def point_towards(target)
      if target == :mouse
        tx = Input.mouse_pos_x
        ty = Input.mouse_pos_y
      else
        tx = target.x
        ty = target.y
      end
      dx = tx - x
      dy = ty - y
      self.angle = Math.atan2(dy, dx) * 180 / Math::PI
    end
def point_towards(target)
      if target == :mouse
        tx = Input.mouse_pos_x
        ty = Input.mouse_pos_y
      else
        tx = target.x
        ty = target.y
      end
      dx = tx - x
      dy = ty - y
      self.angle = Math.atan2(dy, dx) * 180 / Math::PI
    end
(  )に向ける