I really like it!!! I disagree with some of what reidgillis said about difficulty. I think the difference from level 1 to level 2 is perfect for a tutorial/easy mode. Level 1 only has down-beats and Level 2 implements hitting notes on up-beats. I am gonna play Level 3 and see what that's like. This makes me wanna play some Muse Dash hahaha xD I haven't played that in what feels like years now ;o
Okay- my review of level 3 itself is that the sorta "swing" beats don't really "feel right" when split between two players. I think partially is due to the very quiet and fast drum-hit sound effect, but I think even if the sound "matched more" to make the rhythm clearer, splitting it between to characters will be tricky especially for these moments. I guess my suggestion there is to try to guarantee that both parts have their own rhythms that don't require hearing the other character's part to make it work. If that made sense hopefully.
Regardless, this is extremely impressive!! Music games feel so difficult to make honestly, I'm amazed with your team for pulling this off! :O I also love the cat sounds for "ready? ... start!" lol so cute xD