Nintendo is finally allowing its intellectual properties on third-party hardware, a couple of decades after Doom Developer Id Software pitched a port of Super Mario Bros. 3 for PC. That port even had a demo.

A long time ago, back around the late '80s and early Nintendo, console was king in the realm of video games and PC was not.

id Software, known as Ideas from the Deep or IFD back then, figured out a way to smooth out the screen tearing that made side-scrolling games run horribly on PC.

Nintendo turned down the PC version of popular platforming game, opting to preserve the value of its hardware by keeping its software exclusive. However, that side-scrolling technology would later be used to develop Commander Keen, a relatively successful platforming game for the PC.

To celebrate Commander Keen's quarter-century milestone, id Software cofounder John Romero shared a video of the company's old Super Mario Bros. 3 demo for PC.

"Happy 25th Birthday, Commander Keen! In honor I'm sharing a video of our SMB3 demo we made for Nintendo on 9/28/1990," Romero tweeted.

The Super Mario Bros. 3 demo was born of a tech demo for Nintendo while Romero and other id Software founders were at Softdisk. The demo used technology the group didn't believe Softdisk cared about or would ever use, so John Carmack talked it over with Romero and Tom Hall.

"We decided to create a real, polished Super Mario 3 demo and send it to Nintendo Of America to see if we could do the PC port of the game," Carmack recalled. "The SM3 demo made it to Nintendo of Japan and Shigeru Miyamoto specifically. They were very impressed with the demo but their corporate plan was to never release their IP on a platform other than their own."

While the bunch was trying to convince Nintendo about the PC port, Apogee Software's Scott Miller was working to recruit Carmack to create some shareware games, and that's where Commander Keen got him his big break.

So back to the Super Mario Bros. 3 demo. Check it out the video below.