Editing v0.31:Bridge

{{quality|Exceptional|22:21, 10 November 2010 (UTC)}}{{av}}

'''Bridges''' are extremely useful buildings for crossing dangerous terrain and also for fortress defense. Using them to control [[flow|fluids]] can save a ton of mechanisms and time, especially when the fluid in question is free-flowing and not pressurized (by {{L|pump}}, {{L|river}} or hydrostatic anything) and needs a wide tunnel.

==Building Bridges==

Bridges can be built ({{k|b}} -> {{k|g}}) of {{L|metal}}, {{L|stone}} or {{L|wood}}. They are first designed by an {{L|architect}}, then require a specialist worker for the material used (e.g. a {{L|mason}} for a stone bridge). The size of the bridge can be altered with {{k|u}}{{k|m}}{{k|k}}{{k|h}} while placing it, up to a maximum size of 10 squares in each direction. The bridge must be anchored to a solid surface on at least one edge. Before placing the bridge ensure that the bridge raises in the direction you want it to using {{k|w}}{{k|a}}{{k|d}}{{k|x}} or retracts using {{k|s}}.

'''Materials'''
when choosing materials the order that they are presented on the list determines how the bridge will be labeled NOT WHAT ORDER YOU PICK THE MATERIALS! the highest one up on the list is the core construction material. this will define the color of the bridge (and possibly how fire resistant it is, although this hasn't been tested extensively). materials are placed on the list in order of distance. so simply make sure the primary material is the closest or at least closer than any secondary materials you wish to use. You will need number of tiles divided by four plus one ( Tiles/4+1 ) of material to build the bridge.

Material does not appear to influence dragonfire which will destroy bridges.  Some magma-safe materials including iron have proven non-resistant, (Needs further testing)

Big bridges can take weeks or even months to complete. You can shorten construction time by moving the materials to the site before starting construction, and by using blocks instead of rocks. While the material-gathering time is the same for rocks vs blocks, the actual construction is three times faster for blocks.

==Raising and Retracting Bridges==

All bridges in DF can be raised or retracted by linking it to a {{L|lever}}. This requires a {{L|mechanic's workshop}} and a dwarf with the {{l|mechanics}} labor activated. 

If a bridge is set to retract when the lever is pulled, the bridge essentially disappears dropping anything (friend, foe, or object) on the bridge onto whatever is underneath. Clearly this can be used to drop your enemies to rocky/watery/fiery deaths (or anything more imaginative you can think up!).

If a bridge is set to raise when the lever is pulled, the bridge becomes a {{L|wall}} along the edge selected with the {{k|w}}{{k|a}}{{k|d}}{{k|x}} keys when placing the bridge. The resulting wall is always one z-level tall, regardless of the length of the bridge. The wall acts as if it was {{L|construction|constructed}}, rendering it invulnerable to {{L|building destroyer}}s. {{Verify}} The bridge also "moves" to this position very fast, firing anything on the bridge into the air. The key advantage to raising bridges is the creation of a wall when the bridge is raised. This can be used to block fortress entrances/corridors. Using 2 bridges at opposite ends of a corridor creates a very large and simple trap by walling in enemies. Or... Smashing them to tiny bits if placed to raise facing eachother, with no space inbetween. For added effect, place {{L|pressure plates}} on both ends to raise the bridge when steped on, to fling them, if there is a {{L|floor}} directly above, they will be stunned, (If there is a floor beneath the brige) and if nobody is on the pressure plate, they have to be lucky to not be smashed on the floor when the bridges come down. (If there is no floor beneath the bridge) they will fall, sometimes into something {{L|water|very,}} {{L|magma|very}} {{L|megabeast|bad.}}

Walls cannot be built along map edges.  Because bridges can be built along map edges and then raised to act as walls, they can be used to control where enemies spawn on the map.  

The lowering of a drawbridge can also be used as a {{L|dwarven atom smasher|waste disposal}} for unwanted stones, {{L|refuse}}, {{l|goblin}}s (dead or alive), legendary {{l|cheese}} makers and {{L|nobles}}, to name a few. Even fluids get destroyed (this is especially useful considering lack of chasms in the new version). However, lowering a drawbridge onto a sufficiently large creature (such as a {{L|forgotten beast}}) simply destroys the bridge.

