Fun game. The controls remind me of Death vs Monstars, one of my favourite web games.
I love shoot em ups and upgrade games, so this is just right for me.
Some criticisms though:
The difficulty spiked at level 4 for me - it took me many tries to beat that one, I felt like I just didn't haven enough firepower. The rest of the levels seemed balanced.
The survival mode at the end is quite boring. The enemies have too much HP and it's a chore to finish them off. I think increasing the enemy speed would be a better way of adding difficulty instead of HP.
Anyway, I'm looking forward to seeing what else you make!