Once they have been built, certain construction sites (like the Great Pit, for example) can be upgraded. Each day, the citizens can vote for one, and only one upgrade. Citizens should vote for whichever upgrade is more useful for the town.
Just before the midnight attack, the upgrade which has received the most votes is accepted and constructed immediately. In cases such as the Great Pit, the defense bonuses will immediately take effect on the day it's upgraded (Example: Your town defense is 200 on day 3, if your town decided to upgrade the Great Pit from level 0 to 1 on that day, by the midnight attack, your defense will be 213 due to the Great Pit upgrade). As a side note, the defense bonuses will not be added up in your town overview until after the midnight attack.
Upgrades are free : they require neither AP nor resources.
Each upgrade can be improved up to 5 times, each level being increasingly powerful. These upgrades can have numerous effects on a town.
Workshop[]
Level 1: The cost (AP) of all construction projects is reduced by 7%.
Level 2: The cost (AP) of all construction projects is reduced by 14%.
Level 3: The cost (AP) of all construction projects is reduced by 21%.
Level 4: The cost (AP) of all construction projects is reduced by 28%.
Level 5: The cost (AP) of all construction projects is reduced by 35%.
Watchtower[]
Level 1: Every morning, all zombies within 3 zones of the town are detected
Level 2: Every morning, all zombies within 6 zones of the town are detected
Level 3: Every morning, all zombies within 10 zones of the town are detected
Level 4: Every morning, all zombies within 10 zones of the town are detected + Allows citizens within 1 km of the town to return without using any APs.
Level 5: Every morning, all zombies within 10 zones of the town are detected + Allows citizens within 2 km of the town to return without using any APs.
Search Tower[]
The search tower originally starts with a 25% chance to undeplete an area.
Level 1: 37% chance to undeplete an area.
Level 2: 49% chance to undeplete an area.
Level 3: 61% chance to undeplete an area.
Level 4: 73% chance to undeplete an area.
Level 5: 85% chance to undeplete an area.
Pump[]
Level 1: 20 rations of water are added to the well (Once only)
Level 2: 20 more rations of water are added to the well (Once only)
Level 3: 30 more rations of water are added to the well (Once only)
Level 4: 30 more rations of water are added to the well (Once only)
Level 5: 40 more rations of water are added to the well (Once only)
Great Pit[]
Level 1: Increases defense of the Great Pit from 10 to 23
Level 2: Increases defense of the Great Pit from 23 to 44.
Level 3: Increases defense of the Great Pit from 44 to 86<--incorrect from here on).
Level 4: Increases defense of the Great Pit from 86 to 119.
Level 5: Increases defense of the Great Pit from 119 to 170.
Defensive Focus[]
Defensive Focus without upgrades makes defensive items worth 2.5 points each.
Level 1: Defensive items are worth 3.2 points each.
Level 2: Defensive items are worth 4.4 points each.
Level 3: Defensive items are worth 5.6 points each.
Level 4: Defensive items are worth 6.8 points each.
Level 5: Defensive items are worth 8.0 points each.
Water Turrets[]
Water Turrets provide 60 Defense by themselves. Please note that if you do not have enough rations in the well to operate the turrets, the turrets will only provide 60 Defense.
Level 1: Increases Defense from Water Turrets from 60 to 108, but consumes 2 rations of water from the well.
Level 2: Increases Defense from Water Turrets from 108 to 156, but consumes 4 rations of water from the well.
Level 3: Increases Defense from Water Turrets from 156 to 204, but consumes 6 rations of water from the well.
Level 4: Increases Defense from Water Turrets from 204 to 252, but consumes 9 rations of water from the well.
Level 5: Increases Defense from Water Turrets from 252 to 300, but consumes 12 rations of water from the well.
Upgradeable Wall[]
Level 1: Increases Defense from Upgradeable Wall from 15 to 51.
Level 2: Increases Defense from Upgradeable Wall from 51 to 86.
Level 3: Increases Defense from Upgradeable Wall from 86 to 123.
Level 4: Increases Defense from Upgradeable Wall from 123 to 182.
Level 5: Increases Defense from Upgradeable Wall from 182 to 243.