diff --git a/index.js b/index.js
index 4e4a34f..7ac6bb5 100644
--- a/index.js
+++ b/index.js
@@ -8,17 +8,21 @@ let engine = Engine.create({
   },
 });
 
+const width = window.innerWidth > 0 ? window.innerWidth : screen.width;
+const height = window.innerHeight > 0 ? window.innerHeight : screen.height;
+console.log('>>> width, height', width, height);
+
 // create runner
 let runner = Runner.create();
-let ground = Bodies.rectangle(400, 610, 810, 60, { isStatic: true });
+let ground = Bodies.rectangle(width / 2, height - 300, width / 2, 60, { isStatic: true });
 
 // create a renderer
 let render = Render.create({
   element: document.getElementById("canvas"),
   engine: engine,
   options: {
-    width: 1600,
-    height: 800,
+    width: width - 18,
+    height: height - 150,
   },
 });
 
@@ -52,7 +56,7 @@ function addShape() {
   // to be continued
   // let oneShape = Bodies.circle(80, 80, 80);
   let oneShape = Bodies.polygon(
-    Math.random() * 450 + 1,
+    Math.random() * width / 2 + 12,
     Math.random() * 450 + 1,
     Math.random() * 12 + 1,
     Math.random() * 150 + 100