Plays inside your own copy of Doom / Doom II (patched GZDoom 4.14.2), on your device, not in a browser tab. Opens github.com in a new tab.
How to play
Have your own copy of Doom / Doom II (patched GZDoom 4.14.2) installed: the mashup plays inside it.
Download it from its release page on GitHub (it runs on Windows).
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
Windows 10/11 x64, about 8 GB RAM, internet for first setup, your own Minecraft Java (26.3 with Fabric Loader 0.19.5 and Fabric API) and your own Doom/Doom II IWADs. The installer is unsigned and was not tested on a fresh Windows install.