log envelope
+const off = clock.on(record => apply(record.event)) // record = { seq, t, event, ... }
+
+clock.play()      // events fire at their recorded offsets
+clock.pause()     // freeze at the current position
+clock.seek(1500)  // jump to 1500ms — delivers exactly the events at offset <= 1500
+```
+
+## Progress via a game adapter
+
+The engine never interprets events. To show completion percent, supply a game
+**adapter** with a `progress(events) → %` reducer at construction:
+
+```js
+const adapter = { progress: (events) => (events.length / total) * 100 }
+const clock = new PlaybackClock(envelope, {}, adapter)
+
+clock.seek(1500)
+clock.progress() // 0–100 (clamped), or null if no adapter supplied
+```
+
+The reducer receives the ordered slice of events delivered so far; the engine
+clamps the result and stays blind to the payload. See
+[docs/adapter-interface.md](./docs/adapter-interface.md) for the full contract.
+
+### Progress mode: a signal over time
+
+`onProgress` turns the clock + reducer into a live "percent complete over elapsed
+time" signal — updates as playback advances, on seek forward, and on seek back:
+
+```js
+const clock = new PlaybackClock(envelope, {}, adapter)
+clock.onProgress(({ position, progress }) => draw(position, progress))
+clock.play()
+```
+
+Fidelity is exact: at playback time `t` the delivered set is precisely the events
+at offset `≤ t`, so the emitted `progress` matches the original run's progress at
+`t`. Updates fire only when the percentage moves (a flag/unflag emits nothing).
+Subscribe before playing to catch every update; call `progress()` for the current
+value at any time.
+
+### Full-board mode (flag-gated)
+
+With a `state` reducer and the `fullBoard` flag, the engine reconstructs the whole
+board at any point — `state()` for the current board, `onState` for a stream, and
+`seek(t)` rebuilds the exact state at `t`:
+
+```js
+const clock = new PlaybackClock(envelope, {}, adapter, { fullBoard: true })
+clock.onState(({ position, state }) => render(state))
+clock.seek(1500) // state() now reflects the board at 1500ms
+```
+
+Off by default: without the flag, `state()` is `null`, `onState` never fires, and
+the reducer never runs. See [docs/adapter-interface.md](./docs/adapter-interface.md).
+
+### The "ended" signal & partial recordings
+
+`onEnd` fires with `{ position }` when playback reaches the **last recorded
+event's offset**:
+
+```js
+clock.onEnd(({ position }) => showEndScreen())
+```
+
+The engine has no notion of a "terminal" event, so this is the *same* signal
+whether the run completed or the recording was **truncated mid-game**. A partial
+log plays up to its last event and stops cleanly in both progress and full-board
+modes — no error for the mere absence of a terminal event. Progress **freezes at
+its last computed value** (no extrapolation, no jump to 100%), because it's purely
+the reducer over the delivered events. The signal re-arms if you seek back before
+the end.
+
+## Offsets
+
+Each event fires at its **offset** — its recorded `t` minus the first event's
+`t`, so playback time `0` is the first event. `duration` is the last event's
+offset.
+
+## Injected clock + scheduler
+
+The time source and scheduler are injected (mirroring the core session's
+injected-clock seam), so tests get exact, deterministic timing:
+
+```js
+new PlaybackClock(envelope, { clock, setTimeout, clearTimeout })
+```
+
+They default to the real host (`Date.now` + global timers). Under a deterministic
+injected scheduler — or `vi.useFakeTimers()` — events fire **exactly** at their
+offsets (tolerance 0). Under the real host scheduler the tolerance is the host's
+timer resolution (a few ms), the same bound as any `setTimeout`.
+
+## Seek is deterministic
+
+The clock keeps one invariant: `cursor` = the number of events whose offset is
+`<= position`. So after `seek(t)` the delivered set is exactly the events at
+offset `<= t`:
+
+- **Forward** (`seek` ahead, or playback advancing) delivers each newly-passed
+  event once, in order.
+- **Backward** rewinds the cursor without delivering; passing those offsets again
+  going forward re-delivers them (so scrub-back-then-replay works).
+
+No event is ever delivered twice for a single forward pass, and none is dropped.
+
+## Schema-version dispatch
+
+One engine build replays envelopes from multiple format generations. On
+construction the envelope is routed by its `schema_version` through a dispatch
+table to a version-specific **reader** that normalizes it into the canonical
+`MoveEvent` records the engine plays:
+
+```js
+readEnvelope(envelope)            // → canonical records, or throws
+```
+
+- **v1** is the only built-in reader today (the canonical format itself).
+- **Unknown versions fail loudly** — never a silent best-effort parse:
+
+  ```
+  readEnvelope: unsupported envelope schema_version 99 (supported: 1)
+  ```
+
+- **Adding a generation is one entry.** Register a reader for this instance via
+  the `readers` option (or add to the built-in table for a permanent version):
+
+  ```js
+  const v2 = (env) => env.log.map(e => ({ seq: e.n, t: e.ts, event: e.payload }))
+  new PlaybackClock(v2Envelope, {}, adapter, { readers: { 2: v2 } })
+  ```
+
+  Whatever a reader returns is validated as a canonical move log, so a
+  half-normalized generation can never reach the engine.
+
+## Invariant: envelope only, no game types
+
+This module imports **only** `@cozy-games/move-log` (to validate the envelope) and
+never a game package. It treats every `event` payload as opaque. Enforced by a
+dependency-graph guard in `test/playback-clock.test.js`.

packages/replay/docs/adapter-interface.md

@@ -0,0 +1,94 @@
+# Replay adapter interface
+
+The replay engine is **game-agnostic**: it schedules and delivers the events in a
+[`@cozy-games/move-log`](../../move-log) envelope over time, but it never
+interprets what an event *means*. All game meaning enters through a **game
+adapter** — the seam defined here. This is the concrete realization of the
+progress-reducer item in
+[ADR 0002](../../../docs/decisions/0002-game-adapter-pattern.md).
+
+## `ReplayAdapter<T>`
+
+An adapter is a plain object supplied at construction:
+
+```js
+new PlaybackClock(envelope, deps, adapter)
+```
+
+```ts
+// Typed generically over the game's event vocabulary T (and state S).
+type ReplayAdapter<T> = {
+  progress?: ProgressReducer<T>
+  state?: StateReducer<T, S>
+}
+
+type ProgressReducer<T>   = (events: MoveEvent<T>[]) => number  // 0–100
+type StateReducer<T, S>   = (events: MoveEvent<T>[]) => S        // full game state
+```
+
+`MoveEvent<T>` is the move-log record `{ seq, t, event, receivedTs? }`, where
+`event` is the game's own payload — opaque to the engine.
+
+## `progress(events) → %`
+
+The only adapter method today. It maps the **ordered slice of events delivered so
+far** (every event whose offset ≤ the current playback position) to a completion
+percentage.
+
+- **Input:** `MoveEvent<T>[]` — the played-so-far slice, in order. To compute a
+  percentage the adapter typically needs a total (e.g. total safe cells); it owns
+  that context, usually by closing over the board it was built from. The engine
+  passes only the slice.
+- **Output:** a number in `[0, 100]`. The engine **clamps** the result into range
+  and throws if the reducer returns a non-number, so an adapter can be permissive.
+- **When:** call `clock.progress()` at any time. It returns `null` if no adapter
+  (or no `progress`) was supplied — the engine never invents a percentage.
+
+```js
+// A minesweeper-style adapter, built over its board (illustrative):
+const adapter = {
+  progress: (events) => {
+    const revealed = events.filter(e => e.event.type === 'reveal').length
+    return (revealed / totalSafeCells) * 100
+  }
+}
+const clock = new PlaybackClock(envelope, {}, adapter)
+clock.seek(1500)
+clock.progress() // → e.g. 42
+```
+
+## `state(events) → S` (full-board mode)
+
+The second reducer reconstructs the **complete game state** at a playback point
+from the ordered slice of events delivered so far. It powers full-board replay —
+rebuilding the whole board on seek, not just a percentage.
+
+- **Input:** `MoveEvent<T>[]` — the played-so-far slice, in order.
+- **Output:** the game's own state type `S` (opaque to the engine). For mnswpr
+  it's a 2D board snapshot: `{ rows, cols, phase, revealedSafe, cells }`.
+- **When:** `clock.state()` returns the current reconstruction, and `onState`
+  streams `{ position, state }` as playback advances or seeks.
+
+### Flag-gated
+
+Full-board mode is **off by default** and gated behind a runtime flag — the
+engine's minimal, documented feature-flag seam:
+
+```js
+new PlaybackClock(envelope, deps, adapter, { fullBoard: true })
+```
+
+When the flag is **off** (default), the mode is fully inert: `state()` returns
+`null`, `onState` never fires, and the state reducer is never invoked (no
+reconstruction cost). When **on** with a `state` reducer supplied, `state()` and
+`onState` reconstruct the board — and `seek(t)` rebuilds the exact state at `t`.
+
+## Contract rules
+
+- **The engine calls the reducer; it never interprets events itself.** Engine
+  source references only envelope types (`MoveEvent` / `MoveLog`) and the log's
+  recording metadata (`seq`, `t`) — never an event's `.event` payload. This is
+  enforced by a guard in `test/playback-clock.test.js`.
+- **The adapter owns all game meaning** — event vocabulary, progress math, and
+  (as the contract grows) state reduction and terminal predicates per ADR 0002.
+- **Typed generically over `T`** so one engine serves every game.

