Plays inside your own copy of Ultrakill, on your device, not in a browser tab. Opens github.com in a new tab.
How to play
Have your own copy of ULTRAKILL installed: the mashup plays inside it.
There is no release yet: get its code from its repository on GitHub and build it as its README says (it runs on Linux).
Install it as its page says. What it asks for is just below, in the list's words.
Start the game the way its page says: some mashups come with a launcher of their own.
What it asks for
ULTRAKILL (Unity 2022.3 Mono) with BepInEx 5.4.23.2 win_x64, Minecraft 26.3 with Fabric, your own copies of both games and a build from source; the README says the author develops on Linux with ULTRAKILL under Wine and native Windows is supported in code but untested.