Like bailman said, it starts out slow, but really hits the fan in the later waves. Despite that I ended up stopping at about wave 15, because I kind of got pretty much all I could out of the game by that point unfortunately. If something was shooting back at you, you had to replenish ammo, or could upgrade your turrets then I probably would have enjoyed it a bit more. Other than that, fantastic job! I especially liked the mini-map, it's a godsend because it saves you from just aimlessly wandering past wave 10, when there's always something to shoot.