While this game is certainly fun, it has a massive flaw. The upgrades are pathetic, and I mean PATHETIC. After the first level or two in damage, I didn't notice any difference at all until the final level in it. I was clearly doing 2 points of damage after the firs upgrade, but didn't do 3 damage until the last level in damage. The same goes for decreased cooldown time, which was almost imperceptible until the final level in it. Decreased hitbox seems to be all but useless, and the regeneration upgrade seems like a waste of money past level 2. The only 2 I noticed major, clear-cut differences in were the health upgrade and the potion upgrade, which were both still pretty sad because your maximum HP is pathetic, considering how flooded by bullets the screen gets by world 2. That said, I did have fun, and this is certainly a good game. It just has a really big flaw.