Editing v0.31:Trap design

:''This page is one of several inter-related articles on the broader topic of defending your fortress and your dwarves. '''Trap design''' focuses on the theory and design of complex traps, mechanical systems and other automation for defending your fortress, and also on unusual uses of simple mechanic's [[trap]]s. For a general overview of the threats that will challenge your fortress and things to consider when preparing a standard defense, see the '''[[defense guide]]'''. For tips on laying out your architecture to protect your military, see '''[[security design]]'''. For specific advice on how to get your soldiers prepared for any threat, see '''[[military design]]'''.  See '''[[trapper]]''' for catching vermin-sized creatures in animal traps.

* For suggestions on disposing of nobles and other unwanted residents, see [[unfortunate accident]].

* For a basic overview of how the different machine parts work and work together, see [[machinery]].

Simple one-tile [[trap]]s* are just that - they exist only on their own tile, trigger themselves when a target walks onto that one tile, and affect only that one tile.  Complex traps and automation rely on linking [[door]]s, [[hatch cover|hatch]]es, [[floodgate]]s, [[bridge]]s and mechanic's traps to [[lever]]s or [[pressure plate]]s, along with [[machinery]] to provide the power to run some of the more diabolical designs.  When the trigger is activated, it sends a [[lever|signal]] to the linked device. That signal is not always as simple as "do it now", but it's specifically either to "open" or to "close".  By manipulating what does what and when, and what follows from that, impressive results can be achieved.

:''(* specifically, the [[Trap#Stone-fall_Trap|stone-fall trap]], [[Trap#Weapon_Trap|weapon trap]], and [[Trap#Cage_Trap|cage trap]].)''

These are the simple [[trap]]s that are placed by a mechanic. They require one [[mechanism]] but do not require levers or triggers.  They can be a quick, easy and brutally effective "first defense" for a fledgling fortress, but they can also be combined into key parts of more complex set ups. For tips on using these basic traps effectively, see the Trap Strategies section.

:This is the easiest trap to build, so you can easily build them in large numbers. Building lots of them is an easy way to earn experience for your [[mechanic]], and add to the depth of your fort's defenses at the same time. Surrounding intersections and stairways is a good way of handling threats that make it inside the fortress, including berserk dwarves.

:Using [[crossbow]]s or other projectile weapons in weapon traps avoids the problem of jamming, but they must be kept loaded with [[ammo]].  Mechanics will load them with any ammo that is not forbidden.  They will load each until each type of weapon has ten rounds of ammo.  Hammers seem to jam less than swords or axes, and spears seem to jam the most. Your dwarves will attempt to unjam traps unless otherwise forbidden.

:A very powerful type of trap. Maybe even too powerful - currently, even a wooden or glass [[cage]] can hold indefinitely any creature short of a [[titan]], even trolls and megabeasts. A cage trap never fails, although creatures with the [[creature token|[TRAP_AVOID]]] tag cannot be captured unless knocked unconscious or [[Giant cave spider|webbed]] first. Use cage traps as your outermost traps to catch the occasional wandering animal, angry wounded [[elephant]] or [[unicorn]], or even [[zombie]]s. Caged animals and enemies will be safely brought to any animal stockpiles you have, but may escape later if you are not careful. For more information, see [[captured creatures]].

These traps require a trigger such as a [[pressure plate]] or [[lever]]. They will require at least three [[mechanisms]], one for the trigger and two to create the link. The trigger can be located any distance from the trap, typically close for a pressure plate or far away for a lever.

For a system that repeatedly activates automatically and regularly regardless of enemies, see [[Repeater]].

Menacing [[trap component|spike]]s or upright spears appear on the basic mechanic's {{k|T}}rap menu, but must be activated remotely to pop out of the ground and impale anyone standing on that tile.  Vast forests of these can make any area a killing field.   

While upright spike defense systems never jam, they also do not discriminate. When activated, they will inflict piercing damage on whatever is standing on the tile, whether it be friend or foe.  You can use [[traffic|traffic designations]] to help somewhat.  Designate the spike trap tiles as "restricted" then make a longer path going around the spikes that's designated as "high traffic."  Pets and merchants/diplomats will probably still get skewered, though.

Enemies will hunt down and kill friendly tame animals wandering outside if they have nothing better to do. Put an expendable animal on a [[restraint]] or in a 1x1 pen [[zone]] in some random spot outside, build a few columns around it to reduce the chance of them shooting it, and trap that area to hell and back. Also known as the "Tar Baby" strategy.

Lowering [[drawbridge]]s on invaders will [[dwarven atom smasher|crush]] them into nothingness. Known as the 'Dwarven Atom Smasher', bridges will destroy most things with some notable exceptions including [[wagon]]s and [[elephant]]s, who will not only survive unscathed but also destroy the bridge.

Try replacing the side wall of a part of your main entrance with a drawbridge, big enough so it spans the whole hallway. Link the drawbridge to a [[lever|trigger]], and whenever you feel like it activate the trap.  This can be done with minimal effort and used to smash [[invader]]s, unwanted [[immigrants]], bothersome [[nobles]], or simply to destroy your garbage.

[[Support]]s can be linked to triggers. Building a section of floor that is deliberately held up only by a trapped support allows for an intentional [[cave-in]].

* Cave-ins will ''not'' reveal invisible invaders, such as [[ambush]]ers unless it kills them outright, in which case their bodies become visible.

The biggest drawback of this sort of trap is the "reload" process, which can be relatively time consuming.  Have a drawbridge that can seal off the work area so your [[mechanic]]s and [[mason]]s can reconstruct the setup in peace.

