MUD1

Roy Trubshaw wrote it on a computer at the University of Essex, and Richard Bartle took it over and completed it: a text-only, multiplayer dungeon. There were no pictures on screen, only room descriptions and the words of other players scrolling by. When the university connected to ARPANET in 1980, this game became "the first game you could log into from across a network." The single idea of other people sharing the same world — first implemented here — makes this the ancestor of the MMOs that would appear twenty years later.