Looking for something to do with your Sunday afternoon? MiniDOOM, a 2D platformer and "parody game" based on the original DOOM, might very well hit the spot. Completely free and a minuscule download at 11MB, there's really no reason not to try it.
Created by Calavera Studio -- comprised of brothers Juan Carlos and Felipe Porcel -- MiniDOOM is more of a lesson in games development than a full-blown independent release, going by the pair's website:
MiniDOOM is very short parody game based on the classic game DOOM 1. We created it as part of a game programming course we gave over here to show how to make a simple platformer on GameMaker Studio.
I'm not sure of the legal ramifications, but id Software is usually pretty good about this sort of thing. That said, I'd play it sooner rather than later, if you're keen.
MiniDOOM [Calavera Studio]