Gameplay video from John Carmack's Super Mario Bros. 3 PC tech demo has been released. id Software presented the demo to Nintendo in 1990 to show them what could be done on a PC, Nintendo said thanks anyway. It later would become the engine for id Software's Commander Keen.
Pat the NES Punk discussed the Super Mario Bros. 3 PC demo on the CUPodcast:
Here is raw footage of the demo:
I think for its time the PC demo looks really good. Pat and Ian claim it was the first PC game to introduce side scrolling. Which made me think.. hmm.. it's amazing what the PC (the supposed "Standard Bearer" in the computer industry) couldn't do in 1990 when compared to the Amiga which was like a whole new world, and five years old by that time.