Thanks for the detailed comment!
Chart difficulty vs. the ease of actually winning is something I noticed myself, even as I've played it a hundred times during testing. There's no punishment for actually missing a note, and until I'm a better level designer I will keep it that way XD
I'll look into randomizing colors! Not sure what options Godot has for fonts but I too am not satisfied with the look of the hit grades.
Yeah, for now they gain a blush at a high score and look concerned/surprised when you miss a note. Could be fun to add expressions that adjust based on the meter! Only other thing that changes is the tail-wag/stroke speed when your combo is higher.
Good news about some of the bugs! In the version I'm working on, I've already fixed the lurch animations (as well as a few others) continuing to loop instead of resetting. Puer and I talked about unique animations for double-notes... we wanted to reduce the amount of work on his part so for now the most I think I'll do is make it so hits processed withing a few milliseconds of each other don't instantly change direction. And the animation resets whenever a note is hit has been fixed... although they can still end up playing a different animation >_>