Wolfenstein was completed, but the team moved on to Doom (1993) instead. Id did not return to the series afterwards, instead continuing to focus on 3D first-person shooters. In October 1999 during an online question and answer session, John Carmack, while discussing that the original founders of id Software were unlikely to ever work together on a game again, mentioned that he was considering the idea of making a Commander Keen game for the Game Boy Color handheld game console. Activision formally announced at the start of May 2001 that a new Commander Keen game had been developed by David A. Palmer Productions, and would be released at the end of the month. An interview the following week with founder David A. Palmer explained that the original idea for the game came from id, who approached Activision to produce it; Activision in turn recommended Palmer as the developer for the project as they had been attempting to get an agreement with id and Activision for several years for his studio to make a Game Boy Color version of several of their games. While Palmer was the developer for the game, id collaborated with the studio, with id having approval over game design elements and artist Adrian Carmack making some tile artwork for the game. Reception Commander Keen in Invasion of the Vorticons was an immediate hit for Apogee: the company's previous sales levels had been around US$7,000 per month, but by Christmas Keen already had sales of almost US$30,000. Miller described the game as "a little atom bomb" to magazine editors and BBS controllers when asked about it, and recruited his mother and hired his first employee to handle sales and phone calls from interested players. By June 1991, the game was bringing in over US$60,000 per month. Chris Parker of PC Magazine later in 1991 referred to the game's release as a "tremendous success". In 2009, Miller estimated the game's lifetime sales as between 50,000 and 60,000 units. A contemporary review by Barry Simon of PC Magazine praised the game's graphical capabilities as having a "Nintendo feel", though he termed the graphics as "well drawn" but "not spectacular" in terms of resolution. He noted that the game was very much an arcade game that players would not purchase for "its scintillating plot or ground-breaking originality", but said that all three episodes were very fun to play and that the