Once you get to the undead places, the enemies you face take several max-level towers to even think about killing, from wave 1. You should consider never making video games again you should get stuff for completing achievements. Also I think it's a very nice twist to normal tower defence games, and I especially like all the things that don't have to do with the game objective: killing sheep and goats, catching fish, freeing sasquatch etc.
 "Kingdom Rush"){kind=icon}
 "Raze"){kind=icon}