This was very fun. It's a bit unforgiving, but at least it was a challenge! The visuals were fantastic too, I love the pixel art, and the main character is super-cute. There's an amazing amount of content there for a jam game - all the different enemies, and a decent amount of levels to play. It's an impressive feat for two weeks' work!
Most of all, I loved the concept of jumping on the beat, it really added to the rhythm-based aspect of the gameplay . There were a few rough edges around the implementation, though they didn't spoil it for me. It's a shame you decided not to do a post-deadline update to polish it up a little though, as I think it deserves the attention!