Very good
Reviews for "WW2 Last Defense"
It was good, but it didn't seem like the speed increased enough. Also you might want to implement some type of regeneration of health, maybe a set amount at the beginning of each wave or you can purchase it before instead of an upgrade.
It's not too bad. For a simplistic game it's kinda fun, and you actually threw in upgrades only making it better. I just think there's more that could be added, but this doesn't seem like something to blam.