Bridge

Bridges are structures that can be built on water to allow fast movement and the construction of light buildings.
== Acquisition ==
 They can only be constructed on the following terrain types:
* Marshy soil
* Mud
* Marsh
* Shallow water
* Shallow ocean water
* Shallow moving water
* Chest-deep moving water
In addition, if the map tile contains both a road and river, then bridges will spawn on the river.
== Summary ==
While structures, bridges act similar to a floor tile. Unlike the water they're built on, bridges don't penalize move speed, making travel faster. They can also support structures that require a terrain affordance of "light", such as wooden walls and buildings, but not structures that require medium or heavy terrain affordance, like any other type of wall. Floors cannot be constructed on top of bridges.
The terrain types that allow bridges do not allow floors. If the terrain is unsuited to a moisture pump, or pumps are unavailable, bridges are the only way to improve the movement speed, cleanliness and beauty of such tiles or enable them to count as "floored" for the bedroom and throne room needs of a pawn with a noble title.
Bridges can be damaged or destroyed by fire or explosions. Only bomb type explosions will directly destroy bridges (eg Frag grenades), however fire explosions (eg Incendiary launcher) and vaporise (eg Diabolus) will spawn fire and so will destroy bridges indirectly, and will still have to be looked out for. When destroyed, whatever is built on top will be destroyed alongside it. 
Bridges can also be removed from the "Remove Bridge" gizmo under Architect/Structures.
== Analysis ==
Bridges are essential if you need certain objects on water, marsh or mud, such as wooden walls. Bridges can also support moisture pumps directly over water, allowing them to more efficiently remove the water than if built on the shore. And due to the faster move speed, you can speed up colonists by placing bridges through their path. Raiders can also path through the bridge, giving you some control over their movement.
In practice, raiders will not attack any wall or door unless:
# They are sappers or breachers; or 
# They have no reasonable target to access to without breaking a wall. 
Therefore, wooden walls are relatively safe to use. For example, bridges and walls can be used to surround your watermill generators, making them almost non-targets for raiders.
Power conduits can be built on bridges, replacing the need for waterproof conduits. The latter costs steel, which is 10x more than a regular conduit. However, the bridge has its own wood cost, and bridges are much more vulnerable to fire.
=== Path baiting ===
Because bridges have a significantly lower pathcost compared to water and mud, raiders will naturally prefer to path over most bridges but will also not attract attacks from breachers like walls used to constrict passages. This can be exploited by placing traps on the bridges for raiders to trigger. While spike traps will work for this purpose, IED traps are particularly effective especially when paired with a large roof supported by a wooden wall that will be destroyed by the IED's detonation, dropping the roof on the enemies for additional damage. 
This strategy works even if the bridge does not cross the entire span of the water, as even the small improvement in path cost is often enough to tempt raiders to use them.
== Version history ==
* 1.2.2753 - Can now be auto-rebuilt.
Category:Structure