There's something a bit magical about shareware stalwart Doom and folks' compulsion to make it run on absolutely everything. Present a sufficiently motivated individual with the game's open source code, and a less than powerful bit of kit offering maybe the barest whisper of a GUI, and you can be sure they'll put two and two together.
So, when I ask 'what does a pregnancy test, gut bacteria, and 100 pounds of moldy potatoes all have in common?', you know the answer. Well, now we can add QR codes to that list—with an asterisk. Developer Kuber Mehta has created something exceedingly light-weight that can be compressed, encoded into, and then extracted from a single QR code (via TechSpot).
However, as the developer chronicles in a recent blog post, it turns out getting Doom itself to run via QR code is actually not that straightforward. Just for a start, QR codes can only encode up to 3 KB of data, and as Mehta points out, the original Doom's chaingun sprite alone is an absolutely whopping 1.2 KB.
So, the developer decided upon a compromise, writing that his eventual 'absurd premise' became "Create a playable DOOM-inspired game smaller than three paragraphs of plain text."
So, it's not actually Doom—that's the asterisk—but Mehta's game is definitely Doom-like. Taking heavy inspiration not just from the original 1993 shooter, but liminal space creepypasta The Backrooms as well, Mehta's project is called 'the backdooms.' It's very silly as names go, but I'm still kicking myself for not having come up with it.
Crafted in HTML, Mehta had to make every character of his code count, and he was able to compress variables to single letters by using what he describes as "EXTREMELY aggressive minification". Looking at the resulting code kind of makes me feel like a Doom demon taking a headshot, but I'm nonetheless impressed. Unfortunately, encoding HTML into a QR code is also not a walk in the park, with the usual go-to Base64 conversion route leaving very little of an already meagre storage budget for the game itself.
So, Mehta turned to the cursed trinity of ChatGPT, DeepSeek, and Claude to source a solution.
Demonstrating why AI chatbots are not especially useful referencing tools, Mehta writes, "I talked to [the three AI chatbots] for two days, whenever I could [...] 100 different prompts to each one to try to do something about this situation (and being told every single time hosting it on a website is easier!?) Then, ChatGPT casually threw in DecompressionStream [a WebAPI component built into most browsers]."
This was not the last hurdle for the project to creatively hurl itself over. Though the backdooms originally used tiny baked-in maps, Mehta instead chose to implement maps based on a seed that infinitely generates.
While somewhat random, this means maps can be retrieved if you've got the seed number it was generated from—however, the real magic trick was then making this look like even rudimentary 3D. Borrowing a page out of Doom's original playbook, Mehta deployed a simplified version of raycasting—so, technically, this (and the original Doom) is a 2D game in a trench coat.
As a result of all of the above constraints, 'the backdooms' is a visually limited project, seeing you avoiding red-eyed rectangles amid grey walls, but it definitely gets the point across. You can take a deeper dive into the guts of the project yourself via GitHub.
Naturally, compressing everything into a QR code isn't going to be practical for most projects, but it's definitely in the shareware spirit of the original Doom. Thrifty use of underpowered resources is always impressive—especially when a powerful quantum computer struggles to run even a wireframe version of Doom.
Along the lines of getting the most out of incredibly limited foundations, you may also be interested in Roche Limit, a horror game made entirely in PowerPoint. Despite the jaunty trailer, that's a project with a powerfully cursed (though no less compelling) vibe. Speaking of tales of terror, maybe I should dust off that draft about a post-apocalyptic world inherited by cockroaches with Doom's source code encoded in their DNA…
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