In the far future, gladiator-style blood sports were revived. The hero of the game gets informed of them through an associate, whom he believes to be dead. In order to get to the bottom of the mystery, he has to become a player in those cruel battles, where only the most ruthless survive. Everyone fights to death, because the loser's fate is worse than just death - the meat of defeated contestants is used in fast-food burgers...
XS is a first-person shooter that consists entirely of these gladiatorial arena battles, in a certain way simulating deathmatch competitions in a single-player frame. The player has to fight through a number of rounds of free-for-all combat, being able to choose two weapons before a match begins. Otherwise, the game follows standard FPS rules, with strafing, jumping, occasional platform-hopping, etc.