Yes, that’s planned… but what’s going on with the music pricing on the store?!
This boss already has more health than usual (2x200K at 100% difficulty instead of 1x250K). It also depends on the weapon – if the boss is strong against it, you’ll have a hard time.
It always rotates 360o, but it starts from a random angle each time (which makes it seem like the circle isn’t fully completed)
Added to v.85 
Idea
Ugh. That would require a lot of texture space, and it combines very poorly with the ‘pain’ animation (in the last stage). Still, I suppose we could replace the pain animation with looking left-right right, that would probably work. Which one is more important, do you think?
No. What is you see is the guitar’s health bar, which is a bug. Fixed in v.85 Bug
No. Due to a lot of custom behaviour, it’s difficult to put it in. Plus, I think there would be too many projectiles to avoid 
Known. All syncing is done with counting frames (rather than monitoring audio), so it will drift away eventually. Low FPS makes things worse.
It already does that.
Agreed, but sadly that would require too many textures.
Because bug. Fixed in v.85 Bug
Considered this, but I don’t have a clean way of hitting one enemy but damaging another (“damage is still on the guitar”, as you say). Plus, the satellite is indeed spawned by the guitar (although I don’t think that would be a problem – satellites are not removed if they are outside the screen, and the bouncing code will eventually lead them back in)
Yes, I can. But that will create longer periods where the UCO is vulnerable (so the whole fight would be easier), so I’m reluctant to do this until some more people weigh in.
The type of Bezier curves used to control motion have the drawback that speed is not constant over them. I have fixed this for the galaxy, but it requires precalculations that are probably too expensive to perform in the middle of a wave.
Agreed. The clefs were only chosen because they are thin and long, which works well for this type of attack.
Quarter rests are not easily recognizable as music symbols. Perhaps a stylized 
would work better?
Same as any other boss. Now that you mention it, I have seen it appear a lot, but I can’t find anything wrong with the probabilities 