Left 4 Dead, we now have an idea of what the zombie apocalypse simulator would have been like had it released in the '80s. Valve is apparently aware of the project and finds the concept "hilarious." Ruth reveals that he plans to release the full game as a free download in early January 2010 for PC. It features all the campaigns from the original game, including 8-bit incarnations of the special infected, for two players to play through -- it is a NES game after all, fancy four-player wasn't standard.
Check out a video of the game after the break. The only thing we'd wish this "de-make" had was a sprite flickering zombie rush, so all the youngins could experience the glory of NES flicker when there were too many things on the screen at once for the system's 2KB of RAM.
Update 2: Check out Eric Ruth's interview with sister site Big Download
Update: Changed "didn't exist" to "wasn't standard." Nintendo released the NES Four Score adapter in 1990. Remember the one for the original Game Boy?