I LOVE "die and come back permanently stronger" type games! This is quite fun, with fantastic art!!
I have a few thoughts:
I'd love to be able to buy upgrades between waves, but failing that, I think it would be nice if the early waves could be skipped or sped through somehow once you get strong enough.
And I would spend $1000 on a "shoot diagonally" upgrade, haha.
But this is clean, polished, and very well-executed! Awesome job!!