It’s long been a game development legend that the creators of Doom made their own version of Super Mario Bros. 3 for the PC ages ago. Today, we get to see what it looked like.

Like almost everyone working in video games in the 1990s, John Carmack and John Romero were big fans of Nintendo’s output. But the pair responsible for the classic first-person-shooter went further than most admirers and built a PC demo version of the 1988 adventure featuring the company’s mascot. Romero shared a clip of the demo today on social media. This is the technology that would go on to power id Software’s own platformer Commander Keen. So, yeah, this is a pretty cool piece of history.


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