Marathon is a First-Person Shooter (FPS) that was originally released for the Apple Macintosh in 1994 and was subsequently ported to several other platforms. Set in 2794 A.D., players in the game become a Security Officer on the UESC starship Marathon, orbiting Tau Ceti IV. Tasked with defending the ship and colony from alien slavers, the Pfhor, players navigate complex interactions between three AIs, uncovering deeper mysteries aboard the Marathon.