No other player can join a Single Player game, unless locally (LAN), via the connect 'host local ip' console command. The player assumes control of one of the Survivors, and all the other characters are AI controlled. Single Player is a gameplay mode with only one player controlled character. Available in Left 4 Dead and Left 4 Dead 2 (Pre- The Last Stand Community Update)
Play a single player offline game with computer-controlled teammates.
