<script>
'use strict';

document.documentElement.onclick = (e) => {
  window.top.postMessage({ x: e.clientX, y: e.clientY, screenX: e.screenX, screenY: e.screenY }, "*");
};

window.onload = () => {	
  window.top.postMessage({ ready: true }, "*");
}
</script>
<style>
body {
	margin: 0;
  background: green;
}
</style>
<body></body>
