its A LOT bigger, alot more complicated stuff such as linking all 3 teleporters to 1 mainframe just to use pack a punch
dogs and zombies start to come out together when ur in the higher rounds. monkey bomb rocks, i think the map is just a tad complicated, u open something, walk thru a door and see a bridge, and a ledge to jump off, and to get back up you gotta go alllll the way around to go upstairs, the dogs last way longer.
in a few words : its bigger, harder, but fun as hell