diff --git a/app-cart/src/Cart.jsx b/app-cart/src/Cart.jsx
index 3951afb..c1610ae 100644
--- a/app-cart/src/Cart.jsx
+++ b/app-cart/src/Cart.jsx
@@ -1,71 +1,102 @@
 // @ts-check
-// import { broadcast } from 'utils/orchestrator'
-import React, { useState } from "react";
-const Cart = () => {
-  const [products, setProducts] = useState([
-    {
-      name: "Shoe A",
-      description: "It is a good shoe",
-      price: 100,
-      count: 2,
-    },
-    {
-      name: "Shoe B",
-      description: "It is a comfortable shoe",
-      price: 120,
-      count: 7,
-    },
-  ]);
+import { broadcast, listen } from "utils";
+import React, { Component } from "react";
 
-  // listen to add-to-cart messages
-  // if item is already in cart, increment count
+class Cart extends Component {
+  constructor(props) {
+    super(props);
+    this.state = {
+      products: [
+        {
+          name: "Shoe A",
+          description: "It is a good shoe",
+          price: 100,
+          count: 2,
+        },
+        {
+          name: "Shoe B",
+          description: "It is a comfortable shoe",
+          price: 120,
+          count: 7,
+        },
+      ],
+    };
+  }
 
-  const getTotal = () => {
+  getTotalItems = () => {
+    const { products } = this.state;
+    return products.reduce((acc, product) => {
+      return acc + product.count;
+    }, 0);
+  };
+
+  getTotalPrice = () => {
+    const { products } = this.state;
     return products.reduce((acc, product) => {
       return acc + product.price * product.count;
     }, 0);
   };
 
-  const decreaseCount = (index) => {
-    // if in cart, decrease count
-    const updatedProducts = [...products];
-    if (updatedProducts[index].count > 1) {
-      updatedProducts[index].count--;
+  addProduct = (product) => {
+    const { products } = this.state;
+    const index = products.findIndex((p) => p.name === product.name);
+    if (index > -1) {
+      const updatedProducts = [...products];
+      updatedProducts[index].count++;
+      this.setState({ products: updatedProducts });
     } else {
-      updatedProducts.splice(index, 1);
+      this.setState({ products: [...products, { ...product, count: 1 }] });
     }
-    setProducts(updatedProducts);
   };
 
-  const increaseCount = (index) => {
-    // if in cart, increase count
-    const updatedProducts = [...products];
-    updatedProducts[index].count++;
-    setProducts(updatedProducts);
+  removeProduct = (product) => {
+    const { products } = this.state;
+    const index = products.findIndex((p) => p.name === product.name);
+    if (index > -1) {
+      const updatedProducts = [...products];
+      updatedProducts[index].count--;
+      this.setState({ products: updatedProducts });
+    }
   };
 
-  return (
-    <div>
-      <h2>🛒 Cart</h2>
-      <ul>
-        {products.map((product, index) => (
-          <li key={index}>
-            <span>({product.count}x) </span>
-            <span>{product.name}</span>
-            <span> - </span>
-            <strong>${product.price * product.count}</strong>
-            <span>
-              <button onClick={() => decreaseCount(index)}> - </button>
-              <button onClick={() => increaseCount(index)}> + </button>
-            </span>
-          </li>
-        ))}
-      </ul>
+  componentDidMount() {
+    broadcast("update-count", this.getTotalItems());
+    listen("add-product", this.addProduct);
+  }
 
-      <span>Total: </span>
-      <strong>${getTotal()}</strong>
-    </div>
-  );
-};
+  componentDidUpdate(prevProps, prevState) {
+    const { products } = this.state;
+    if (prevState.products !== products) {
+      broadcast("update-count", this.getTotalItems());
+    }
+  }
+
+  render() {
+    const { products } = this.state;
+
+    return (
+      <div>
+        <h2>🛒 Cart</h2>
+        <ul>
+          {products.map((product, index) => (
+            <li key={index}>
+              <span>({product.count}x) </span>
+              <span>{product.name}</span>
+              <span> - </span>
+              <strong>${product.price * product.count}</strong>
+              <span>
+                <button onClick={() => this.removeProduct(product)}> - </button>
+                <button onClick={() => this.addProduct(product)}> + </button>
+              </span>
+            </li>
+          ))}
+        </ul>
+
+        <span>Total: </span>
+        <strong>${this.getTotalPrice()}</strong>
+      </div>
+    );
+  }
+}
 
 export default Cart;
diff --git a/app-heading/src/App.jsx b/app-heading/src/App.jsx
index d5922d8..e0d34c3 100644
--- a/app-heading/src/App.jsx
+++ b/app-heading/src/App.jsx
@@ -1,4 +1,5 @@
-import React from "react";
+import { listen } from "utils";
+import React, { useEffect } from "react";
 import "./App.css";
 
 const App = (props) => {
@@ -6,6 +7,11 @@ const App = (props) => {
   const [count, setCount] = React.useState(0);
 
   // listen to add-to-cart messages
+  useEffect(() =>
+    listen("update-count", (count) => {
+      setCount(count);
+    })
+  );
 
   return (
     <section className="app-b">
diff --git a/app-products/src/App.jsx b/app-products/src/App.jsx
index 6ae3222..7d4a067 100644
--- a/app-products/src/App.jsx
+++ b/app-products/src/App.jsx
@@ -1,3 +1,4 @@
+import { broadcast } from "utils";
 import styles from "./App.module.css";
 
 function App() {
@@ -25,8 +26,8 @@ function App() {
   ];
 
   const addToCart = (product) => {
-    console.log(">>> add to cart", product);
     // broadcast add product to cart
+    broadcast("add-product", product);
   };
 
   return (
diff --git a/utils/index.js b/utils/index.js
index e69de29..f3fb4e4 100644
--- a/utils/index.js
+++ b/utils/index.js
@@ -0,0 +1 @@
+export { broadcast, listen } from "./orchestrator.mjs";
diff --git a/utils/orchestrator.mjs b/utils/orchestrator.mjs
index 2c27412..7856c19 100644
--- a/utils/orchestrator.mjs
+++ b/utils/orchestrator.mjs
@@ -1,3 +1,19 @@
 // implement messaging system between MF's
+const listeners = {};
+
 // - broadcast message
-// - listen to message & attach callback
\ No newline at end of file
+export function broadcast(action, data) {
+  window.parent.postMessage({ action, data });
+  console.log("broadcast", { action, data });
+}
+
+// - listen to message & attach callback
+export function listen(action, callback) {
+  window.parent.addEventListener("message", (event) => {
+    const { data } = event;
+
+    if (data.action === action) {
+      callback(data.data);
+    }
+  });
+}