public void clear() {
        for (DestructibleBrick _dBrick : _dBricks) {
            Buffer.deleteElement(_dBrick);
        }
        _dBricks.clear();
        for (IndestructibleBrick _iBrick : _iBricks) {
            Buffer.deleteElement(_iBrick);
        }
        _iBricks.clear();
        for (Ball _ball : _balls) {
            Buffer.deleteElement(_ball);
        }
        _balls.clear();
        Buffer.deleteElement(_racket);
        _racket = null;
    }