and start their own company. When their boss, Softdisk owner Al Vekovius, confronted them on both their plans and their use of company resources to develop the game—the team had created it on their work computers, both in the office after hours and by taking the computers to John Carmack's house on the weekends—the team made no secret of their intentions. After a few weeks of negotiation, the team agreed to produce a series of games for Gamer's Edge, one every two months. Ideas from the Deep, now formally established as id Software, used some of these to prototype ideas for their own games. Adrian Carmack used them to push his preferred, dark art style, while John Carmack began to experiment with 3D computer graphics, which until then was largely the purview of flight simulation games such as Wing Commander (1990). Carmack found that this was largely due to the limitations of personal computers of the time, which had difficulty displaying a fast action game in 3D due to the number of surfaces it needed to calculate, but felt that the increasing computational power of PCs meant that it may be possible. During 1991, he experimented with limiting the possible surfaces the computer needed to display, creating game levels with walls designed only on a flat grid rather than with arbitrary shapes or angles. He also took the unusual approach of creating the displayed graphics through ray casting, in which only the surfaces visible to the player were calculated rather than the entire area surrounding the player. After six weeks of development, Carmack had created a rudimentary 3D game engine that used animated 2D sprites for enemies. Id Software then used the engine for the April 1991 Softdisk game Hovertank 3D, in which the player drives a tank through a plane of colored walls and shoots nuclear monsters. In the fall of 1991, after the team—sans Wilbur—had relocated to Madison, Wisconsin, and he had largely finished the engine work for Commander Keen in Goodbye, Galaxy, Carmack decided to implement a feature from Ultima Underworld: The Stygian Abyss, a role-playing game in development by Blue Sky Productions. Ultima Underworld was planned to display texture-mapped 3D graphics without Hovertanks restrictions of flat walls and simple lighting. Deciding that he could add texture mapping without sacrificing the engine's speed or greatly increasing the system requirements as Underworld was doing, Carmack enhanced the engine