One version is common, at least one other version is rare
 In 1997, author Edgar M. Vigdal released V1.7 into the public domain bearing a keyfile registered in his name. Presumably due to potential copyright infringements of Atari's coin-op, he and other public repositories (e.g. Aminet) were asked to remove the game for download from their websites.
 Game has a quit back to WB option.
Known releases: V1.6 (19-May-95), V1.7 (27-Apr-97)