Total conversion

A total conversion (TC) is a PWAD that replaces all or almost all of the resources of the original game's IWAD, often with the goal of not only changing the visuals and sounds but also gameplay mechanics. Thus the end result is usually substantially different than the original game and considered a distinctly new game.

The first total conversion of classic Doom was the Aliens TC developed by Justin Fisher in 1994. Other notable examples are Batman Doom, Hacx, and Action Doom.