Всемогущий,
<!DOCTYPE HTML>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body style="border:0px;padding:0px;margin:0px;overflow:hidden;" >
<canvas id='canvas' height='0' width='0' style="border:0px;padding:0px;margin:0px;overflow:hidden;" ></canvas>
<script>
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
function draw() {
ctx.fillRect((canvas.width - 100) / 2, (canvas.height - 100) / 2, 100, 100)
}
function game() {
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
draw();
requestAnimationFrame(game)
}
requestAnimationFrame(game);
</script>
</body>