Very fun game! I ended up relying on the cannon a lot, if only for the fact it was just the most consistent upgrade in terms of damage output and it doesn't require you to play as close to the enemies (felt hard to justify the risk given how scarce healing felt). If nothing else, I wished I could've played a lot more and hit a higher level (I think I got as much as 16), but the game lags once there are too many enemies, so I stopped being able to tell what was going on past that point ;P