    # File lib/rubygame/sprite.rb, line 305
                            def collide_group(group, killa=false, killb=false, &block)
                                    sprites = {}
                                    self.each { |sprite|
                                            col = sprite.collide_group(group)
                                            sprites[sprite] = col if col.length > 0
                                    }

                                    if block_given?
                                            sprites.each_pair do |a, bs|
                                                    bs.each { |b| yield(a, b) }
                                            end
                                    else
                                            # killa and killb only work if no block is given
                                            if killa
                                                    sprites.each_key { |sprite| sprite.kill }
                                            end
                                            if killb
                                                    sprites.each_value do |array|
                                                            array.each { |sprite| sprite.kill }
                                                    end
                                            end
                                    end

                                    return sprites
                            end