Bunker

"A fortification built into the ground that can be extended or upgraded into other structures."

- In-game description

The Bunker is a player made rectangle structure, partly in the ground. There exist 3 tiers of bunkers; the first is dug with a Shovel, the second is upgraded via Basic Materials and the third tier costs Concrete Materials and a significant amount of time to cure. They can be upgraded with add-ons or converted to other types of structures like garrisons. Bunkers can also be connected to Trenches.

Description
The Bunker can be made by equipping a shovel and opening the build menu (default: B). You can rotate the bunkers as you would with normal structures, but it can also snap to bunkers or to trenches (hold to disable snapping). If you directly join two bunkers together, the wall between them disappears and the two sections become one single structure with shared health. If one of the parts gets destroyed, they all get destroyed.

There is no limit on the amount of bunkers you can link together, however, their Structural Integrity will decrease. This results in the structure having less health; the health of a 2-bunker structure is lower than the sum of the health of two separate single bunkers. The Structural Integrity will decrease quicker for low tier bunkers than for higher tiers.

Bunkers can be repaired using a hammer and Basic Materials. Upgrading a T1 bunker into a garrison or into Tier 2 requires Basic Materials. Tier 3 bunkers require Concrete Materials.

Bunker Corners are an alternative type of Bunkers in a some-what triangular rather than square shape.

Structural integrity
When you go into the upgrade-mode, you can see bunker's approximate structural integrity in text such as high, medium, low, and critical.

The max health of a bunker structure is equal to the sum of the max health of each directly-connected bunkers multiplied by the structural integrity value. Factors affecting structural integrity include:
 * bunker tier (higher tier keep higher integrity)
 * number of connected bunkers (the more pieces, the lower the integrity)
 * number of bunker garrisons and engine rooms (they decrease integrity)

Factors that do no affect structural integrity: shape of the bunker and add-ons.

You should never let your bunkers reach Critical as your bunker's health and repair costs will suffer. Reaching Low is not advised, and adding more bunker pieces past Low integrity does not give more health to your bunker.

As a rule of thumb, tier 1 bunker should not use more than 4 pieces and never more than 7. Tier 2 bunker should not use more than 12 pieces and never more than 20. Tier 3 bunkers are such that the number of pieces is virtually not an issue.

Upgrading Bunkers
The hammer needs to be equipped to upgrade Bunkers. Press   to switch the hammer to Upgrade Mode. When next to a bunker, aim at it and press the "use" key (default keybind ) to open the bunker upgrades menu. For options that have a direction put your cursor on the particular option and use the  to choose the desired direction. Press  to select the option. If the upgrade is simply an add-on, it will be installed after your character does a short animation (and if you have the required materials). For other upgrades you must hit the blueprint with your hammer while having the required materials in your inventory. If the blueprint is shot before it is completed, it will turn back into the original building.

Add-ons
Similar to the Trench, the bunker can be upgraded with a set of add-ons. The upgrades consists of Pipes, a door and a firing hole. The latter two can be build on all sides of the bunker by scrolling the mouse wheel; the door requires to be connected to a trench. Building the add-ons is similar to upgrading, but when selected your character will go into a short construction animation after which the add-on will appear. The materials will automatically be taken from your inventory.

Modifications
Beside upgrading the tier or placing add-ons, the Bunker can also be modified. This ranges from adding a spawn point with the Bunker Base to adding active defenses, as well as placing the mighty Storm Canon. Below you can find a list of all the various modifications. It should be noted that some defenses cannot be constructed on all tiers. There is no way to remove a modification from a bunker. Placing a modification will erase all add-ons and infrastructure modification placed in that bunker; the spent materials will be lost.

When adding Garrisons to your bunker complex, be aware that they cannot be directly adjacent to each other. There can also only be one Bunker Base per complex.

Infrastructure Modifications
All other Modifications available are Infrastructure Modifications. A certain amount of those must be built in bunkers connected to or linked via trench to a Bunker Base as a prerequisite to unlocking bunker specific upgrades for that Bunker Base. Infrastructure Modifications comes in two types, "Command" and "Garrison", you need the correct type as prerequisite for certain bunker upgrades. Beside their type, all Infrastructure Modifications are functionally identical. They all cost 50 basic materials and can only be installed in Tier 2 and 3 bunkers. Infrastructure Modifications include toilets, lockers, beds, etc... the difference between each is purely decorative.



Bunker Husk
When a bunker is destroyed, it leaves behind a husk. The bunker can be rebuilt from the husk by using the hammer in upgrade mode and pressing. This will replace the husk with a bunker blueprint at the tier it used to have, for the cost of that tier (e.g. shoveling for Tier 1, Hammer and 75 bmats for Tier 2). All previously installed modifications and add-ons are lost and must be reinstalled after bunker reconstruction, at normal cost.

The husk can also be destroyed with explosives, to make space for different structures for example. The bunker husk has the same max health as the bunker it comes from. Or you can wait for decay to destroy it. Husk decay cannot be prevented and is usually the same speed as the decay near region borders.

Tips

 * Upgrading T1 Rifle Garrison to T2, T3 Rifle Garrison is cheaper than build T2, T3 bunker first and upgrade to Rifle Garrison. Upgrading T1 Rifle Garrison to T2 costs 75 Basic Materials and T2 Rifle Garrison to T3 costs 30 Concrete Materials like normal bunker does.


 * You can hold shift while placing bunkers to prevent them from automatically connecting to another bunker or trench.