public void update() {
if (left_driving_box_ != null) {
x_ =
left_driving_box_.x()
+ left_driving_box_.get_width() / 2
+ Settings.BOX_GAP
+ get_width() / 2;
y_ = left_driving_box_.y();
} else if (falling_) update_position();
if (height_driver_ != null) y_ = height_driver_.y();
check_off_screen();
}