packages/replay/index.js

@@ -0,0 +1,422 @@
+// @ts-check
+import { assertMoveLog, SCHEMA_VERSION } from '@cozy-games/move-log'
+
+/**
+ * `@cozy-games/replay` — the core of a game-agnostic replay engine.
+ *
+ * {@link PlaybackClock} re-drives a move-log envelope over time: it schedules
+ * each recorded event to fire at its OFFSET (its `t` relative to the first
+ * event) as playback time advances, and supports play / pause / seek. It
+ * consumes ONLY the generic envelope (`@cozy-games/move-log`) and never inspects
+ * the inside of an `event` — no game types cross this boundary.
+ *
+ * The clock and scheduler are injected (mirroring the core session's
+ * injected-clock seam), so tests drive it with fake timers or a hand-rolled
+ * scheduler for exact, deterministic timing.
+ */
+
+/**
+ * @typedef {import('@cozy-games/move-log').MoveEvent<any>} Event
+ * @typedef {import('@cozy-games/move-log').MoveLog<any>} Envelope
+ * @typedef {{
+ *   clock?: () => number,
+ *   setTimeout?: (fn: () => void, ms: number) => any,
+ *   clearTimeout?: (handle: any) => void
+ * }} Deps
+ */
+
+/**
+ * A reducer supplied by a game adapter: given the ordered slice of events played
+ * so far (offset <= the current position), return a completion percentage in
+ * `[0, 100]`. Typed generically over the game's event vocabulary `T`. The engine
+ * clamps the result and never inspects an event's payload — all interpretation
+ * lives in this reducer.
+ *
+ * @template T
+ * @typedef {(events: import('@cozy-games/move-log').MoveEvent<T>[]) => number} ProgressReducer
+ */
+
+/**
+ * A reducer supplied by a game adapter for full-board replay: given the ordered
+ * slice of events played so far, reconstruct the complete game state `S` at that
+ * point. Typed generically over the event vocabulary `T` and the (opaque) state
+ * `S`. Powers the flag-gated full-board mode; the engine treats `S` as a black box.
+ *
+ * @template T, S
+ * @typedef {(events: import('@cozy-games/move-log').MoveEvent<T>[]) => S} StateReducer
+ */
+
+/**
+ * The replay game-adapter contract (v0) — the seam through which game meaning
+ * enters the engine. Both methods are optional; the engine calls whichever the
+ * mode needs and never interprets an event itself. See `docs/adapter-interface.md`.
+ *
+ * @template T
+ * @typedef {{ progress?: ProgressReducer<T>, state?: StateReducer<T, any> }} ReplayAdapter
+ */
+
+/**
+ * A version reader: normalize a raw envelope of its generation into the canonical
+ * ordered `MoveEvent` records the engine plays. One engine build can therefore
+ * replay envelopes from multiple format generations.
+ *
+ * @typedef {(envelope: any) => Event[]} EnvelopeReader
+ */
+
+/** v1 is the canonical format itself — its `events` are already the records. */
+function readV1(envelope) {
+  return envelope.events
+}
+
+/**
+ * The built-in dispatch table: `schema_version → reader`. Adding a real future
+ * generation is exactly one entry here (plus its normalizer). Callers can also
+ * supply extra/override readers per instance via the `readers` option.
+ *
+ * @type {Record<number, EnvelopeReader>}
+ */
+const ENVELOPE_READERS = { [SCHEMA_VERSION]: readV1 }
+
+/**
+ * Dispatch on an envelope's `schema_version` to the matching reader and return
+ * the canonical `MoveEvent` records. Unknown/unsupported versions fail LOUDLY
+ * with a specific error — never a silent best-effort parse. Whatever a reader
+ * returns is validated as a canonical move log, so a half-normalized generation
+ * can't reach the engine.
+ *
+ * @param {any} envelope
+ * @param {Record<number, EnvelopeReader>} [extraReaders] - added/overriding readers
+ * @returns {Event[]}
+ */
+export function readEnvelope(envelope, extraReaders) {
+  if (envelope === null || typeof envelope !== 'object') {
+    throw new TypeError(`readEnvelope: expected an envelope object (got ${envelope === null ? 'null' : typeof envelope})`)
+  }
+  const readers = extraReaders ? { ...ENVELOPE_READERS, ...extraReaders } : ENVELOPE_READERS
+  const version = envelope.schema_version
+  const read = readers[version]
+  if (typeof read !== 'function') {
+    const supported = Object.keys(readers).map(Number).sort((a, b) => a - b).join(', ')
+    throw new RangeError(`readEnvelope: unsupported envelope schema_version ${JSON.stringify(version)} (supported: ${supported})`)
+  }
+  const records = read(envelope)
+  // Every reader MUST normalize to canonical move-log records; enforce it here so
+  // no downstream generation can feed the engine a malformed or half-normalized log.
+  assertMoveLog({ schema_version: SCHEMA_VERSION, events: records })
+  return records
+}
+
+export class PlaybackClock {
+  /**
+   * @param {Envelope} envelope - a valid move-log envelope (validated here)
+   * @param {Deps} [deps] - injected time source + scheduler (default: real host)
+   * @param {ReplayAdapter<any>} [adapter] - game adapter (progress / state reducers)
+   * @param {{ fullBoard?: boolean, readers?: Record<number, EnvelopeReader> }} [options] -
+   *   `fullBoard` flag-gates full-board mode (default OFF: `state()`/`onState` are
+   *   inert and the state reducer is never called) — the minimal, documented
+   *   feature-flag seam for this engine. `readers` adds/overrides schema-version
+   *   readers for this instance (see {@link readEnvelope}).
+   */
+  constructor(envelope, deps = {}, adapter = {}, options = {}) {
+    // Dispatch on schema_version → the matching reader's canonical records.
+    const records = readEnvelope(envelope, options.readers)
+    if (adapter.progress !== undefined && typeof adapter.progress !== 'function') {
+      throw new TypeError('PlaybackClock: adapter.progress must be a function when provided')
+    }
+    if (adapter.state !== undefined && typeof adapter.state !== 'function') {
+      throw new TypeError('PlaybackClock: adapter.state must be a function when provided')
+    }
+    this._adapter = adapter
+    this._fullBoard = options.fullBoard === true
+
+    const {
+      clock = () => Date.now(),
+      setTimeout = (fn, ms) => globalThis.setTimeout(fn, ms),
+      clearTimeout = (handle) => globalThis.clearTimeout(handle)
+    } = deps
+    this._now = clock
+    this._setTimeout = setTimeout
+    this._clearTimeout = clearTimeout
+
+    // Sort by recorded time (tie-break by seq) and rebase to offsets so the first
+    // event sits at offset 0 — "recorded offset relative to playback time".
+    const sorted = [...records].sort((a, b) => a.t - b.t || a.seq - b.seq)
+    const baseT = sorted.length ? sorted[0].t : 0
+    /** @type {{ offset: number, record: Event }[]} */
+    this._events = sorted.map(record => ({ offset: record.t - baseT, record }))
+    this._duration = this._events.length ? this._events[this._events.length - 1].offset : 0
+
+    // Playback state. Invariant: `_cursor` === number of events whose offset is
+    // <= the current position; events below the cursor have been delivered in the
+    // current forward pass. This single source of truth makes seek deterministic.
+    this._position = 0
+    this._cursor = 0
+    this._playing = false
+    /** @type {any} */
+    this._timer = null
+    this._anchorClock = 0
+    this._anchorPosition = 0
+    /** @type {Set<(event: Event) => void>} */
+    this._handlers = new Set()
+    /** @type {Set<(update: { position: number, progress: number }) => void>} */
+    this._progressHandlers = new Set()
+    /** Last progress value pushed, so unchanged progress (e.g. a flag) is not re-emitted. */
+    this._lastProgress = /** @type {number | null} */ (null)
+    /** @type {Set<(update: { position: number, state: any }) => void>} */
+    this._stateHandlers = new Set()
+    /** @type {Set<(update: { position: number }) => void>} */
+    this._endHandlers = new Set()
+    /** True once the end has been reached; re-arms when playback moves back before it. */
+    this._ended = false
+  }
+
+  /** Total playback length in ms (offset of the last event; 0 if empty). */
+  get duration() {
+    return this._duration
+  }
+
+  /** @returns {boolean} */
+  isPlaying() {
+    return this._playing
+  }
+
+  /** Current playback position in ms, clamped to `[0, duration]`. */
+  position() {
+    return this._livePosition()
+  }
+
+  /**
+   * Completion percentage (0–100) at the current position, via the adapter's
+   * progress reducer — or `null` if no reducer was supplied. The engine hands the
