zig Tryit Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>
  var myGamePiece;
  function startGame() {
    myGamePiece = new component(30, 30, "red", 225, 225);
    myGameArea.start();
  }
  var myGameArea = {
    canvas: document.createElement("canvas"),
    start: function () {
      this.canvas.width = 480;
      this.canvas.height = 270;
      this.context = this.canvas.getContext("2d");
      document.body.insertBefore(this.canvas, document.body.childNodes[0]);
      this.frameNo = 0;
      this.interval = setInterval(updateGameArea, 20);
      window.addEventListener('keydown', function (e) {
        e.preventDefault();
        myGameArea.keys = (myGameArea.keys || []);
        myGameArea.keys[e.keyCode] = (e.type == "keydown");
      })
      window.addEventListener('keyup', function (e) {
        myGameArea.keys[e.keyCode] = (e.type == "keydown");
      })
    },
    stop: function () {
      clearInterval(this.interval);
    },
    clear: function () {
      this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
  }
  function component(width, height, color, x, y, type) {
    this.type = type;
    this.width = width;
    this.height = height;
    this.speed = 0;
    this.angle = 0;
    this.moveAngle = 0;
    this.x = x;
    this.y = y;
    this.update = function () {
      ctx = myGameArea.context;
      ctx.save();
      ctx.translate(this.x, this.y);
      ctx.rotate(this.angle);
      ctx.fillStyle = color;
      ctx.fillRect(this.width / -2, this.height / -2, this.width, this.height);
      ctx.restore();
    }
    this.newPos = function () {
      this.angle += this.moveAngle * Math.PI / 180;
      this.x += this.speed * Math.sin(this.angle);
      this.y -= this.speed * Math.cos(this.angle);
    }
  }
  function updateGameArea() {
    myGameArea.clear();
    myGamePiece.moveAngle = 0;
    myGamePiece.speed = 0;
    if (myGameArea.keys && myGameArea.keys[37]) { myGamePiece.moveAngle = -1; }
    if (myGameArea.keys && myGameArea.keys[39]) { myGamePiece.moveAngle = 1; }
    if (myGameArea.keys && myGameArea.keys[38]) { myGamePiece.speed = 1; }
    if (myGameArea.keys && myGameArea.keys[40]) { myGamePiece.speed = -1; }
    myGamePiece.newPos();
    myGamePiece.update();
  }
</script>
<p>Make sure the gamearea has focus, and use the arrow keys to move the red square around.</p>
</body>

</html>