So this game is really neat and I think the concept is solid but I would want more polish. The timing can be really difficult to get back into if you get off because there's nothing visually or audially that can get you back on beat if you screw it up... I don't like to have to rely on visuals for getting back in after a mistake. The other part can help but it's not always that easy.
I really liked the battles other than that, they felt very good, a little skewed to the too easy side on the first two but pretty nicely balanced on the last guy.
Overall, great work!