Honestly I don't know how to do it. When I got to wave 7 I had Armada as a map. Even with helicopter support cleanup, I couldn't get out in time (no left Playtime) because of a Megaton. A player told me he reached stage 15. I can't even imagine. Because in stages 7 it's almost as if you get one-shot by zombies. It's fun to see the maps we play in multiplayer in a larger version with much more detail.