Pretty good game and the procedural aspect is really neat, the visuals are great too, as is the auto-aim setup (since let's be real, no one needs to aim when playing most bullet hell games, the focus is on dodging bullets)
The only main pain point I would say is that once you beat a group of enemies (or if you died), it'd be great if the bullets on-screen went away; as it is, it almost encourages me to kill all *but* one enemy, wait for the bullets to go away so I can get gems, *then* kill that remaining enemy, which kinda slows down the pace of the game some when I want to just blow everything up.
I'd even be fine with enemies coming in in waves automatically, instead of waiting until you kill the last enemy, to keep the pace of the game going; it would encourage players to wipe out enemies faster so they get that "bullet clear" which would only happen if all enemies were wiped out, before they got overwhelmed with enemies.
Also, as a suggestion, maybe the green arrow powerup could increase the % of gems dropped from enemies or your firing rate so players get something immediately tangible instead of a ??? factor that might not have an effect before they die?
Really nice job, deserved front page :)
EDIT: You know, it'd be really good if Newgrounds let us reply to replies to our reviews!
All that you wrote about in your reply though sounds like a really good idea , looking forward to your future games :D