https://store.steampowered.com/app/1585220/Melatonin/
Melatonin is a rhythm game about dreams and reality merging together. It uses animations and sound cues to keep you on beat without any intimidating overlays or interfaces. Harmonize through a variety of dreamy levels containing surprising challenges, hand-drawn art, and vibrant music.
There was a thread about this one not too long ago on one of the Steam Deck communities...hang on...ugh Lemmy search is the worst....ok found it!
Here it is from your lemm.ee pov: https://lemm.ee/post/922657
I think the OP came and joined this community too afterwards so they should be around somewhere if you're looking for more info than was in there 😄
It's me, hi, I'm the OP it's me!
Okay references aside, I'm indeed happy to answer questions about the game! Since my post they actually released an option to add your own music via a level editor which is cool. It does require you to have your own mp3s, to know the BPM of those songs and to have more patience than I have but it's a nice idea at least!
I recently also learnt that the game is basically made by just one guy which I find very impressive considering how polished it feels.