Very nice game, loved rhythm games for most of my life since OG guitar hero etc.
I did notice that some of the notes spawn ridiculously close together at times which when you are relying on a keyboard for input, even a responsive mechanical one, feels super punishing considering unlike guitar hero etc you don't rebound from misses by building a new combo (maybe this should slowly regen your life as you get more consecutive perfect notes). And the presence of these super fast button spammy sections felt more like luck as to you avoiding them showing up than anything else..
But I LOVE the idea of roguelite rhythm games and you had some great ideas for the upgrades. Nice job!