Nethack is a single-player dungeon exploration game. The emphasis is
on discovering the detail of the dungeon. Each game presents a
different landscape - the random number generator provides an
essentially unlimited number of variations of the dungeon and its 
denizens to be discovered by the player in one of a number of
characters: you can pick your race, your role, and your gender.

User accounts that play this need to be members of the "games" group.