+   * reducer the ordered slice of events delivered so far and clamps its result;
+   * it never interprets an event payload itself (that's the adapter's job).
+   *
+   * @returns {number | null}
+   */
+  progress() {
+    const reduce = this._adapter.progress
+    if (typeof reduce !== 'function') return null
+    const delivered = this._events.slice(0, this._cursor).map(e => e.record)
+    const pct = reduce(delivered)
+    if (typeof pct !== 'number' || Number.isNaN(pct)) {
+      throw new TypeError(`PlaybackClock.progress: reducer must return a number (got ${typeof pct})`)
+    }
+    return Math.min(100, Math.max(0, pct))
+  }
+
+  /**
+   * Full-board mode: the reconstructed game state at the current position, via the
+   * adapter's `state` reducer over the delivered slice. Returns `null` unless the
+   * `fullBoard` flag is on AND a state reducer was supplied — so the mode is inert
+   * (and the reducer never runs) by default. The state shape `S` is the adapter's;
+   * the engine treats it as opaque.
+   *
+   * @returns {any}
+   */
+  state() {
+    if (!this._fullBoard) return null
+    const reduce = this._adapter.state
+    if (typeof reduce !== 'function') return null
+    return reduce(this._events.slice(0, this._cursor).map(e => e.record))
+  }
+
+  /**
+   * Subscribe to delivered events. The handler receives the raw envelope record
+   * (`{ seq, t, event, ... }`) — the payload stays opaque. Returns an unsubscribe.
+   *
+   * @param {(event: Event) => void} handler
+   * @returns {() => void}
+   */
+  on(handler) {
+    this._handlers.add(handler)
+    return () => this._handlers.delete(handler)
+  }
+
+  /**
+   * Progress-mode subscription: receive `{ position, progress }` updates as
+   * playback advances — the "percent complete over elapsed time" signal. Fires
+   * only when the percentage actually changes (so flags/unflags, which don't
+   * advance progress, emit nothing), on play, seek forward, and seek backward.
+   * Requires an adapter with a `progress` reducer; without one it never emits.
+   * Subscribe before playing to catch every update; use {@link progress} for the
+   * current value at any time. Returns an unsubscribe.
+   *
+   * @param {(update: { position: number, progress: number }) => void} handler
+   * @returns {() => void}
+   */
+  onProgress(handler) {
+    this._progressHandlers.add(handler)
+    return () => this._progressHandlers.delete(handler)
+  }
+
+  /**
+   * Full-board mode subscription: receive `{ position, state }` whenever the
+   * delivered set changes (play, seek forward, seek backward), where `state` is
+   * the adapter's reconstruction at that position. Inert unless the `fullBoard`
+   * flag is on and a state reducer was supplied. Returns an unsubscribe.
+   *
+   * @param {(update: { position: number, state: any }) => void} handler
+   * @returns {() => void}
+   */
+  onState(handler) {
+    this._stateHandlers.add(handler)
+    return () => this._stateHandlers.delete(handler)
+  }
+
+  /**
+   * Subscribe to the "ended" signal: fires with `{ position }` when playback
+   * reaches the last recorded event's offset — the SAME signal whether the run
+   * completed or the recording was truncated mid-game (the engine has no notion
+   * of a terminal event). Fires once on reaching the end and re-arms if playback
+   * moves back before it. Returns an unsubscribe.
+   *
+   * @param {(update: { position: number }) => void} handler
+   * @returns {() => void}
+   */
+  onEnd(handler) {
+    this._endHandlers.add(handler)
+    return () => this._endHandlers.delete(handler)
+  }
+
+  /**
+   * Start (or resume) playback from the current position. Any event already due
+   * at the current position fires synchronously; the rest are scheduled at their
+   * offsets. No-op if already playing or already at the end.
+   */
+  play() {
+    if (this._playing) return
+    this._playing = true
+    this._anchorClock = this._now()
+    this._anchorPosition = this._position
+    this._scheduleNext()
+  }
+
+  /** Pause playback, freezing the position where it currently is. */
+  pause() {
+    if (!this._playing) return
+    this._position = this._livePosition()
+    this._playing = false
+    this._clearTimer()
+  }
+
+  /**
+   * Seek to playback time `t` (ms, clamped to `[0, duration]`). Deterministic:
+   * afterwards the delivered set is exactly the events at offset <= t. Moving
+   * forward delivers the newly-passed events in order (each exactly once); moving
+   * backward rewinds the cursor without delivering, so a later forward pass
+   * re-delivers them. Re-schedules if playing.
+   *
+   * @param {number} t
+   */
+  seek(t) {
+    if (typeof t !== 'number' || Number.isNaN(t)) {
+      throw new TypeError(`PlaybackClock.seek: t must be a number (got ${typeof t})`)
+    }
+    const wasPlaying = this._playing
+    this._clearTimer()
+    this._advanceTo(t)
+    if (wasPlaying) {
+      this._anchorClock = this._now()
+      this._anchorPosition = this._position
+      this._scheduleNext()
+    }
+  }
+
+  // ---- internals ----
+
+  /** Live position: derived from the clock while playing, else the stored value. */
+  _livePosition() {
+    if (!this._playing) return this._position
+    const raw = this._anchorPosition + (this._now() - this._anchorClock)
+    return Math.min(Math.max(raw, 0), this._duration)
+  }
+
+  /**
+   * Move the cursor to match `target` position: emit events crossed going
+   * forward (once each), un-count events going backward (no emit). Sets position.
+   * @param {number} target
+   */
+  _advanceTo(target) {
+    const t = Math.min(Math.max(target, 0), this._duration)
+    const before = this._cursor
+    while (this._cursor < this._events.length && this._events[this._cursor].offset <= t) {
+      this._emit(this._events[this._cursor].record)
+      this._cursor++
+    }
+    while (this._cursor > 0 && this._events[this._cursor - 1].offset > t) {
+      this._cursor--
+    }
+    this._position = t
+    this._emitProgressIfChanged()
+    if (this._cursor !== before) this._emitState()
+    this._maybeEmitEnded()
+  }
+
+  /** Deliver an event to all subscribers. */
+  _emit(record) {
+    for (const handler of this._handlers) handler(record)
+  }
+
+  /** Push a progress update to subscribers, but only when the percentage moved. */
+  _emitProgressIfChanged() {
+    if (this._progressHandlers.size === 0) return
+    const progress = this.progress()
+    if (progress === null || progress === this._lastProgress) return
+    this._lastProgress = progress
+    const update = { position: this._position, progress }
+    for (const handler of this._progressHandlers) handler(update)
+  }
+
+  /**
+   * Fire "ended" once when every recorded event has been delivered (the timeline
+   * reached the last event's offset); re-arm when playback moves back before it.
+   * Terminal-agnostic: a truncated recording ends here exactly like a complete one.
+   */
+  _maybeEmitEnded() {
+    const atEnd = this._events.length > 0 && this._cursor >= this._events.length
+    if (atEnd && !this._ended) {
+      this._ended = true
+      const update = { position: this._position }
+      for (const handler of this._endHandlers) handler(update)
+    } else if (!atEnd) {
+      this._ended = false
+    }
+  }
+
+  /** Push a reconstructed board state to subscribers — only in active full-board mode. */
+  _emitState() {
+    if (!this._fullBoard || this._stateHandlers.size === 0) return
+    if (typeof this._adapter.state !== 'function') return
+    const update = { position: this._position, state: this.state() }
+    for (const handler of this._stateHandlers) handler(update)
+  }
+
+  /**
+   * Deliver anything already due, then arm a timer for the next pending event.
+   * Ends playback when the cursor reaches the last event.
+   */
+  _scheduleNext() {
+    this._clearTimer()
+    if (!this._playing) return
+    this._advanceTo(this._livePosition())
+    if (this._cursor >= this._events.length) {
+      this._position = this._duration
+      this._playing = false
+      return
+    }
+    const delay = Math.max(0, this._events[this._cursor].offset - this._livePosition())
+    this._timer = this._setTimeout(() => this._onTimer(), delay)
+  }
+
+  _onTimer() {
+    this._timer = null
+    if (this._playing) this._scheduleNext()
+  }
+
+  _clearTimer() {
+    if (this._timer !== null) {
+      this._clearTimeout(this._timer)
+      this._timer = null
+    }
+  }
+}

