[XP Script] Plane - Hidden Class

The Script
Code:
#==============================================================================

# ? SG::Plane

#------------------------------------------------------------------------------

# by Selwyn

#==============================================================================

module SG; end

class SG::Plane

  attr_reader :ox, :oy

  #--------------------------------------------------------------------------

  # ? initialize

  #--------------------------------------------------------------------------

  def initialize(viewport = nil)

    @sprite = Sprite.new(viewport)

    @max_width = 640

    @max_height = 480

    @bitmap = nil

    @ox = 0

    @oy = 0

  end

  #--------------------------------------------------------------------------

  # ? z, zoom_x, zoom_y, opacity, blend_type, color, tone

  #    z=, zoom_x=, zoom_y=, opacity=, blend_type=, color=, tone=

  #--------------------------------------------------------------------------

  def method_missing(symbol, *args)

    @sprite.method(symbol).call(*args)

  end

  #--------------------------------------------------------------------------

  # ? bitmap=

  #--------------------------------------------------------------------------

  def bitmap=(bitmap)

    @bitmap = bitmap

    refresh

  end

  #--------------------------------------------------------------------------

  # ? ox=

  #--------------------------------------------------------------------------

  def ox=(ox)

    w = @sprite.viewport != nil ? @sprite.viewport.rect.width : @max_width

    @ox = ox % w

    @sprite.ox = @ox

  end

  #--------------------------------------------------------------------------

  # ? oy=

  #--------------------------------------------------------------------------

  def oy=(oy)

    h = @sprite.viewport != nil ? @sprite.viewport.rect.height : 

@max_height

    @oy = oy % h

    @sprite.oy = @oy

  end

  #--------------------------------------------------------------------------

  # ? refresh

  #--------------------------------------------------------------------------

  def refresh

    return if @bitmap.nil?

    w = @sprite.viewport != nil ? @sprite.viewport.rect.width : @max_width

    h = @sprite.viewport != nil ? @sprite.viewport.rect.height : 

@max_height

    if @sprite.bitmap != nil

      @sprite.bitmap.dispose

    end

    @sprite.bitmap = Bitmap.new(w * 2, h * 2)

    max_x = w / @bitmap.width

    max_y = h / @bitmap.height

    for x in 0..max_x

      for y in 0..max_y

        @sprite.bitmap.blt(x * @bitmap.width, y * @bitmap.height,

         @bitmap, Rect.new(0, 0, @bitmap.width, @bitmap.height))

      end

    end

    for i in 1...4

      x = i % 2 * w

      y = i / 2 * h

      @sprite.bitmap.blt(x, y, @sprite.bitmap, Rect.new(0, 0, w, h))

    end

  end

end