code: function Ball(scene) {
      this.x = scene.width() / 2;
      this.y = scene.height() / 2;
      this.vx = 1;// + Math.random()* 2;
      this.vy = 1;// + Math.random() * 2;
  
      this.move = function () {
          this.x += this.vx;
          this.y += this.vy;
          if (this.y < 0) {
              this.y = 0;
              this.vy = -this.vy;
          } else if (this.y > scene.height()) {
              this.y = scene.height();
              this.vy = -this.vy;
          }
      };
      this.setPosition = function (pos) {
          this.x = pos.x;
          this.y = pos.y;
      };
      this.isOut = function () {
          if (this.x < 0) {
              return 'left';
          }
          if (this.x > scene.width()) {
              return 'right';
          }
          return false;
      };
  }
docs: Represents a ball object on the scene