MUDs combine elements of role-playing games, hack and slash, player versus player, interactive fiction, and online chat.Players can read or view descriptions of rooms, objects, other players, non-player characters, and actions performed in the virtual world.When one of the two programmers left Compu Net, the remaining programmer, Alan Lenton, decided to rewrite the game from scratch and named it Federation II (at the time no Federation I existed). Federation II was later picked up by AOL, where it became known simply as "Federation: Adult Space Fantasy".Federation later left AOL to run on its own after AOL began offering unlimited service.Starting out as a hobby, SHADES became accessible in the UK as a commercial MUD via British Telecom's Prestel and Micronet networks.
Klietz wrote a game called Milieu using Multi-Pascal on a CDC Cyber 6600 series mainframe which was operated by the Minnesota Educational Computing Consortium.
Numerous games are listed at various web portals, such as The Mud Connector.
The history of modern massively multiplayer online role-playing games (MMORPGs) like Ever Quest and Ultima Online, and related virtual world genres such as the social virtual worlds exemplified by Second Life, can be traced directly back to the MUD genre.
Players typically interact with each other and the world by typing commands that resemble a natural language.
Traditional MUDs implement a role-playing video game set in a fantasy world populated by fictional races and monsters, with players choosing classes in order to gain specific skills or powers.