    # File lib/rubygame/sprite.rb, line 459
                            def <<(sprite)
                                    if not include? sprite
                                            super(sprite)
                                            while length > @limit
                                                    self.slice!(0)
                                            end
                                    else # move sprite to the back of the queue
                                            self.delete(sprite)
                                            super(sprite)
                                    end
                            end