I really love this entry, pretty much gave a perfect score! I have a couple of suggestions:
1. The hitboxes & hurtboxes need to be a bit smaller, usually in a bullet hell game they are really small and it gives the player the feeling of near avoiding things when they probably didn't.
2. The projectiles need to have more contrast with the background. Typically in a bullet hell they have high contrast so you don't need to focus on them but can still tell where they relatively are.
Otherwise, I'm bookmarking this game... It's a ton of fun! I love the upgrade system and the bird theme.