packages/replay/package.json

@@ -0,0 +1,25 @@
+{
+  "name": "@cozy-games/replay",
+  "version": "0.0.1",
+  "description": "Game-agnostic replay engine — a playback clock (play/pause/seek + event scheduling) that re-drives a move-log envelope over time",
+  "author": "Ayo Ayco",
+  "private": true,
+  "type": "module",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/ayo-run/mnswpr"
+  },
+  "main": "index.js",
+  "exports": {
+    ".": {
+      "default": "./index.js"
+    },
+    "./*": {
+      "default": "./*"
+    }
+  },
+  "dependencies": {
+    "@cozy-games/move-log": "workspace:*"
+  },
+  "license": "BSD-2-Clause"
+}

packages/replay/test/full-board-mode.test.js

@@ -0,0 +1,147 @@
+// @ts-check
+import { describe, it, expect } from 'vitest'
+import { PlaybackClock } from '@cozy-games/replay'
+import { createMoveLog } from '@cozy-games/move-log'
+
+// Real mnswpr run + state reducer — imported by the TEST (relative), so no game
+// dependency enters the engine's manifest.
+import { GameSession, MinesweeperRules } from '../../mnswpr/core/index.js'
+import { createStateReducer } from '../../mnswpr/adapters/replay-state.js'
+
+function fakeScheduler(start = 0) {
+  let now = start
+  let nextId = 1
+  const timers = new Map()
+  return {
+    clock: () => now,
+    setTimeout: (fn, ms) => {
+      const id = nextId++
+      timers.set(id, { at: now + Math.max(0, ms), fn })
+      return id
+    },
+    clearTimeout: (id) => { timers.delete(id) },
+    advance(ms) {
+      const target = now + ms
+      for (;;) {
+        let due = null
+        for (const [id, timer] of timers) {
+          if (timer.at <= target && (due === null || timer.at < due.at)) due = { id, ...timer }
+        }
+        if (!due) break
+        timers.delete(due.id)
+        now = due.at
+        due.fn()
+      }
+      now = target
+    }
+  }
+}
+
+const board = {
+  rows: 3,
+  cols: 3,
+  mines: 1,
+  cells: [
+    [{ mine: true, adjacent: 0 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 1 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }]
+  ],
+  mineLocations: [[0, 0]]
+}
+
+// Record a real run: reveal, reveal, flag the mine, then flood the rest.
+let nowClock = 0
+const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(board), clock: () => nowClock })
+const emitted = []
+session.onMove(e => emitted.push(e))
+const baseT = 1000
+for (const step of [
+  { at: 1000, move: { type: 'reveal', r: 0, c: 1 } },
+  { at: 1100, move: { type: 'reveal', r: 1, c: 0 } },
+  { at: 1200, move: { type: 'flag', r: 0, c: 0 } },
+  { at: 1300, move: { type: 'reveal', r: 2, c: 2 } }
+]) {
+  nowClock = step.at
+  session.applyMove(step.move)
+}
+const records = emitted.map(e => ({ seq: e.seq, t: e.t, event: e }))
+const envelope = createMoveLog(records)
+const reduce = createStateReducer(board)
+
+// Independent ground truth: reduce over records at offset <= t.
+const truth = t => reduce(records.filter(r => (r.t - baseT) <= t))
+
+describe('full-board mode — flag gating (inert by default)', () => {
+  it('does nothing when the flag is off, even with a state reducer', () => {
+    const clock = new PlaybackClock(envelope, fakeScheduler(), { state: reduce })
+    const updates = []
+    clock.onState(u => updates.push(u))
+    clock.seek(clock.duration)
+    expect(clock.state()).toBe(null)
+    expect(updates).toEqual([])
+  })
+
+  it('is inert when the flag is on but no state reducer is supplied', () => {
+    const clock = new PlaybackClock(envelope, fakeScheduler(), {}, { fullBoard: true })
+    clock.seek(clock.duration)
+    expect(clock.state()).toBe(null)
+  })
+})
+
+describe('full-board mode — reconstruction (flag on)', () => {
+  const make = () => new PlaybackClock(envelope, fakeScheduler(), { state: reduce }, { fullBoard: true })
+
+  it('state() reconstructs the board at multiple seek points', () => {
+    const clock = make()
+    for (const t of [-5, 0, 50, 100, 150, 200, 300, 400]) {
+      clock.seek(t)
+      const clamped = Math.max(0, Math.min(t, clock.duration))
+      expect(clock.state()).toEqual(truth(clamped))
+    }
+  })
+
+  it('seek reconstructs the correct concrete state (forward then backward)', () => {
+    const clock = make()
+
+    clock.seek(clock.duration) // end
+    let b = clock.state()
+    expect(b.phase).toBe('won')
+    expect(b.revealedSafe).toBe(8)
+    expect(b.cells[0][0].status).toBe('flagged')
+
+    clock.seek(100) // back to just after the two opening reveals
+    b = clock.state()
+    expect(b.phase).toBe('active')
+    expect(b.revealedSafe).toBe(2)
+    expect(b.cells[0][1].status).toBe('revealed')
+    expect(b.cells[2][2].status).toBe('hidden')
+
+    clock.seek(0) // back to the very first reveal
+    expect(clock.state().revealedSafe).toBe(1)
+  })
+
+  it('onState streams a reconstruction on every delivery (incl. the flag)', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope, s, { state: reduce }, { fullBoard: true })
+    const updates = []
+    clock.onState(u => updates.push(u))
+    clock.play()
+    s.advance(400)
+    expect(updates.map(u => u.position)).toEqual([0, 100, 200, 300])
+    expect(updates.at(-1).state.phase).toBe('won')
+  })
+
+  it('onState fires on backward seek', () => {
+    const clock = make()
+    const updates = []
+    clock.onState(u => updates.push(u))
+    clock.seek(clock.duration) // forward (delivers all at once → 1 update)
+    clock.seek(0)              // backward → 1 update
+    expect(updates).toHaveLength(2)
+    expect(updates.at(-1).state.revealedSafe).toBe(1)
+  })
+
+  it('rejects a non-function state reducer at construction', () => {
+    expect(() => new PlaybackClock(envelope, fakeScheduler(), { state: /** @type {any} */ (5) })).toThrow(TypeError)
+  })
+})

