In the game, the player is to manage a production line. A number of buns sit on a conveyor belt and, by rhythmic tapping of two keys on the computer, the player would have to decorate them with icing, sugar and walnuts to produce a 'gudbun'. The more gudbuns the player produces, the more wages that player earns.
The game was originally released on mail order only, and seems to have been very unpopular. No computer magazines reviewed the game at the time. It was written by A. J. Turner, who appears to have written only this one game. The full instructions to the game have been lost.
Source: Wikipedia, "Bun_Fun," available under the CC-BY-SA License.