23a:Bridge

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Bridges allow dwarves, traders, and their cargo to travel over terrain that would normally be impassable. Bridges can be placed over Template:Ls and other water (as well as the ice sheet in some freezing maps), swamp tiles, Template:Ls, Template:L, and the Template:L. They can be made of raw Template:L, Template:L, Template:L, or Template:L of any material. Template:L can only be bridged by a Template:L or Template:L bridge. However, the topmost material in the list determines the overall material of the bridge: for example, you can use a single steel bar and four brass bars to cross the magma river.

Bridges built within the mountain can be attached to Template:Ls or Template:Ls and made to retract or raise. These can be used either to deny passage to enemies, or to kill them: a drawbridge lowered on any creature will kill it instantly. Moats (built from channels/Template:Ls) and "Trojan Horse" entrances spanned by a bridge are both very effective forms of fortress defense.

Bridge construction requires Template:L and a dwarf with the appropriate Template:L enabled (Template:L, Template:L, or Template:L), depending on the material that is used.

Types of bridges

When a bridge is placed outdoors, it is just an ordinary bridge, and cannot be assigned any special types. When built underground, however, a bridge can be either retracting or raising, like a drawbridge. Retracting bridges can be built without the need for an open area on the other side, while raisable bridges can crush anything they are lowered over, and will form a sturdy blockade against flying or aquatic assault while raised. In either case, the bridge must be linked up to some form of a trigger via Template:L for it to move; normally, this would be either a Template:L or a Template:L. When placing a bridge, press w, a, x, or d for a drawbridge in one of the four cardinal directions, or s for a retracting bridge (the default). The direction that a bridge raises can be slightly confusing: If a bridge raises to the left, then it forms a wall on the left side when raised, and when lowered it will squash anything to the right.

Even if a bridge is raised or retracted, you can not place (build) anything else in the space the bridge normally occupies. So a pressure plate to lower a bridge onto enemies can't be placed underneath the bridge area itself. You can build bridges over channels (for instance, to span a moat), but only after the channel is filled or "muddy" (from a prior filling). You cannot build a channel beneath a bridge after the bridge has been built.

Bridges as traps/weapons

Any Template:L (including dwarves) caught under a drawbridge when it lowers will be killed instantly. The creature will completely disappear, leaving neither a corpse nor any of its gear. Creatures caught on top of a drawbridge when it raises will be sent flying through the air, much like a catapult stone. In the words of Toady One, "The relevant function in the code is called flingify."

Note that bridges built outside the fortress gates cannot be linked to levers to be used as goblin smashers.

Bridge sizes

When building a bridge, you can select a number of pieces of material. Each piece of material increases the number of squares the bridge can occupy, up to a limit of 10 squares in width or height.

For raw stone, stone or glass blocks, and wooden logs:

• Size of Bridge = (Material Amount) x 4 - 1

For metal:

• Size of Bridge = (Material Amount) x 2 - 1

When sized and placed, the dwarves will only use the minimum amount of material needed. For example, if you want a 5x2 bridge, and select four stone blocks to build it with, the dwarves will only use three of the blocks.

Bridges can mix material types (stone, metal, wood, etc.) and gain no benefits from using only one type of material, but the color (and material for game terms) is determined by the topmost selected material from the material selection list.

Known Bugs

Bridge construction may generate a path-finding error if a dwarf attempts to use a chosen piece of stone that is inaccessible. To work around this you can use a different kind of rock.

Another common cause of path-finding errors is attempting to build a bridge in such a way that it would cover inaccessible loose rock or other materials that the architect would need to move out of the way. This often happens when a temporary bridge is built across the river or chasm, space is mined for the "real" bridge, and the temporary bridge is then removed. To solve this, leave the temporary bridge up until the main bridge has been fully designed by an architect.

If a bridge over the chasm or river has an item on it, and that bridge is removed, the item will stay there hovering, blocking all attempts to build another bridge there.

Admiration

Bridges, along with certain other Template:Ls, may cause happy Template:Ls for dwarves that pass by them. Comments that your dwarves may have about your bridge can escalate from fine, to great, to completely sublime. The better the bridge, the happier your dwarves. Building a bridge using smoothed blocks, metal bars, or glass blocks increases the value of the bridge making it much more likely to evoke admiration, as will using a highly skilled Template:L and Template:L/Template:L/Template:L.