Commodore PET Version
The game first appeared around 1981 as BASIC listing for the Commodore PET in the British Computing Today
magazine. The magazine's publisher Argus Press released home computer versions shortly after, and there also were some unofficial versions, so that the game was available on an unusually wide array of platforms: There were several versions for the ZX Spectrum and C-64 (including a Norwegian version called Dalen
for the latter!), as well as versions fot PET, TRS-80, BBC Model B, Oric-1 and Sharp MZ80K.
The 2001 DOS remake by Paul Robson came in two versions, one with Borland BGI graphics, another one with GNU C and Allegro.