Oh uh, RUN IF YOU WANT TO SAVE YOUR FINGERS Mod for Friday Night Funkin' that adds custom weeks, game mechanics and an RPG side-quest.
Built on top of Psych Engine - https://github.com/ShadowMario/FNF-PsychEngine
Build instructions are all on the official FNF repository - https://github.com/ninjamuffin99/Funkin