Left 4 Dead

The catch is that the doors to the save rooms can only be opened once by each character, and once closed, they cannot be reopened. This forces the team to work together or make difficult decisions about who to leave behind or fight alone. The game also introduces various special zombies, including the Hunter, Tank, and Boomer, which add an extra layer of danger to the gameplay.

Players can choose to play through the campaigns with AI-controlled teammates or with human players in co-op mode. However, the multiplayer offers a unique twist with the "Versus" game mode, where four players take on the roles of zombies, trying to eliminate the survivors. This adds a new level of competition and strategy to the gameplay.