class Rock {
  PImage img;
  int x, y;
  Rock(int px,int py){
      x = px;
      y = py;
      img = loadImage("20x20Rock.png");
      walls.add(new Wall(x,y));
   } 
     void draw(){
      image(img, (x * SQUARESIZE),(y * SQUARESIZE));
      
   }

}