Plays inside your own copy of Minecraft, on your device, not in a browser tab. Opens github.com in a new tab.
How to play
Have your own copy of Minecraft installed: the mashup plays inside it.
Download it from its release page on GitHub (it runs on Windows and 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
Minecraft Java 1.21.1 with NeoForge 21.1.x and Java 21 on 64-bit Windows or Linux (macOS unsupported); the user supplies libretro cores, BIOS files (PS2, Dreamcast) and legally obtained ROMs.