This mod is a co-ops mod. That means that you can play multiplayer in the singleplayer levels (You Cooperate with your friends on the internet or on LAN) A quick note on running a Co-Op server, this is a must! Please do not turn on Automatic Downloads. This will cause major LAG. You have been warned. Ping times will quadruple and you will no doubt sit and wonder why there is so much lag.