We're currently working on 2 new game modes called Classic Survival and Defense mode, both of these will support local co-op.
Classic survival is a lot like the old tech demo with the addition that you can choose your weapons and abilities before you start a round.
The defense mode has you defeat waves of enemies with a chance to buy upgrades and build defense structures in between waves.
Our plans are to release a first version of these around the end of this month, if people like the game modes we'll also be adding more maps to them afterwards.
There'll also be a smaller update next week which implements some of the still missing perks in the current campaign mode.