These traps drown, freeze, boil, or wash targets away.  Errors in execution can be quite <s>[[flood|harmful]] to your fortress</s> [[fun]], so use with caution.

NOTE: Traps involving large quantities of water turning into steam are as effective at killing your [[framerate]] as they are [[goblin|goblins]]. Use with caution, and have the cut-off lever at the ready.

   ->++▼··················▼++->  <tt>▼</tt>  - Down-Ramps (as visible from one level above = see [[ramp]])

If enemies are in the middle of Level -1, open the inflow, then the water will first trap, and then drown them. If the pit is full, close the in- and open the outflow. You can automate this by using [[pressure plate]]s, or if you want to have more fun, replace the water with [[magma]] (which would require pressure plates and floodgates to be [[magma-safe]]).

This is a trap that can be built in discrete units. Each unit requires a lot of labor and protects only a small area, though in a dramatic manner. A wall of these around the map sharing a single massive water reservoir makes a very effective [[siege]] defense, as each tower component can be linked to a [[lever]] and used to wipe out a single invading squad at a time. Note: This may count as a [[stupid dwarf trick]].

While a [[pressure plate]] in the center of this trap can trigger it and drown hidden ambushers, such an arrangement is subject to double-activation and failure.  A pressure plate that only triggers once will break and the system will be incapable of self-reloading. A lever is highly recommended.

Using a cross-hair pattern of walls, invaders are herded through the trap. Inside the fortress, Urist McLeverpuller does his job. [[Floodgate]]s on the ground close, [[hatch]]es on the ceiling open, and drowning ensues. When all enemies are dead, the lever is pulled again. The hatches close and the floodgates open, allowing a rush of water and bodies to spill out.  

   ->++++++++++++++++++++++++++·  <tt>▼</tt> - Down-Ramps (as visible from one level above = see [[ramp]])

Be sure that the reservoir can hold enough water to flush everything out (3 levels should be enough), that it can be automatically or easily refilled quickly, and be advised that flushing your own dwarves can be much [[fun]]. Adjust the height of the chasm depending on how much damage you want to cause to intruders or to [[Unfortunate accident|innocent bystanders]] (7 levels start to do some serious damage).

These traps incinerate targets, or possibly encase them in obsidian.  Magma does not play favorites - read up (again) on [[magma]], and use with ''extreme'' caution. Fire traps are included in this category because magma is often the best method of starting a fire.  

Certain minerals such as [[lignite]] and [[graphite]] have an ignition point but no melting point, meaning that once they are set on [[fire]] they will burn for a very long time (about 9-10 months) unless exposed to water or rain. Any item made out of these materials has this property, which can be used to design horrifying fiery death traps.

Consider a hallway filled with lignite [[floor grate]]s, which can be built directly on the floor and do not impede the passage of enemies. Pouring [[magma]] on any one of these grates will set it alight, and the fire will spread to all connected grates. The end result is a lot of constant smoke and a hallway that kills anything that passes through it. Consider [[traffic|restricting access]] to your dwarves or building this in a pit with a retractable bridge over top: the mere fact that a location is on fire will not stop them from walking through it. On the plus side, [[goblin]]s are just as stupid.

Variation: Drop goblins into a holding pit with various spike traps linked to your pressure plate artfully placed around the chamber. Watch as every dining hall [[party]] begins to be measured in goblin blood.

A uselessly complicated collapsing spiral trap can take out ten goblins at a time. When finished, it looks like this:

The goblins are lured in by a [[restraint|restrain]]ed bait animal, and can't shoot it due to the surrounding walls. Just before they reach the bait, they trigger a pressure plate that retracts the bridge and collapses the support holding up the whole spiral.  Goblins, bait animal, walls and all plummet into the chasm.

When building, you will need to [[construction|build]] a span of floor underneath, for the support, as bridges do not support constructions (''which is also why you want a bridge as the access, so it will not hold up the trap*)''. You will also need to have a floor tile between your floor and solid ground or wall while constructing, as the bridge alone will not work as a base, but you can remove it once the support is in place.

Because the outcome of this fairly complex trap can be easily obtained by just using a retractable bridge,  it qualifies as a [[stupid dwarf trick]].

 

 

 

In any suitable open area which hasn't been dug out underneath, build a support and an adjacent multi-use pressure plate set to trigger on creatures (but not citizens), link them together, then build floor tiles above the support and pressure plate. When an enemy steps on the pressure plate, the game will pause and recenter the view with the announcement "''A section of the cavern has collapsed!''", at which point the enemy will be crushed and its companions will be stunned or knocked unconscious by the cloud of dust (though not necessarily revealed, in the case of an [[ambush]]).  

This is an extremely effective and nearly maintenance-free way of defending against invading enemies. The simplest design is a straight corridor with a [[hatch]] on either end, triggered by a [[pressure plate]] immediately before it.  A channel is carved under the hatches and the ramp removed.  The corridor is then filled with traps.   

  #^ ^^^^^^^^^^^^^^^^ ^#

Its two main disadvantages are being susceptible to both trap-avoiding creatures and [[building destroyer|Building Destroyers]]. These can be safeguarded by any of the other many usual ways of defending against this type of creature.  It's also possible for a creature to be "stuck" in only the first few tiles of the trap, as they try to escape after taking enough damage, only walking two or three steps into the trap, then immediately turning around and trying to exit, and so only walking past already-triggered traps.  Again, you can get rid of these with your military with no problem.

* Fill with very weak weapon traps that will only maim the prisoner.  Put an [[dwarven atom smasher|atom smasher]] near the other end that will be triggered as he tries to crawl towards freedom.

 

 

 

 

 

 

 

 

{{category|Fortress defense}}

{{category|Traps|*}}