Four weary humans work together in an apocalyptic world overrun by grotesque zombies, collectively known as the "infected," in this sequel to 2008's third-person shooter, Left 4 Dead. In addition to the new protagonists and five new campaigns, the game offers more enemy types to battle and adds a slew of weapons to improve your chance of survival. Joining the hunters, tanks, smokers, and boomers from the first game are jockeys, chargers, and spitters. Jockeys are short creatures that leap on the backs of characters and steer them toward dangers. Chargers are hulking brutes that run quickly toward characters and use their powerful arms to slam victims to the ground. Spitters spew out projectile acid that can also form deadly pools on the ground.
Each campaign area, ranging from a Coney Island-style amusement park to a Louisiana bayou, also contains distinct enemies to face. The "Dark Carnival" campaign, for example, features zombies wearing clown makeup, while "Swamp Fever" features creatures known as mudmen. New weapons and tools include a katana, baseball bat, grenade launcher, hand axe, Desert Eagle, military sniper rifle, chainsaw, MK17 assault rifle, and a defibrillator to revive fallen foes. In addition to the co-op campaigns and both the survival and versus modes from the original, Left 4 Dead 2 introduces a new multiplayer mode entitled "scavenge." As a survivor, your goal is to locate and collect 16 gas cans on each map before time expires, all while user-controlled members of the infected try to thwart your progress.