This one was fun!
Though the difficulty could use some adjusting.
It gets very busy very quickly, and holy moly the whirlpools. The whirlpools are a nice addition, but they too, just like the enemies, get very overwhelming very quickly. But that's not necessarily a bad thing, that's just my opinion.
I especially liked the upgrading, if you decide to expand upon the game, I think it could lead to some very interesting mechanics or combinations.
Nice job!