Agreed with the previous comment. While it looks really nice, central idea is unclear. I guess attacking structures are planned too? Without removing the mobs it seems impossible at the moment. Maybe the idea was that you do not attack at all, only surviving time? Not sure. Also, I'd make it more obvious where the guys can and cannot walk. Are blocks with 1-2 trees passable? They can also be a curious obstacle, as you can't place a block where these small trees are, but mobs can traverse them alright