Apart from exploring and killing zombies shutting down the towers is the main objective of the game.Each tower has a code that is found in your journal when picking up pages.When a tower is shut down a cut scene will be shown of the towers lowering itself.3 chests will be found in side the tower once shut down and contain a small reward.Nearly all towers will be radiated and will be home to hostile mobs.The centre Island is by far the most dangerous.Once shut down a huge reward will be found in the yard and multiplayer mode will be enable.A cut seen will show and the credits for the game will show.Currently multiplayer mode is disabled on ios due to bugs.