The idea is great! But the game's a bit too short :( Also, it's weird because the game actually gets easier as it goes, because your tank gets stronger. Except for the boss part, that's pretty hard.
I think it might be good to have a "New Game+" sort of thing in this game. Basically, play the same game again, but without losing any of the upgrades. It's a thing in some RPGs.
Overall a solid entry to the jam!