public void target(Char ch) {
   if (ch != null && ch.isAlive()) {
     target = ch;
   } else {
     target = null;
   }
 }
  @Override
  public void update() {
    super.update();

    if (target != null && target.isAlive() && target.sprite.visible) {
      CharSprite sprite = target.sprite;
      bg.scale.x = sprite.width;
      level.scale.x = sprite.width * target.HP / target.HT;
      bg.x = level.x = sprite.x;
      bg.y = level.y = sprite.y - HEIGHT - 1;

      visible = true;
    } else {
      visible = false;
    }
  }