for the first six months, the programmer Tim Cain was the sole developer. Cain eventually enlisted the aid of Interplay employees during their spare time. The development team behind Fallout—led by Cain, the designer Christopher Taylor, and the art director Leonard Boyarsky—reached 15 people in 1995. In 1996, the producer Feargus Urquhart recruited some Interplay workers to join the team, expanding it to 30. Cain considered the team "amazing" for their dedication, while Urquhart described working under Interplay as "barely controlled chaos". The tentative title, Vault-13: A GURPS Post-Nuclear Role-Playing Game, was rejected as unfitting. Armageddon was considered as an alternative, but was already in use for another Interplay project (which was later canceled). Interplay's president Brian Fargo suggested the title Fallout . Interplay intended to use "I Don't Want to Set the World on Fire" by the Ink Spots as the theme song, but was hindered by a copyright problem, so another Ink Spots song, "Maybe", was used. The development concluded on October 1, 1997, after three and a half years and a total cost of approximately $3million. Engine and design Fallout started as a game engine—a framework for a video game—that Cain was developing during his spare time, based on the tabletop role-playing game Generic Universal RolePlaying System (GURPS). It entered more coordinated development after Cain convinced Fargo of its potential, and Interplay announced it had acquired the GURPS license in 1994. The first Fallout prototype was finished that year. The team considered making the game first-person and 3D, but discarded the idea because the models would not have held the desired amount of detail. They instead selected an oblique projection, producing a trimetric perspective. Designed to be open-world and non-linear, Fallout was balanced so that, even though side quests are optional, characters who do not improve their skills and experience through them would be too ill-equipped to finish. However, Taylor also added the 150-day time limit to the game to keep the player focused on the main quests. The game was nearly canceled in late 1994 after Interplay acquired the licenses to the Dungeons & Dragons franchises Forgotten Realms and Planescape, but Cain convinced Interplay to let him finish. After the success of the role-playing video game Diablo, released in January 1997, Cain resisted pressure to convert Fallout into a real-time multiplayer game. In March 1997, Interplay dropped the license for GURPS due to creative differences with