public void keyReleased(KeyEvent ke) {
		Action action = actionOf(ke.getKeyCode());
		if (action == null) return;
		releaseKey(action);

		switch (action) {
		case MOVE_UP:
			if (vy < 0) { vy = 0; }
			break;
		case MOVE_DOWN:
			if (vy > 0) { vy = 0; }
			break;
		case MOVE_LEFT:
			if (vx < 0) { vx = 0; }
			break;
		case MOVE_RIGHT:
			if (vx > 0) { vx = 0; }
			break;
		}
	}