Fantastic entry, I got to wave 37 so far. I think the core gameplay loop is one of the best I've played yet in the jam, and the expression of the invincibility theme was also one of the best with the "reverse bullet hell" gameplay.
Some constructive feedback for things you could improve if you keep working: The game feel / reactivity / juice wasn't bad, but I think it could be improved by adding things like some mild screen shake, some animations (even if just a single frame) when enemies get hit, little things like that. You're probably already aware of these kinds of effects and just didn't have time to work on it, just thought I'd mention it.
I think it would also be really neat to do a little more with the blocking bullets mechanic, like having it power up an ultimate move over time, or reward you with currency, anything like that.
Other things I did love: Lots of enemy variety for a jam game, I exclaimed out loud when the Nebuly boss appeared. The "pick one upgrade" system is always a welcome addition to games like this, and I enjoyed getting to customize my character build that way. Gives it a lot more replay value. Everything was very clear visually and behaved the way I expected it to, whenever I messed it up it felt mostly like a skill issue, not a problem with the controls or mechanics. The difficulty escalated at a very nice pace, started off easy as I got comfortable with the gameplay, and gradually got more challenging until I was really sweating trying to stay alive by the time the boss fight hit.
Awesome work!