This is very close to an amazing game. Some detractions:
Why is the power-up "R" called missiles? When there is a power-up "M" for machine gun? Unnecessarily confusing. Especially since one is the best weapon in the game, and the other, the absolute worst. Not really balanced there.
Obvious bug: if power-up X drops, and I don't pick it up before another same power-up X drops, the second one doesn't increment / upgrade the weapon.
Annoying feature: the 'current song' pop-up is super distracting, given the intensity of the game and one-hit deaths.
What is the point of the impenetrable super-shield foes? Or the random epileptic screen flashes?
Also you will forever annoy every medal collector with that "be the top of the all-time leaderboard" medal. That would have made more sense with a 'top of the week' or something like that. The way it's set up is first-come, first-serve. Kind of frustrating. Maybe that's the point.
Good bullet hell upgrade top-scroll shooter.