packages/replay/test/partial-logs.test.js

@@ -0,0 +1,174 @@
+// @ts-check
+import { describe, it, expect } from 'vitest'
+import { PlaybackClock } from '@cozy-games/replay'
+import { createMoveLog } from '@cozy-games/move-log'
+
+// Real mnswpr run + reducers — imported by the TEST (relative), so no game
+// dependency enters the engine's manifest.
+import { GameSession, MinesweeperRules } from '../../mnswpr/core/index.js'
+import { createProgressReducer } from '../../mnswpr/adapters/replay-progress.js'
+import { createStateReducer } from '../../mnswpr/adapters/replay-state.js'
+
+function fakeScheduler(start = 0) {
+  let now = start
+  let nextId = 1
+  const timers = new Map()
+  return {
+    clock: () => now,
+    setTimeout: (fn, ms) => {
+      const id = nextId++
+      timers.set(id, { at: now + Math.max(0, ms), fn })
+      return id
+    },
+    clearTimeout: (id) => { timers.delete(id) },
+    advance(ms) {
+      const target = now + ms
+      for (;;) {
+        let due = null
+        for (const [id, timer] of timers) {
+          if (timer.at <= target && (due === null || timer.at < due.at)) due = { id, ...timer }
+        }
+        if (!due) break
+        timers.delete(due.id)
+        now = due.at
+        due.fn()
+      }
+      now = target
+    }
+  }
+}
+
+const board = () => ({
+  rows: 3,
+  cols: 3,
+  mines: 1,
+  cells: [
+    [{ mine: true, adjacent: 0 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 1 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }]
+  ],
+  mineLocations: [[0, 0]]
+})
+
+// A TRUNCATED recording: two opening reveals, then the log just stops — the game
+// is still 'active' (2 of 8 safe cells), no win/loss ever recorded.
+function truncatedEnvelope() {
+  let now = 0
+  const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(board()), clock: () => now })
+  const emitted = []
+  session.onMove(e => emitted.push(e))
+  now = 1000; session.applyMove({ type: 'reveal', r: 0, c: 1 })
+  now = 1200; session.applyMove({ type: 'reveal', r: 1, c: 0 })
+  // ...stream cut here — no terminal event.
+  const baseT = 1000
+  return {
+    envelope: createMoveLog(emitted.map(e => ({ seq: e.seq, t: e.t, event: e }))),
+    lastOffset: 1200 - baseT // 200
+  }
+}
+
+describe('partial/incomplete recordings — progress mode', () => {
+  it('replays to the last event without error and freezes progress (no jump to 100%)', () => {
+    const { envelope, lastOffset } = truncatedEnvelope()
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope, s, { progress: createProgressReducer(board()) })
+
+    const progressUpdates = []
+    const ends = []
+    clock.onProgress(u => progressUpdates.push(u))
+    clock.onEnd(u => ends.push(u))
+
+    expect(() => { clock.play(); s.advance(10_000) }).not.toThrow() // long past the last event
+
+    // Frozen at the true value for 2/8 safe cells — NOT extrapolated to 100.
+    expect(clock.progress()).toBeCloseTo(25, 5)
+    expect(clock.isPlaying()).toBe(false)
+
+    // "ended" fired once, at the last event's offset.
+    expect(ends).toHaveLength(1)
+    expect(ends[0].position).toBe(lastOffset)
+
+    // Progress held at its last value after the stream ended.
+    expect(progressUpdates.at(-1).progress).toBeCloseTo(25, 5)
+  })
+
+  it('progress stays frozen when time advances past the end', () => {
+    const { envelope } = truncatedEnvelope()
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope, s, { progress: createProgressReducer(board()) })
+    clock.play()
+    s.advance(300)
+    const atEnd = clock.progress()
+    s.advance(5000) // way past
+    expect(clock.progress()).toBe(atEnd) // no drift, no extrapolation
+    expect(atEnd).toBeCloseTo(25, 5)
+  })
+})
+
+describe('partial/incomplete recordings — full-board mode', () => {
+  it('reconstructs the last recorded state without error and ends cleanly', () => {
+    const { envelope, lastOffset } = truncatedEnvelope()
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope, s, { state: createStateReducer(board()) }, { fullBoard: true })
+    const ends = []
+    clock.onEnd(u => ends.push(u))
+
+    expect(() => { clock.play(); s.advance(10_000) }).not.toThrow()
+
+    const b = clock.state()
+    expect(b.phase).toBe('active') // never reached a terminal state — and that's fine
+    expect(b.revealedSafe).toBe(2)
+    expect(b.cells[0][1].status).toBe('revealed')
+    expect(b.cells[2][2].status).toBe('hidden') // rest still unopened
+
+    expect(ends).toHaveLength(1)
+    expect(ends[0].position).toBe(lastOffset)
+  })
+})
+
+describe('the "ended" signal', () => {
+  it('fires identically for a complete run and a truncated one', () => {
+    // Complete run: play the board to a win.
+    let now = 0
+    const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(board()), clock: () => now })
+    const emitted = []
+    session.onMove(e => emitted.push(e))
+    now = 1000; session.applyMove({ type: 'reveal', r: 2, c: 2 }) // floods all 8 → won
+    const complete = createMoveLog(emitted.map(e => ({ seq: e.seq, t: e.t, event: e })))
+
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(complete, s)
+    const ends = []
+    clock.onEnd(u => ends.push(u))
+    clock.play()
+    s.advance(1000)
+    expect(ends).toHaveLength(1)
+    expect(ends[0].position).toBe(clock.duration) // last event's offset
+  })
+
+  it('fires on seek to the end and re-arms after seeking back', () => {
+    const { envelope } = truncatedEnvelope()
+    const clock = new PlaybackClock(envelope, fakeScheduler())
+    const ends = []
+    clock.onEnd(() => ends.push(1))
+
+    clock.seek(clock.duration) // reach the end
+    expect(ends).toHaveLength(1)
+
+    clock.seek(clock.duration) // still at the end — no re-fire
+    expect(ends).toHaveLength(1)
+
+    clock.seek(0)              // move back — re-arm
+    clock.seek(clock.duration) // reach the end again
+    expect(ends).toHaveLength(2)
+  })
+
+  it('does not fire for an empty envelope', () => {
+    const clock = new PlaybackClock(createMoveLog([]), fakeScheduler())
+    const ends = []
+    clock.onEnd(() => ends.push(1))
+    clock.play()
+    clock.seek(0)
+    expect(ends).toEqual([])
+  })
+})

