About
Mushroom Kingdom Fusion is a free, non-profit Mario fan game that crosses the Super Mario formula over with elements from more than 30 other video game franchises, featuring numerous playable characters, hundreds of levels, and a large roster of bosses. Started in 2007 by the developer known as EddyMRA (formerly JudgeSpear) and built in GameMaker on a heavily modified open-source Super Mario Bros. 3 'Hello Engine 3', it grew into a long-running community project under Fusion Fangaming.
The game has had a famously troubled, on-and-off development history but resumed yearly updates, with later builds released through itch.io. It is unofficial and unaffiliated with Nintendo, and was never sold commercially.
Identity
Launch
- Binary
- MKFusion.exe
- Options
- %command%
- Needs files
- none beyond the binary
Proton
- Version
- GE-Proton
- Winetricks
- —
⚙ Setup notes
ProtonDB / Deck: Not on Steam (free fan game), so no ProtonDB rating. The creators state on itch.io that it is confirmed fully playable in Wine and Proton, including on Steam Deck. GE-Proton is the safest pick for an older GameMaker title; stock proton_experimental also works.
Install method (portable, no installer): Download from itch.io as .7z archives and extract with 7-Zip. You must grab BOTH the *"GAME ONLY"* archive and the *"MUSIC ONLY"* archive — extract the Music folder into the game directory or you get no music. Then add the extracted MKFusion.exe to Steam as a non-Steam game and force a Proton version.
Controller: Native gamepad support (the in-game options menu has controller config). No Steam Input mapping required, though you can add a layout if you want menu navigation on the Deck.
Note: The base game name is confirmed via the MKFusion.ini settings file it generates; the launcher executable is MKFusion.exe.
The one thing to know
Free fan game: by Fusion Fangaming (creator EddyMRA), distributed on itch.io — unofficial and not affiliated with Nintendo, never sold commercially.
Two downloads required: the *GAME ONLY* archive plus the *MUSIC ONLY* archive (current build V0.93, Rev D hotfix). Missing the music archive = silent game.
Portable: No installer — extract the .7z and launch MKFusion.exe. Add it as a non-Steam game and force GE-Proton.
Community guides
Write-ups and threads from people who got this (or a similar) game running. deckport links to them — it doesn't reproduce them.
Get the artwork
deckport never hosts game images. Open this game on SteamGridDB, pick
the cover / hero / logo / icon you like, and drop them into the
game folder under .deckport-art/ before you push it to the
Deck. The importer files them under the right names automatically.
Run it on your Deck
Two files: the one-time importer (deckport.py) in your
Deck's home folder, and this game's install helper. Copy the game
into ~/Games and run the helper with Steam closed — it
writes the recipe (binary, launch options, Proton version)
and registers the shortcut with artwork.