Hall was upset with the reception to his designs and how little impact he was having as the lead designer; Romero has since claimed that Hall was also still uninterested in the "Doom" concept at all. Hall was also upset with how much he was having to fight with John Carmack in order to get what he saw as obvious gameplay improvements, such as flying enemies. He began to spend less time working in the office, and in response John Carmack proposed that he be fired from id. Romero initially resisted, as it would mean that Hall would not receive any proceeds, but in July he and the other founders of id fired Hall, who went to work for Apogee. Hall was replaced in September, ten weeks before "Doom" was released, by game designer Sandy Petersen, despite misgivings over his relatively high age of 37 compared to the other early-20s employees and his religious background. The team also added a third programmer, Dave Taylor. Petersen and Romero designed the rest of the levels for "Doom", with different aims: the team felt that Petersen's designs were more technically interesting and varied, while Romero's were more aesthetically interesting. Romero's level design process was to build a level or part of a level, starting at the beginning, then play through it and iterate on the design, so that by the time he was satisfied with the flow and playability of the level he had played it "a thousand times". The first level, made by Romero, was the last created, intended to show off the new elements of the engine. The ending screen of each level, like in "Wolfenstein 3D", displays a "par time" for the level, as set by Romero.