Narrative from magazine advert - "Can you journey across the long-forgotten Abyss and outwit the evil monsters that lurk in the shadows awaiting the foolhardy and careless adventurer. There are many bridges and many monsters. Will you be the one to make the Abyss safe to cross again."
Abyss was originally developed for the Sinclair ZX Spectrum, and submitted speculatively to CCS who requested some changes before agreeing to publish it. The game was subsequently ported to the BBC Micro model B and Acorn systems, although not by the original designer. A Commodore 64 version was begun by the original designer, but never finished.
It was written in ZX Spectrum BASIC, with a small amount of Z80 machine code to provide a colourful display for players completing the game. The game centres on a 2 dimensional maze seen from above. Users move around the maze, and when they reach a node they are presented with a challenge chosen at random.
In the BBC Micro version, one of the challenges was to fool the cyber-minotaur, "Alexisis", into giving you the correct code for one of the final exits of the game. Once all the challenges are completed, the player enters an arena and plays a clone of "Tron's Deadly Discs". This refinement was not present in the original ZX Spectrum version.
Source: Wikipedia, "Abyss (video game)," available under the CC-BY-SA License.