packages/replay/test/playback-clock.test.js

@@ -0,0 +1,323 @@
+// @ts-check
+import { describe, it, expect, vi, afterEach } from 'vitest'
+import { readFileSync, readdirSync, statSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { dirname, join } from 'node:path'
+
+// Imported via the PACKAGE NAME to prove the new workspace module resolves.
+import { PlaybackClock } from '@cozy-games/replay'
+import { createMoveLog } from '@cozy-games/move-log'
+
+/**
+ * A hand-rolled deterministic scheduler — the injected-clock seam in action, with
+ * zero reliance on vi internals. `advance(ms)` fires due timers in time order,
+ * picking up timers scheduled from within a firing callback.
+ */
+function fakeScheduler(start = 0) {
+  let now = start
+  let nextId = 1
+  const timers = new Map()
+  return {
+    clock: () => now,
+    setTimeout: (fn, ms) => {
+      const id = nextId++
+      timers.set(id, { at: now + Math.max(0, ms), fn })
+      return id
+    },
+    clearTimeout: (id) => { timers.delete(id) },
+    advance(ms) {
+      const target = now + ms
+      for (;;) {
+        let due = null
+        for (const [id, timer] of timers) {
+          if (timer.at <= target && (due === null || timer.at < due.at)) due = { id, ...timer }
+        }
+        if (!due) break
+        timers.delete(due.id)
+        now = due.at
+        due.fn()
+      }
+      now = target
+    }
+  }
+}
+
+// Events at offsets 0, 100, 350 (t rebased from 1000). Payload is opaque to the clock.
+function envelope() {
+  return createMoveLog([
+    { seq: 1, t: 1000, event: { type: 'reveal', r: 0, c: 0 } },
+    { seq: 2, t: 1100, event: { type: 'flag', r: 1, c: 2 } },
+    { seq: 3, t: 1350, event: { type: 'chord', r: 4, c: 4 } }
+  ])
+}
+
+const typesOf = records => records.map(r => r.event.type)
+
+describe('PlaybackClock — construction & shape', () => {
+  it('rebases to offsets: duration is the last offset, first event at 0', () => {
+    const clock = new PlaybackClock(envelope(), fakeScheduler())
+    expect(clock.duration).toBe(350)
+    expect(clock.position()).toBe(0)
+    expect(clock.isPlaying()).toBe(false)
+  })
+
+  it('validates the envelope (rejects a non-envelope)', () => {
+    expect(() => new PlaybackClock(/** @type {any} */ (null))).toThrow()
+    expect(() => new PlaybackClock(/** @type {any} */ ({ schema_version: 2, events: [] }))).toThrow()
+  })
+
+  it('handles an empty envelope gracefully', () => {
+    const clock = new PlaybackClock(createMoveLog([]), fakeScheduler())
+    const seen = []
+    clock.on(r => seen.push(r))
+    expect(clock.duration).toBe(0)
+    clock.play()
+    expect(clock.isPlaying()).toBe(false) // nothing to play → ends immediately
+    expect(seen).toEqual([])
+  })
+})
+
+describe('PlaybackClock — play / pause with an injected scheduler', () => {
+  it('fires events at their recorded offsets, exactly', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope(), s)
+    const seen = []
+    clock.on(r => seen.push({ type: r.event.type, at: s.clock() }))
+
+    clock.play()
+    // offset-0 event fires synchronously on play
+    expect(seen).toEqual([{ type: 'reveal', at: 0 }])
+
+    s.advance(100)
+    expect(seen[1]).toEqual({ type: 'flag', at: 100 })
+
+    s.advance(250) // reach offset 350
+    expect(seen[2]).toEqual({ type: 'chord', at: 350 })
+    expect(clock.isPlaying()).toBe(false) // ended
+    expect(clock.position()).toBe(350)
+  })
+
+  it('pause freezes position and stops delivery', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope(), s)
+    const seen = []
+    clock.on(r => seen.push(r.event.type))
+
+    clock.play()
+    s.advance(150) // past offset 100, between 100 and 350
+    clock.pause()
+    expect(clock.position()).toBe(150)
+    expect(seen).toEqual(['reveal', 'flag'])
+
+    s.advance(1000) // no timers should fire while paused
+    expect(seen).toEqual(['reveal', 'flag'])
+    expect(clock.position()).toBe(150)
+  })
+
+  it('resumes from the paused position', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope(), s)
+    const seen = []
+    clock.on(r => seen.push({ type: r.event.type, at: s.clock() }))
+
+    clock.play()
+    s.advance(150)
+    clock.pause()
+    clock.play() // resume at 150; next event at 350 ⇒ 200ms away
+    s.advance(200)
+    expect(seen.map(e => e.type)).toEqual(['reveal', 'flag', 'chord'])
+    expect(seen[2].at).toBe(350) // still fires at its true offset
+  })
+})
+
+describe('PlaybackClock — seek determinism', () => {
+  it('seek forward delivers exactly the events at offset <= t, in order, once', () => {
+    const clock = new PlaybackClock(envelope(), fakeScheduler())
+    const seen = []
+    clock.on(r => seen.push(r))
+
+    clock.seek(200) // offsets 0 and 100 are <= 200; 350 is not
+    expect(typesOf(seen)).toEqual(['reveal', 'flag'])
+    expect(clock.position()).toBe(200)
+
+    clock.seek(200) // no movement ⇒ no new deliveries
+    expect(typesOf(seen)).toEqual(['reveal', 'flag'])
+  })
+
+  it('seek boundary is inclusive (offset === t fires)', () => {
+    const clock = new PlaybackClock(envelope(), fakeScheduler())
+    const seen = []
+    clock.on(r => seen.push(r))
+    clock.seek(100)
+    expect(typesOf(seen)).toEqual(['reveal', 'flag']) // offset 100 included
+  })
+
+  it('seek backward re-schedules with no duplicate or dropped events', () => {
+    const clock = new PlaybackClock(envelope(), fakeScheduler())
+    const seen = []
+    clock.on(r => seen.push(r))
+
+    clock.seek(400) // deliver all three
+    expect(typesOf(seen)).toEqual(['reveal', 'flag', 'chord'])
+
+    clock.seek(50) // rewind — no delivery; only offset-0 stays "passed"
+    expect(typesOf(seen)).toEqual(['reveal', 'flag', 'chord']) // unchanged
+
+    clock.seek(400) // forward again re-delivers the re-crossed events, once each
+    expect(typesOf(seen)).toEqual(['reveal', 'flag', 'chord', 'flag', 'chord'])
+  })
+
+  it('seek while playing re-anchors and keeps firing correctly', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope(), s)
+    const seen = []
+    clock.on(r => seen.push(r.event.type))
+
+    clock.play()
+    s.advance(50) // only offset-0 delivered so far
+    expect(seen).toEqual(['reveal'])
+
+    clock.seek(120) // jump forward while playing ⇒ deliver offset-100 event
+    expect(seen).toEqual(['reveal', 'flag'])
+
+    s.advance(230) // reach 350 ⇒ final event
+    expect(seen).toEqual(['reveal', 'flag', 'chord'])
+    expect(clock.isPlaying()).toBe(false)
+  })
+
+  it('never delivers an event twice within a single forward pass', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope(), s)
+    const seqs = []
+    clock.on(r => seqs.push(r.seq))
+    clock.play()
+    s.advance(1000)
+    expect(seqs).toEqual([1, 2, 3]) // each once, in order
+  })
+})
+
+describe('PlaybackClock — with vi fake timers', () => {
+  afterEach(() => { vi.useRealTimers() })
+
+  it('play/pause/seek work under vi.useFakeTimers()', () => {
+    vi.useFakeTimers()
+    vi.setSystemTime(0)
+    // Default deps ⇒ Date.now + global setTimeout, both faked by vi.
+    const clock = new PlaybackClock(envelope())
+    const seen = []
+    clock.on(r => seen.push(r.event.type))
+
+    clock.play()
+    expect(seen).toEqual(['reveal']) // offset 0 immediate
+    vi.advanceTimersByTime(100)
+    expect(seen).toEqual(['reveal', 'flag'])
+    clock.pause()
+    vi.advanceTimersByTime(1000)
+    expect(seen).toEqual(['reveal', 'flag']) // paused ⇒ frozen
+    clock.play()
+    vi.advanceTimersByTime(250)
+    expect(seen).toEqual(['reveal', 'flag', 'chord'])
+  })
+})
+
+describe('PlaybackClock — progress reducer (adapter seam)', () => {
+  /**
+   * A dummy adapter defined HERE, in the test — the engine interprets nothing.
+   * @typedef {{ type: string }} DummyEvent
+   * @type {import('@cozy-games/replay').ProgressReducer<DummyEvent>}
+   */
+  const byCount = events => (events.length / 3) * 100 // 3 = total in envelope()
+
+  it('runs against a dummy adapter: progress reflects the delivered slice', () => {
+    const clock = new PlaybackClock(envelope(), fakeScheduler(), { progress: byCount })
+    expect(clock.progress()).toBe(0) // nothing delivered yet
+
+    clock.seek(0) // offset-0 event delivered ⇒ 1/3
+    expect(clock.progress()).toBeCloseTo(33.333, 2)
+
+    clock.seek(100) // 2/3
+    expect(clock.progress()).toBeCloseTo(66.667, 2)
+
+    clock.seek(400) // all 3 ⇒ 100
+    expect(clock.progress()).toBe(100)
+
+    clock.seek(50) // rewind ⇒ back to 1/3
+    expect(clock.progress()).toBeCloseTo(33.333, 2)
+  })
+
+  it('advances as playback advances', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope(), s, { progress: byCount })
+    clock.play()
+    expect(clock.progress()).toBeCloseTo(33.333, 2) // offset-0 fired on play
+    s.advance(100)
+    expect(clock.progress()).toBeCloseTo(66.667, 2)
+    s.advance(250)
+    expect(clock.progress()).toBe(100)
+  })
+
+  it('returns null when no adapter (or no progress reducer) is supplied', () => {
+    expect(new PlaybackClock(envelope(), fakeScheduler()).progress()).toBe(null)
+    expect(new PlaybackClock(envelope(), fakeScheduler(), {}).progress()).toBe(null)
+  })
+
+  it('clamps the reducer output into [0, 100]', () => {
+    const over = new PlaybackClock(envelope(), fakeScheduler(), { progress: () => 999 })
+    const under = new PlaybackClock(envelope(), fakeScheduler(), { progress: () => -50 })
+    expect(over.progress()).toBe(100)
+    expect(under.progress()).toBe(0)
+  })
+
+  it('throws if the reducer returns a non-number', () => {
+    const clock = new PlaybackClock(envelope(), fakeScheduler(), { progress: () => /** @type {any} */ ('nope') })
+    expect(() => clock.progress()).toThrow(TypeError)
+  })
+
+  it('rejects a non-function progress at construction', () => {
+    expect(() => new PlaybackClock(envelope(), fakeScheduler(), { progress: /** @type {any} */ (42) })).toThrow(TypeError)
+  })
+})
+
+describe('game-agnosticism guard (envelope only, no game imports)', () => {
+  const pkgDir = join(dirname(fileURLToPath(import.meta.url)), '..')
+  const GAME_REFERENCES = /mnswpr|minesweeper/i
+
+  it('engine never interprets an event payload (no `.event` access in engine source)', () => {
+    const offenders = []
+    walk(pkgDir, file => {
+      if (!file.endsWith('.js') || file.includes('/test/')) return
+      const code = readFileSync(file, 'utf8')
+        .replace(/\/\*[\s\S]*?\*\//g, '')
+        .replace(/\/\/.*$/gm, '')
+      if (/\.event\b/.test(code)) offenders.push(file)
+    })
+    expect(offenders).toEqual([]) // engine references only envelope metadata (seq/t) + opaque records
+  })
+
+  it('manifest depends only on the envelope, never a game package', () => {
+    const pkg = JSON.parse(readFileSync(join(pkgDir, 'package.json'), 'utf8'))
+    const deps = { ...pkg.dependencies, ...pkg.devDependencies, ...pkg.peerDependencies }
+    expect(Object.keys(deps).filter(name => GAME_REFERENCES.test(name))).toEqual([])
+  })
+
+  it('no source file imports or references a game package', () => {
+    const offenders = []
+    walk(pkgDir, file => {
+      if (!file.endsWith('.js') || file.includes('/test/')) return
+      const code = readFileSync(file, 'utf8')
+        .replace(/\/\*[\s\S]*?\*\//g, '')
+        .replace(/\/\/.*$/gm, '')
+      if (GAME_REFERENCES.test(code)) offenders.push(file)
+    })
+    expect(offenders).toEqual([])
+  })
+})
+
+function walk(dir, fn) {
+  for (const name of readdirSync(dir)) {
+    if (name === 'node_modules') continue
+    const p = join(dir, name)
+    if (statSync(p).isDirectory()) walk(p, fn)
+    else fn(p)
+  }
+}

