jugando con p5.js by aaizemberg

index.html

<!doctype html>
<html>
  <head>
    <script src="//cdnjs.cloudflare.com/ajax/libs/p5.js/0.2.2/p5.min.js"></script>
  </head>
<body>

<script>
  function setup() {
    createCanvas(960, 500);
  }

  function draw() {
    ellipse(mouseX,mouseY, width-mouseX,height-mouseY);
  }
</script>

</body>
</html>