MUA, multi-user adventure, was the term preferred by Richard Bartle. He considered MUD to refer to MUD1 and thus ambiguous. However MUA never came into general use, and MUD became the umbrella term used to refer to all multi-player adventure games, although generally only text-based games. Another term in use in the United Kingdom was MUG, multi-user game, but that term, not used among gamers, fell out of use.