# 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