it was good
but it lacked much after like the 4th level. the xp was so easy to get that i already had all the upgrades before i finished half the game! you should add more upgrades.
you could use a red rock smasher, a plasma drill or something that actually hurts them when you drill them, an ink spray to stun enemies, maybe a triple drill like 2 extra drills on your side that are smaller and dont go as far, when you kill an enemy they drop a temporary powerup that makes 2 fishes follow you and shoot automatically, and maybe an ultimate that like sends tentacles spiraling from behind him destroying all of the enemies on the screen, but you have to wait for a bar to fill up that fills up when you kill enemies or something.