The "Doom" concept was proposed in late 1992, after the release of "Wolfenstein 3D" and its sequel "Spear of Destiny". John Carmack was working on an improved 3D game engine from those games, and the team wanted to have their next game take advantage of his designs. Several ideas were proposed, including a new game in their "Commander Keen" series, but John proposed a game about using technology to fight demons inspired by the "Dungeons & Dragons" campaigns the team played. The initial months of development were spent building prototypes, while Hall created the "Doom Bible", a design document for his vision of the game and its story; after id released a grandiose press release touting features that the team had not yet begun working on, the "Doom Bible" was rejected in favor of a plotless game with no design document at all.