I like it! Reminds me a lot of one finger death punch. A couple "notes" (music joke, get it?)
1. While I can pick up the beat from the music, it takes a little more effort for this game than with other games I've played. Rhythm games like this typically do better with an extremely distinct separation of beats. See Crypt of the Necrodancer for an example:
The bass in this song makes it extremely easy to pick out the beat, which dramatically increases the ease of play. Finding the beat should not be the part you want your player focusing on2. The beat counter you have works fine for a prototype, but if you want to improve the player's ability to read the beat, consider adding a visual cue that gives lead up. Again we can reference necrodancer for this (I've played more rhythm games than this I swear it just has good examples :P)
Note the heartbeat meter at the bottom of the screen. Allowing the player to anticipate the incoming beat visually is super helpful, particularly after they make a mistake and need to quickly get back on beat3. Having the player only do partial damage when they get "ok and good" hits feels terrible. Make it so the hit either connects or it doesn't, and rankings can be for points if anything. It just doesn't feel good to play with, and the game would be significantly improved without it.
Like I mentioned before, check out one finger death punch if you haven't already! Very similar in premise, there might be something there you could take from it if you choose to continue this!
Congrats on finishing the jam! I know I mostly critiqued with this comment so I'll reiterate: I enjoyed this game quite a bit! Rhythm games are great and the world needs more of them, so get on it!