for the company's next game, just as he had experimented with creating a 3D game engine prior to the development of Wolfenstein 3D. Between May and Spear of Destinys release in September 1992, he created several experimental engines, including one for a racing game, before working on an enhanced version of the Wolfenstein engine to be licensed to Raven Software for their game ShadowCaster. For this engine, he developed several enhancements to the Wolfenstein engine, including sloped floors, textures on the floors and ceilings in addition to the walls, and fading visibility over a distance. The resulting engine was much slower than the Wolfenstein one, but was deemed acceptable for an adventure game like ShadowCaster. Following the release of Spear of Destiny and the completion of the ShadowCaster engine, id Software discussed what their next title would be. They wanted to create another 3D game using Carmack's new engine as a starting point, but were largely tired of Wolfenstein. Lead designer Tom Hall was especially weary of it, and pushed for the team to make another game in the Commander Keen series; the team had created seven episodes in the series in 1990–91 as their first games, but the planned third set of episodes had been dropped in favor of Wolfenstein 3D. While Carmack was initially interested in the idea, the rest of the team was not. They collectively felt that the platforming gameplay of the series was a poor fit for Carmack's fast-paced 3D engines, and especially after the success of Wolfenstein were interested in pursuing more games of that type. Additionally, the other two co-founders of id were not interested in creating another Keen game: John Romero, the designer of Wolfenstein, was not interested in doing another "cutesy" game, and lead artist Adrian Carmack preferred to create art in a darker style than the Keen games. John Carmack soon lost interest in Keen idea as well, instead coming up with his own concept: a game about using technology to fight demons, inspired by the Dungeons & Dragons campaigns the team played, combining the styles of Evil Dead II and Aliens. The concept originally had a working title of "Green and Pissed", which was also the name of a concept Hall had proposed prior to Wolfenstein, but Carmack soon named the proposed game after a line in the film The Color of Money: "'What's in the case?' / 'In