Doom can run on so many weird devices now, it’s easier to tally up the things that don’t support id’s 1993 masterpiece. But running a game inside another game always tickles my lizard brain, and Squaresweets on GitHub has delivered: The Ultimate Doom, fully playable within the New Blood FPS Ultrakill.
Every level in Ultrakill begins with a diegetic shop terminal, sort of like the ones in Prey or the new (oh god, the newest one is 10 years old now) Deus Exes: You can walk up and seamlessly use your mouse to select loadouts without the game pausing, locking you in place, or hijacking the screen for a disconnected UI window. It’s a neat effect I’m always happy to see, and now protagonist bot V1 can use it to get some frags in before it gets some frags in.
Squaresweets built off the work of xabblll’s DoomInUnityInspector and sinshu’s managed-doom source port. Sinshu’s source port was written in the Unity-compatible C# language, and xabblll’s project got Doom running within the Unity editor. Squaresweets then brought it across the finish line to run in an actual Unity game.
You’ll need a .wad file of a version of Doom 1 to supply the art and assets for Squaresweets’ ultradoom.wad—at the time of writing, Ultradoom does not support any user-made projects like MyHouse.wad. That DOOM.wad can be sourced from a retail copy of Doom—I pulled mine from the Nightdive re-release—or the shareware version, which you can still get for free on the DoomWorld forum. Installation also requires the BepinEx Unity modding utility. Here’s the quick and dirty:
- Uh, purchase and install Ultrakill first. That’s important.
- Download the latest version of BepinEx—check your system information, but on Windows 11, you’ll probably want the win_64 version.
- Drag the files to your Ultrakill install, default C: / Program Files(x86) / Steam / steamapps / common / Ultrakill. Run Ultrakill once to complete installation.
- Download UltraDoom (click the green “Code” button then “Download ZIP”), put ultradoom.dll in [your path] / Ultrakill / BepinEx / plugins.
- Create a new folder, “doom,” in the same location. Drop ultradoom.wad (from the mod) and DOOM.wad (from your copy of Doom) in this folder.
- Play by clicking the smiley face in the upper left corner of the terminal touchscreen.
And you’ve got Doom, in Ultrakill. It’s full retro keyboard-only controls (WASD/arrows to move and turn, Ctrl to fire), the way god intended. Your mouse still controls V1 in Ultrakill, and you can look away from the screen to stop playing—just like real life! The mod has even been shouted out by New Blood honcho Dave Oshry.
Whether it’s Yakuza games offering bafflingly good emulation of Sega arcade classics, a Johnny Silverhand skin of Wolfenstein 3-D in Cyberpunk 2077, or that weirdly addictive ARPG you could play in Night in the Woods, the game-within-a-game is a gag I’m always delighted to see. As for Ultrakill itself, development continues on the influential, acrobatic shooter, with its next layer set to release in the first half of 2026.
You can now play DOOM on the terminals inside ULTRAKILL.
#DoomRunsOnEverything— @dave.newblood.games (@dave.newblood.games.bsky.social) 2026-02-08T20:25:13.654Z
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