<P> The single - player campaign includes thirteen hidden "death cards", denoted by playing cards attached to makeshift war graves . There is one in each level (barring those that take place in vehicles); collecting them unlocks cheats for Co-op mode, such as reduced enemy endurance and "paintball mode". </P> <P> World at War's multiplayer experience resembles the one established in Call of Duty 4: Modern Warfare . All versions of the game use a similar perk and ranking system and feature six multiplayer modes, including team deathmatch and capture the flag . There are three "killstreak rewards" that can be used to turn the tide of battle: a recon plane, showing opposing players on the mini-map; an artillery strike upon an area; and attack dogs, which spawn and attack opposing players . These are gained with 3, 5, and 7 kills, respectively . They are available in all game modes, apart from team survival, and cannot be edited . </P> <P> The game also features a cooperative gameplay mode with up to two players via split screen on consoles, or four players online, for the first time in the franchise . The Wii version of the game does not include online co-op, but two players can play through a "squadmate co-op" mode which allows both players to experience the game through the same screen and point of view . </P> <P> All versions except the Wii feature the minigame Nazi Zombies, which consists of 1 - 4 players fighting an unlimited number of waves of Nazi zombies . Players can work together with other people to assassinate the zombies in a "co-op" (cooperative) mode either offline with two players or online with 2 - 4 players . The players gain points by injuring or killing the zombies or repairing boarded - up windows, which are used to remove blockages inside the bunker and to gain access to more useful weapons than the starting M1911 pistol and unlock more rooms . Zombies continually break the windows to gain entrance and to find and beat the players; when all players are damaged enough to fall, the game is over . Three extra maps for the Nazi Zombie game mode were added with the World at War map packs . These maps, Shi No Numa, Zombie Verrückt and Der Riese added on to the Nacht Der Untoten map which came with the game . </P>

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