public void mouseDragged(MouseEvent e){
	    Point clickPoint = e.getPoint();
	    if(barrierFlag && clickPoint.x >= 0 && clickPoint.y >=0
	       && clickPoint.x <= screen_width && clickPoint.y <= screen_width) {
		if(e.getButton() == MouseEvent.BUTTON1 || e.getButton() == 0) {
		    GridBoard.this.setBarrierPosition(clickPoint.x,clickPoint.y,true);
		} else {
		    GridBoard.this.setBarrierPosition(clickPoint.x,clickPoint.y,false);
		}
	    }
	}