Missions

In the majority of the SAS: Zombie Assault series, the mission was to survive a certain number of waves of zombies. However, in SAS: Zombie Assault 3, a new mission was added: Purge mode. Players were to stop zombie nests from spawning zombies by shooting it to death. For beginners, Purge mode is very difficult because the nests have too much health and the zombies easily overrun the players.In SAS: Zombie Assault 4, however, each level has its own special mission, such as rescuing people or defend the civilians from zombies.

SAS 1, 2 and Insane Asylum
As mentioned above, the first games was only about surviving waves. Each game had a different map and zombies poured in for 30 waves. The point was to survive all waves.

SAS Zombie Assault 3
In SAS3, like earlier games was about surviving waves. However, instead of one level with 30 waves, there are five levels with 4 waves to start. The waves get longer and increase in number when the player ranks up. Also, there is Purge mode, which can only be played in Verdammtenstadt and Black Isle. In SAS3 Mobile, there are many maps with 5 in each region, Europe, North America, Russia, and China. Also, a new gamemode was added in 2012: Apocalypse mode. The objective is simply to survive an endless wave of zombies, which won't end until all players are dead. SAS3 is also the introduction of Multiplayer. In SAs3, 4 players are randomly selected to play one multiplayer mission, with a gamemode the player selected.