This was an amazing little demo!
The art, music, and sound effects were all superb.
The difficulty was a little on the easy side, but i noticed all of the songs were marked beginner, so the full game will probably get harder.
My one complaint was that the key-mapping didnt seem to work right, and my controller (8bitdo sn30pro wired) didnt work, save for the rumble. But that will obviously be fixed by the full release.