>>63679956the easy part is creating the button maps for the songs you want once you have the system to put them in
the hard part is creating a precise rhythm game that responds to inputs with the correct timings, and with assets like character/boss/enemy/effect animations and sprites
I cant find it now but I remember reading an article by the creators of rhythm doctor and dance of ice and fire, who wrote about their process designing a system for detecting precise input timings, and I remember it looking not easy
maybe you're the technical sort who knows how to create that rhythm system, but then you also have to be someone with the skills to find artists and put together a team (or have those skills yourself), and also be willing to do that work for free as a holo fangame, and that combination is going to be pretty rare
https://nullrefrepro.itch.io/hinotori-rhythm one such person is nullrefpro for example but even this is a primitive version and you already know he's constantly busy working on other hololive projects which actually get commissioned 
