Audio games are games that rely mostly, or entirely, on audio as the user interface. They are popular with, and mostly created by, blind and visually impaired computer users and programmers.
Due to limitations of the form, most of these games are arcade style or first person shooter games. The two main reasons for this are that most audio games are developed for an extremely small market and thus are extremely low budget productions, and that the size and complexity of creating and using audio interfaces tends to limit the possible styles of play.
Current audio games available include Lone Wolf (a submarine game), Audio Quake (an audio mod for Quake), Shades of Doom (a first person shooter), Super Liam (an arcade style game), and many, many more.
Recently, Nintendo has developed a mainstream audio game for the GameBoy Advanced, Nintendo DS, and other platforms as part of its Bit Generations series (also known as Digitylish or Digilux) called Sound Voyager. Unfortunately, this game is (thus far) only available in Japan, and is difficult for blind people to play due to the tree based menu structure.