Nice Dandy Game
Really great game. Good graphics, nice upgrades
Suggestions: Infinite upgrades (or at least infinite health upgrade) since once you get everything, the EXP is just there for no reason. Try to fill in the levels 8-13 because there are only like 3 enemies per level during that time. A grenade that explodes on impact (less damage) would be cool too.
Nice game though.
(Do a hybrid level up until you get 3 in everything (not in grenades) and then max out your weapon first.)