Before Wolfenstein 3-D, before Doom, the future founders of id Software had a crazy idea: create a version of Nintendo's mega-hit Super Mario Bros. 3 for the PC platform, then see if the Japanese gaming giant would work with them to make it an official product. Nintendo declined, relegating the project to a historical footnote.

Until now. Id founder John Romero has uploaded an extensive video of the demo to Vimeo, so we can see exactly what it looked like.

This demo was possible because John Carmack, the programming whiz who'd later create the mind-blowing engines that ran id's first-person shooters, figured out how to create a side-scrolling platformer using the primitive PCs of the 1980s. In its day, the demo was an impressive technological achievement that did something that previously seemed impossible. This would become Carmack's signature in the years to come.

When Nintendo passed on the idea, everyone responsible for the demo quit their jobs and founded id. They quickly retooled the game into an original title called Commander Keen and released it on December 14, 1990.

Take it from someone who lived it: A Mario-style platform game on PC was a huge deal at the time, and we booted up Commander Keen as soon as we installed an EGA graphics card with its 16 glorious simultaneous colors.