zig Tryit Editor

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
body {
    margin: 0;
}
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>
  var myGamePiece;
  var myUpBtn;
  var myDownBtn;
  var myLeftBtn;
  var myRightBtn;
  function startGame() {
    myGamePiece = new component(30, 30, "red", 10, 120);
    myUpBtn = new component(30, 30, "blue", 50, 10);
    myDownBtn = new component(30, 30, "blue", 50, 70);
    myLeftBtn = new component(30, 30, "blue", 20, 40);
    myRightBtn = new component(30, 30, "blue", 80, 40);
    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.interval = setInterval(updateGameArea, 20);
      window.addEventListener('mousedown', function (e) {
        myGameArea.x = e.pageX;
        myGameArea.y = e.pageY;
      })
      window.addEventListener('mouseup', function (e) {
        myGameArea.x = false;
        myGameArea.y = false;
      })
      window.addEventListener('touchstart', function (e) {
        myGameArea.x = e.pageX;
        myGameArea.y = e.pageY;
      })
      window.addEventListener('touchend', function (e) {
        myGameArea.x = false;
        myGameArea.y = false;
      })
    },
    clear: function () {
      this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
  }
  function component(width, height, color, x, y) {
    this.width = width;
    this.height = height;
    this.speedX = 0;
    this.speedY = 0;
    this.x = x;
    this.y = y;
    this.update = function () {
      ctx = myGameArea.context;
      ctx.fillStyle = color;
      ctx.fillRect(this.x, this.y, this.width, this.height);
    }
    this.clicked = function () {
      var myleft = this.x;
      var myright = this.x + (this.width);
      var mytop = this.y;
      var mybottom = this.y + (this.height);
      var clicked = true;
      if ((mybottom < myGameArea.y) || (mytop > myGameArea.y) || (myright < myGameArea.x) || (myleft > myGameArea.x)) {
        clicked = false;
      }
      return clicked;
    }
  }
  function updateGameArea() {
    myGameArea.clear();
    if (myGameArea.x && myGameArea.y) {
      if (myUpBtn.clicked()) {
        myGamePiece.y -= 1;
      }
      if (myDownBtn.clicked()) {
        myGamePiece.y += 1;
      }
      if (myLeftBtn.clicked()) {
        myGamePiece.x += -1;
      }
      if (myRightBtn.clicked()) {
        myGamePiece.x += 1;
      }
    }
    myUpBtn.update();
    myDownBtn.update();
    myLeftBtn.update();
    myRightBtn.update();
    myGamePiece.update();
  }
</script>
<p>Click on the blue "buttons" to make the red square move.</p>
</body>

</html>