def in_screen?(object_x, object_y = nil)
    unless object_y
      object = object_x
      object_x = object.x
      object_y = object.y
    end
    return false if object_x <= @display_x - 4
    return false if object_x >= @display_x + Graphics.width / 32 + 3
    return false if object_y <= @display_y - 4
    return false if object_y >= @display_y + Graphics.height / 32 + 3
    return true
  end