In mid-1991, programmer John Carmack experimented with making a fast 3D game engine by restricting the gameplay and viewpoint to a single plane, producing Hovertank 3D and Catacomb 3-D as prototypes. Wolfenstein 3D was the second major release by id Software, after the Commander Keen series of episodes. The player traverses each of the game’s levels to find an elevator to the next level or kill a final boss, fighting Nazi soldiers, dogs, and other enemies with knives and a variety of guns. In Wolfenstein 3D, the player assumes the role of Allied spy William “B.J.” Blazkowicz during World War II as he escapes from the Nazi German prison Castle Wolfenstein and carries out a series of crucial missions against the Nazis. Originally released on for DOS, it was inspired by the 1981 Muse Software video game Castle Wolfenstein, and is the third installment in the Wolfenstein series. Wolfenstein 3D is a first-person shooter video game developed by id Software and published by Apogee Software and FormGen.