Multiplayer
Split Screen
There is currently a local multiplayer in the game which allows you to survive (and die) together with up to 4 friends on one machine!
However, it is in experimental testing (expect bugs) and there is no character creation for the other players. Also, it is best played with an Xbox360 Controller, as the layout and prompts are the same.
To start a split screen game, select a game mode as per normal. Once the first player spawns, press (A) on the controller, and you will be given the option to either "Take over player 1", or "Add new player". Choose "Add new player", then press (A) again.
As of 2013-10-21 Split Screen may be broken due to changes in getting the game ready for Steam.[1]
Lan/Online Multiplayer
It has been confirmed that co-op multiplayer will added after the game's initial Steam release.