This is a cool concept! My combat skills are not great (I'm more of a tank type of player where I'm not so good at moving and not getting hit xD), but would be interesting to see where you take this after the jam.
Might be cool to have a little bit of the heartbeat mechanic built into the player character -- like lil tiny sparks on the beat, so it's a bit easier to time attacks if you're not super great at keeping a beat.