==Bugs==

Bridges will not operate if any one creature of size 1200000 is on them.  This weight limit is not cumulative - a bridge will still retract if a hundred goblins are standing on it, but a single rutherer accompanying those goblins will prevent the bridge from operating.  This limit is the same for retracting or raising bridges.

It is impossible to channel out stone that is directly under a raiseable bridge when its in the raised position.

Non-{{L|magma-safe}} bridges will heat up and eventually melt if the center tiles get covered in magma or exposed to {{L|dragon}} fire, whether the bridge is raised, lowered, or even retracted.

While bridges do not provide structural {{L|support}}, the game will still allow you to place unsupported {{L|construction}}s adjacent to them which will result in an immediate {{L|cave-in}} once completed, often tossing the unlucky mason off the edge to a horrible death.

A raised bridge cannot be linked to a lever from the inside - the mechanic must be able to stand in the center of the bridge.

==Strategies==

SELF CLEANING BRIDGE<br />

Ever have a horde of goblins sitting on your bridge and preventing you from admiring the elegant beauty of your entrance? I have a simple solution for you!!<br />

I know what you may be thinking,  "Could my bridge, with a dozen goblins standing on it, be raised?" The answer is yes!  A normal bridge can't!.  But, with a little careful design and some dwarven ingenuity, you too can make a bridge that will stop almost any foe!<br />

Step 1: Build a pit!<br />

Don't just build any pit; it needs a special shape for the bridge to function properly:<br />

EXAMPLE: x = channeled out section   . = solid ground<br />

<pre>
...EXIT....
.x.xxxx.x..
.x.xxxx.x..
.x.xxxx.x..
.x.xxxx.x..
.x.xxxx.x..
.x.xxxx.x..
.xxxxxxxx..
.xxxxxxxx..
.xxxxxxxx..
.ENTRANCE..
</pre>

 If this is your only entrance, be careful to leave ramps at the corners so your dwarves can travel through.<br />

Step 2: Bridges.  Plural. <br />

We will be making many small bridges.  Each letter designates an individual bridge (FIRE PROOF MATERIALS ARE STRONGLY RECOMMENDED).<br />

< > = bridge lifting direction  (A) = bridge "A"<br />
...EXIT....<br />
.x<A)(B>x..<br />
.x<C)(D>x..<br />
.x<E)(F>x..<br />
.x<G)(H>x..<br />
.x<I)(J>x..<br />
.x(KKKK)x..<br />
.x(KKKK)x..<br />
.x(KKKK)x..<br />
.ENTRANCE..<br />

Notice that "K" has no opening direction, because it needs to retract so you can use catapults or ballista to hit pests around the entrance.  In this design the exit bridges are all 3 x 1 in size.
This can be any length or width (up to 20 spaces wide). Only the basic shape is important.<br /></i>

Step 3: Arming the trap! <br />

This is the most simple step, but also probably the longest one.<br />

Link all of individual bridges to ONE lever.  Yeah, it takes a bit, but it's worth it.<br />

Step FINAL: Destruction. <br />

Wait for some unsuspecting victims to begin crossing your bridge, and then flip the lever. Getting proper timing down will likely take practice.<br />

Anything small will be tossed up into the air and then fall into your pit. Anything too large for the bridges to lift (titans) will still be trapped and waiting for your archers / siege weapons / other nefarious plans.<br />

DISCLAIMER: we are not responsible for inept or lazy dwarves that fail to operate the bridge. Standing on the bridge when the lever is pulled may result in injury or death. Many goblins were harmed during the design of this bridge... and some dwarves. 

SINGLE LEVER AIRLOCK<br />

Normally, bridges in open states permit movement, while bridges in closed states restrict it.  This can be irritating in the design of an airlock system, as such systems usually either require cumbersome logic systems or multiple levers to function correctly.  Using floodgates or hatches for these systems may be dangerous, as they are vulnerable to building destroyers.  Instead, consider the following design:


XXXXXXR____<br />
D_____/

The retracting bridge on the higher z-level is used not to permit access across a channel, but instead to block access to a ramp.  Thus, a single lever can be attached to both the drawbridge and the retracting bridge, preventing airlock vulnerabilities due to lever timing.  With a suitably long distance between the two bridges, the lever can be placed between the two, permitting easy movement of individual dwarves between isolated zones, via lever profiles.

{{buildings}}