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. The last stage in each campaign has an expanded ending called the Finalewhich usually ends with players escaping on Rescue Vehicles like boats, helicopters, etc. The Survivors play through each chapter, making their way from safe room to safe room.
In Campaign mode, one or more players play as the Survivors, with the rest of the four filled in with AI-controlled 'Bots'. Each chapter ends in a safe roomwhich acts as a checkpoint that is triggered when all living Survivors get inside the safe room and close the door behind them. There are four difficulty levels : Easy, Normal, Advanced and Expert. During Campaignalso known as Co-opup to four players work together to try to reach the end of the campaign by fighting their way past large numbers of AI-controlled Infected.
