# 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