packages/replay/test/progress-mode.test.js

@@ -0,0 +1,184 @@
+// @ts-check
+import { describe, it, expect } from 'vitest'
+import { PlaybackClock } from '@cozy-games/replay'
+import { createMoveLog } from '@cozy-games/move-log'
+
+// A real mnswpr run + its reducer — imported by the TEST via relative paths, so
+// no game dependency enters the replay engine's manifest.
+import { GameSession, MinesweeperRules } from '../../mnswpr/core/index.js'
+import { createProgressReducer } from '../../mnswpr/adapters/replay-progress.js'
+
+/** Deterministic injected scheduler (the injected-clock seam), no vi needed. */
+function fakeScheduler(start = 0) {
+  let now = start
+  let nextId = 1
+  const timers = new Map()
+  return {
+    clock: () => now,
+    setTimeout: (fn, ms) => {
+      const id = nextId++
+      timers.set(id, { at: now + Math.max(0, ms), fn })
+      return id
+    },
+    clearTimeout: (id) => { timers.delete(id) },
+    advance(ms) {
+      const target = now + ms
+      for (;;) {
+        let due = null
+        for (const [id, timer] of timers) {
+          if (timer.at <= target && (due === null || timer.at < due.at)) due = { id, ...timer }
+        }
+        if (!due) break
+        timers.delete(due.id)
+        now = due.at
+        due.fn()
+      }
+      now = target
+    }
+  }
+}
+
+// 3x3, single mine at (0,0). Total safe = 8.
+const layout = () => ({
+  rows: 3,
+  cols: 3,
+  mines: 1,
+  cells: [
+    [{ mine: true, adjacent: 0 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 1 }, { mine: false, adjacent: 1 }, { mine: false, adjacent: 0 }],
+    [{ mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }, { mine: false, adjacent: 0 }]
+  ],
+  mineLocations: [[0, 0]]
+})
+
+// Drive a real session, recording BOTH the emitted move-events and the ground
+// truth (revealedSafe) after each move — an independent source of truth.
+const board = layout()
+const TOTAL_SAFE = 8
+const session = new GameSession(MinesweeperRules, { state: MinesweeperRules.fromLayout(board), clock: () => nowClock })
+let nowClock = 0
+const emitted = []
+session.onMove(e => emitted.push(e))
+const truthPoints = [] // { offset, revealedSafe } after each move
+
+const script = [
+  { at: 1000, move: { type: 'reveal', r: 0, c: 1 } }, // +1 safe cell
+  { at: 1100, move: { type: 'reveal', r: 1, c: 0 } }, // +1 safe cell
+  { at: 1200, move: { type: 'flag', r: 0, c: 0 } },   // flag the mine — no progress
+  { at: 1300, move: { type: 'reveal', r: 2, c: 2 } }  // floods the rest → all 8
+]
+const baseT = script[0].at
+for (const step of script) {
+  nowClock = step.at
+  session.applyMove(step.move)
+  truthPoints.push({ offset: step.at - baseT, revealedSafe: session.state.revealedSafe })
+}
+
+const records = emitted.map(e => ({ seq: e.seq, t: e.t, event: e }))
+const envelope = createMoveLog(records)
+
+// Ground truth for the mnswpr reducer: revealedSafe / total at a given offset —
+// derived from the session, NOT from the reducer under test.
+function mnswprTruth(offset) {
+  let revealedSafe = 0
+  for (const p of truthPoints) if (p.offset <= offset) revealedSafe = p.revealedSafe
+  return (revealedSafe / TOTAL_SAFE) * 100
+}
+
+// A second, unrelated adapter: percent of events delivered. Ground truth is the
+// count of records at offset <= t.
+const totalEvents = records.length
+const dummyReduce = events => (events.length / totalEvents) * 100
+function dummyTruth(offset) {
+  return (records.filter(r => (r.t - baseT) <= offset).length / totalEvents) * 100
+}
+
+const CASES = [
+  { name: 'mnswpr percent-cleared', adapter: { progress: createProgressReducer(board) }, truth: mnswprTruth },
+  { name: 'dummy percent-of-events', adapter: { progress: dummyReduce }, truth: dummyTruth }
+]
+
+describe.each(CASES)('progress mode — same code path, adapter: $name', ({ adapter, truth }) => {
+  const clamp = t => Math.max(0, Math.min(t, envelope.events[envelope.events.length - 1].t - baseT))
+
+  it('progress() matches the source run at multiple points (via seek)', () => {
+    const clock = new PlaybackClock(envelope, fakeScheduler(), adapter)
+    for (const t of [-10, 0, 50, 100, 150, 200, 250, 300, 400]) {
+      clock.seek(t)
+      expect(clock.progress()).toBeCloseTo(truth(clamp(t)), 5)
+    }
+  })
+
+  it('progress() matches the source run while playing (fake timers)', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope, s, adapter)
+    const updates = []
+    clock.onProgress(u => updates.push(u))
+    clock.play()
+
+    let last = 0
+    for (const cp of [0, 100, 200, 300]) {
+      s.advance(cp - last)
+      last = cp
+      expect(clock.progress()).toBeCloseTo(truth(cp), 5)
+    }
+    expect(clock.progress()).toBeCloseTo(truth(clock.duration), 5)
+
+    // The pushed signal is non-decreasing during forward play and ends at 100.
+    const vals = updates.map(u => u.progress)
+    expect(vals).toEqual([...vals].sort((a, b) => a - b))
+    expect(vals.at(-1)).toBeCloseTo(truth(clock.duration), 5)
+    // Each emitted update matches ground truth at the position it reports.
+    for (const u of updates) expect(u.progress).toBeCloseTo(truth(u.position), 5)
+  })
+
+  it('seek forward and backward move the progress signal correctly', () => {
+    const clock = new PlaybackClock(envelope, fakeScheduler(), adapter)
+    const vals = []
+    clock.onProgress(u => vals.push(u.progress))
+
+    clock.seek(clock.duration) // forward to the end
+    expect(clock.progress()).toBeCloseTo(truth(clock.duration), 5)
+
+    clock.seek(0) // jump back to the start
+    expect(clock.progress()).toBeCloseTo(truth(0), 5)
+
+    expect(vals[0]).toBeCloseTo(truth(clock.duration), 5) // went up first
+    expect(vals.at(-1)).toBeCloseTo(truth(0), 5)          // then down
+    expect(vals.at(-1)).toBeLessThan(vals[0])
+  })
+})
+
+describe('progress mode — signal behavior', () => {
+  it('does not emit for events that leave progress unchanged (flags)', () => {
+    // mnswpr: the flag at offset 200 must NOT produce a progress update.
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(envelope, s, { progress: createProgressReducer(board) })
+    const updates = []
+    clock.onProgress(u => updates.push(u))
+    clock.play()
+    s.advance(400)
+    // reveals at 0, 100, 300 changed progress; the flag at 200 did not.
+    expect(updates.map(u => u.position)).toEqual([0, 100, 300])
+    expect(updates.map(u => Math.round(u.progress))).toEqual([13, 25, 100])
+  })
+
+  it('emits nothing when no progress adapter is supplied', () => {
+    const clock = new PlaybackClock(envelope, fakeScheduler())
+    const updates = []
+    clock.onProgress(u => updates.push(u))
+    clock.seek(clock.duration)
+    expect(updates).toEqual([])
+    expect(clock.progress()).toBe(null)
+  })
+
+  it('unsubscribe stops progress delivery', () => {
+    const clock = new PlaybackClock(envelope, fakeScheduler(), { progress: dummyReduce })
+    const updates = []
+    const off = clock.onProgress(u => updates.push(u))
+    clock.seek(100)
+    off()
+    clock.seek(300)
+    expect(updates).toHaveLength(1) // only the first jump delivered
+  })
+})

