I think you should add OST and camera shake sync with sound beat
(guess improvement)
Controls are too much physics based -> check this behavior:
1 ... smack mouse to walls
2 ... pivot is changed to corner
3 ... now <damage ball> moves based on your mouse location instead of charging up velocity
(this might has balance issues) -> limit time how much can you be clamped in corner
auto throw ball out on release or timeout
PS: Your concept is top notch in theme