function Square() {
  let a = Math.floor(Math.random() * 501);
  let b = Math.floor(Math.random() * 501);
  let d = Math.floor(Math.random() * 101);

  this.x = a;
  this.y = b;
  this.d = d;

  this.draw = function(c) {
    c.fillStyle = "red";
    c.fillRect(this.x, this.y, this.d, this.d);
  }
}