List of ZZT world versions (the first small-endian 16-bit number in the world file): -1 ZZT -2 Super ZZT -4 FreeZZT -5 Nautilus -2777 (.ZXT or .ZAX file, for extensions of Super ZZT) -3545 (.ZXT or .ZAX file, for extensions of ZZT) -7641 (World file requiring ZXT/ZAX for parsing) An external list with the same information can be found at: https://zeta.asie.pl/wiki/doku.php?id=registry:world_format_ids