Human ingenuity is a powerful—sometimes terrifying—thing. Throughout history, no matter how basic the tools available to us, we have always found a way to build the weird obsessions that appear in our minds. You know, like Stonehenge, or the Pyramids, or Doom (1993).

No, really. In a recent chat with Jesse Petrilla on YouTube, id co-founder and Doom lead artist Adrian Carmack revealed that, when it came time to put together the classic FPS' animations, the incredibly complex and advanced animation tool he used to do it was… the undo key.

"As an artist, oftentimes you end up making your own tools," said Carmack. "You know, there was no animation tool, so I started using the undo key to create animation—the undo key in Deluxe Paint, so I'd go back and forth."

If you're unclear as to how that works, remember that animations in original Doom weren't really animations as we think of them today, with models seamlessly transitioning through countless subtle movements to create smooth motion. Doom sprites, from your enemies to your weapons, were all very frame-y indeed. Working with relatively few frames meant Carmack could create and capture animation loops by cycling through frames in Deluxe Paint using undo/redo.

Carmack's fellow id devs were duly astounded by his innovation. "The guys were pretty impressed that I came up with that for animation," he says. "But that's the tool I used, and [Doom programmer] John Carmack really limited me on the frames of animation, so I was always trying to be very frugal… to make this animation look as good as I can with as few frames as possible."

Carmack suggests this was not a risk-free process. Constantly undoing things means you might inadvertently delete your own work, but it sounds like Carmack quickly worked out a system that minimised that possibility. "The first time you lose some work, you're pretty cautious after that. And so, it was very unusual for me to lose anything, doing it that way."

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One of Josh's first memories is of playing Quake 2 on the family computer when he was much too young to be doing that, and he's been irreparably game-brained ever since. His writing has been featured in Vice, Fanbyte, and the Financial Times. He'll play pretty much anything, and has written far too much on everything from visual novels to Assassin's Creed. His most profound loves are for CRPGs, immersive sims, and any game whose ambition outstrips its budget. He thinks you're all far too mean about Deus Ex: Invisible War.