public void clip(){
		if (pos_x < 0) pos_x = 0;
		else if (pos_x > max_x) pos_x = max_x;

		//turn on if you want it to stay on screen
//		if (pos_y < 0) pos_y = 0;
//		else if (pos_y > max_y) pos_y = max_y;
	}