Far from a disaster! An excellent proof-of-concept for a very interesting idea :)
Regarding the presentation of keys/notes, perhaps give the icons some sort of arrow shape? Also FWIW, I think most rhythm games (or at least DDR and Pump It Up, off the top of my head) present directions in the order of left, down, up, right.
Totally reasonable to stay focused on Ao. Hope that's going well!
The Mac stuff is annoying... I've definitely had issues with Godot builds. I've yet to get a web export working, so I'm curious how you've been doing it. TBF, I haven't dug into it too much yet though :P