Escalating levels of FPS turducken.
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.

A solid budget trackball, Logitech’s wireless Ergo M575S delivers much of the comfort and core performance of the company’s stellar MX Ergo S for about half the price.
Logitech makes some of the best desktop input devices, but they aren’t always cheap, with flagship models fetching over $100 at full price. Then there are more approachable models like its Ergo M575S, a budget-friendlier alternative to Logitech’s latest trackball, the Editors’ Choice-award-winning MX Ergo S. The M575S costs about half as much as the manufacturer’s premier model. This boiled-down version of Logitech’s ergonomic trackball handles the basics well enough, but it misses out on some cooler Logitech features, mainly centered in its software. (Too bad; they wouldn’t have cost the company much to include.) We maintain the MX Ergo S as our top trackball pick, though the Ergo M575S will serve budget buyers well enough.Design: Familiar Shape, Fewer Frills
Aesthetically, the M575S isn’t terribly different from its more expensive counterpart, the MX Ergo S. Its 1.9-by-3.9-by-5.2-inch (HWD) shell curves inward to fit right-handed users (sorry, southpaws), and is canted about 5 degrees off your desk to help prevent wrist strain. However, the M575S’s shell lacks the MX Ergo S’s grippy texture and additional tilting options.
The M575S also copies the MX Ergo S’s layout. A pair of additional buttons sits to the left side of your index finger, and a simple textured scroll wheel splits the main inputs. Unlike its fancier version, the M575S lacks directional tilt-scrolling for its scroll wheel, and it doesn’t have the extra single thumb button above its trackball.
The M575S has one small advantage over the Ergo S, though: its possible color palette. Instead of the default matte gray, the M575S offers five shell-and-trackball combinations to choose from. While your options are limited to blue, white, black, or gray, it made me wish the Ergo S had similar customization choices.
As for the power source, the M575S runs on a single AA battery and doesn’t offer wired use or USB-C charging. The device pairs with your device via Bluetooth or the Logi Bolt unifying USB-C receiver, which can be shared with some new Logitech peripherals to provide 2.4GHz radio-frequency (RF) connectivity.
I lament any accessory that uses disposable batteries or ergonomic devices that lack adjustment options. But on the flip side? Less heft. The M575S is about half the weight of the MX Ergo S, and light enough to be considered portable, provided you don’t mind the bulk of a trackball stuffed in your backpack.Testing the Ergo M575S: My Fingers Say It’s Well-Rounded
Unsurprisingly, my experience with the Ergo M575S was very similar to my time with the MX Ergo S. The two main buttons use the same switches as the Ergo S and provide a satisfying tactile response while remaining virtually silent. That’s a nice addition for anyone who wants to avoid making much noise in a co-working space.
I missed the additional body tilt the MX Ergo S offers, but the M575S is still one of the most ergonomic input options I’ve used in years. It might take a little getting used to if you’ve never used a trackball before. But I’d still recommend the M575S over something like a vertical mouse if you need relief from repetitive stress or other symptoms aggravated by poor wrist posture. A trackball like this reduces the wrist motion associated with mouse use. Wrist-pain sufferers may want to consider, however, that the MX Ergo S lets you pivot the trackball’s body to elevate your hand closer to a perpendicular position relative to your desk surface, more of a “handshake” grip. It all comes down to personal comfort.
Trackballs need regular cleaning to perform their best. Like other Logitech trackballs, cleaning the Ergo M575S is a simple matter of popping out the ball and using a cotton swab to clear any buildup on the rollers or sensor. While the tracking resolution of the sensor is fine enough to let you quickly sweep across multiple monitors, like other trackballs the Ergo M575S can have some difficulty handling pinpoint, precision applications like Adobe Photoshop or DaVinci Resolve, at least without practice.
I reflexively grouse about a peripheral that uses disposable batteries, but to its credit, the Ergo M575S is remarkably power-efficient. Even after several weeks of testing, the AA cell still registered a 100% level in the Logi Options Plus software.Software: Can’t Seize the Actions Ring
Speaking of the Options Plus software: It’s a well-rounded and functional customization suite for adjusting Logitech peripherals. It lets you record macros, adjust sensitivity settings, or remap inputs. Its most novel addition, the Actions Ring, isn’t available on the Ergo M575S, though. On the MX Ergo S, the Actions Ring, when triggered, pops up a small, round menu around your on-screen cursor. The menu has up to eight selections, and each selection can include nested functions, drastically increasing the number of macros and shortcuts at your fingers.
That’s disappointing, because it would’ve been a simple matter to remap one of the Ergo M575S’s existing inputs to pull up the new feature. This feels like something that could be easily fixed with a future software/firmware update, but it currently comes across as a bit of an arm-twist on Logitech’s part, to spur power users to buy the pricier MX Ergo S.