packages/replay/test/schema-dispatch.test.js

@@ -0,0 +1,116 @@
+// @ts-check
+import { describe, it, expect } from 'vitest'
+import { PlaybackClock, readEnvelope } from '@cozy-games/replay'
+import { createMoveLog } from '@cozy-games/move-log'
+
+function fakeScheduler(start = 0) {
+  let now = start
+  let nextId = 1
+  const timers = new Map()
+  return {
+    clock: () => now,
+    setTimeout: (fn, ms) => {
+      const id = nextId++
+      timers.set(id, { at: now + Math.max(0, ms), fn })
+      return id
+    },
+    clearTimeout: (id) => { timers.delete(id) },
+    advance(ms) {
+      const target = now + ms
+      for (;;) {
+        let due = null
+        for (const [id, timer] of timers) {
+          if (timer.at <= target && (due === null || timer.at < due.at)) due = { id, ...timer }
+        }
+        if (!due) break
+        timers.delete(due.id)
+        now = due.at
+        due.fn()
+      }
+      now = target
+    }
+  }
+}
+
+// A canonical v1 envelope.
+const v1 = () => createMoveLog([
+  { seq: 1, t: 0, event: { type: 'reveal', r: 0, c: 0 } },
+  { seq: 2, t: 100, event: { type: 'flag', r: 1, c: 1 } },
+  { seq: 3, t: 250, event: { type: 'chord', r: 2, c: 2 } }
+])
+
+describe('schema_version dispatch — v1 (built-in)', () => {
+  it('replays a v1 envelope through the dispatch path (not a bypass)', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(v1(), s)
+    const seen = []
+    clock.on(r => seen.push(r.event.type))
+    clock.play()
+    s.advance(250)
+    expect(seen).toEqual(['reveal', 'flag', 'chord'])
+  })
+
+  it('readEnvelope returns the canonical records for v1', () => {
+    const records = readEnvelope(v1())
+    expect(records.map(r => r.seq)).toEqual([1, 2, 3])
+    expect(records[0].event.type).toBe('reveal')
+  })
+})
+
+describe('schema_version dispatch — unknown versions fail loudly', () => {
+  it('throws a specific error for a synthetic future version (99)', () => {
+    const future = { schema_version: 99, events: [{ seq: 1, t: 0, event: {} }] }
+    expect(() => new PlaybackClock(future, fakeScheduler())).toThrow(/unsupported envelope schema_version 99 \(supported: 1\)/)
+    expect(() => readEnvelope(future)).toThrow(RangeError)
+  })
+
+  it('throws for a missing schema_version', () => {
+    expect(() => readEnvelope({ events: [] })).toThrow(/unsupported envelope schema_version undefined/)
+  })
+
+  it('rejects a non-object envelope', () => {
+    // @ts-expect-error — deliberately wrong type
+    expect(() => readEnvelope(null)).toThrow(TypeError)
+  })
+})
+
+describe('schema_version dispatch — adding a version', () => {
+  // A toy v2 format defined ENTIRELY in the test: a different field layout that a
+  // normalizer maps back to canonical { seq, t, event }. Adding it is one entry.
+  const v2Envelope = {
+    schema_version: 2,
+    log: [
+      { n: 1, ts: 0, payload: { type: 'reveal', r: 0, c: 0 } },
+      { n: 2, ts: 120, payload: { type: 'flag', r: 1, c: 1 } }
+    ]
+  }
+  const readV2 = env => env.log.map(e => ({ seq: e.n, t: e.ts, event: e.payload }))
+
+  it('replays a v2 fixture via a supplied reader (same code path)', () => {
+    const s = fakeScheduler()
+    const clock = new PlaybackClock(v2Envelope, s, {}, { readers: { 2: readV2 } })
+    const seen = []
+    clock.on(r => seen.push(r.event.type))
+    clock.play()
+    s.advance(120)
+    expect(seen).toEqual(['reveal', 'flag'])
+  })
+
+  it('readEnvelope normalizes v2 to canonical records with an extra reader', () => {
+    const records = readEnvelope(v2Envelope, { 2: readV2 })
+    expect(records).toEqual([
+      { seq: 1, t: 0, event: { type: 'reveal', r: 0, c: 0 } },
+      { seq: 2, t: 120, event: { type: 'flag', r: 1, c: 1 } }
+    ])
+  })
+
+  it('still rejects v2 when no reader is registered', () => {
+    expect(() => readEnvelope(v2Envelope)).toThrow(/unsupported envelope schema_version 2 \(supported: 1\)/)
+  })
+
+  it('validates a reader that returns a malformed (non-canonical) log', () => {
+    // A buggy reader whose output breaks the monotonic-seq invariant is caught.
+    const badReader = () => [{ seq: 2, t: 0, event: {} }, { seq: 1, t: 1, event: {} }]
+    expect(() => readEnvelope({ schema_version: 3 }, { 3: badReader })).toThrow(RangeError)
+  })
+})

packages/utils/package.json

@@ -0,0 +1,22 @@
+{
+  "name": "@cozy-games/utils",
+  "version": "0.0.1",
+  "description": "Shared, dependency-free browser utilities for Cozy Games (storage, timer, logger, loading, date buckets)",
+  "author": "Ayo Ayco",
+  "private": true,
+  "type": "module",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/ayo-run/mnswpr"
+  },
+  "main": "index.js",
+  "exports": {
+    ".": {
+      "default": "./index.js"
+    },
+    "./*": {
+      "default": "./*"
+    }
+  },
+  "license": "BSD-2-Clause"
+}