Futurewar (1977)

Futurewar is a first person shooter game on the PLATO network. Players walk around in a maze-like first person environment with a gun right in front of them. Monsters can be found in the maze which need to be shot, as well as other players. There are different types of hazardous terrain such as fire, water, and radioactive waste. Elevators allow players to change levels. The bottommost level is called Hell and features the devil himself as a monster.