 Originally developed for DOS, "Castles" used CGA/EGA/VGA graphics and supporting AdLib MIDI sound, as well as a mouse interface.It was ported to the Atari ST in 1991 and to the Amiga in 1992, and a PC-98 localization was sold in Japan.In 1991 an expansion pack, "The Northern Campaign", was released for DOS and in 1992 for Amiga.