function Boulder(x,y,width,height,img)
      {
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
        this.img = img;

        this.draw = function(){
          ctx.drawImage(this.img, this.x, this.y, this.width, this.height);
        }
      }

      var boulderArray = [];

      function createBoulders()
      {
        boulderArray.push(new Boulder(canvas.width/2, 50, 50,50,boulderImg),
                          new Boulder(canvas.width/2, 220, 50,50,boulderImg)
                          );
      }
      createBoulders();

      boulderArray.forEach(draw);