There's nothing that I could add here, everyone said everything that there is to say. Concept is great, you can make a great rythm game with it. Unfortunately, controls are the biggest offender here in my oppinion. It's difficult because of them really, they just don't feel right when following shapes on the screen. One thing I want to offer for the controls is to order them differently on the screen, something like letter C on it's back. Idk how to explain so here you go like this xd:
Q R
W E