BBC Computer 32K, Acorn DFS, BASIC
BeebEM + casual disregard for copyright of 25+ year old software = retro gaming joy.
Snapper, the version before Acornsoft had to change it to look slightly less like Pac-Man
Now if only I can work out how to make Arcadians playable. Using caps lock/ctrl for the left/right keys may have made sense on the BBC Micro's keyboard but hammering the caps lock key repeatedly whenever you want to move left isn't really practical.