Multiplayer is just regular 4 player deathmatch, as well as team deathmatch. The game is NOT limited to 4 players, and the multiplayer is COMPLETELY customizeable by MODMAKERS. Thus, modmakers can have as many players as they want (up to 32 I believe) and the doors are wide open as to what they can do. I think a co-op mod would be sweet. Also, a Team Fortress mod is in the works, as well as a total conversion.