Editing 40d:Trap design

* See the [[Defense guide]] for a general overview of threats and considerations for fortress defense.

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]]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 [[Trigger#On.2FOff_vs_Open.2FClose|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.

Another options for outside defenses is scattered traps.  Most hostile forces will flee if they take enough casualties, and stone-fall traps can be quite damaging to goblins and are easy to set up.  Cage traps work even on [[Bronze colossus]]es and [[Dragon]]s.  You just have to make sure your dwarves working outside actually stay near your traps - a fisherdwarf who goes wandering screens away from the nearest trap is not protected.  A wall of traps is a passive threat to injure, kill or capture enemies who will happily walk right into them.  (This can work so well that some players decline to use it, and prefer a more complex challenge.)

   ║  ║xx    ??

   ║  ║x    ???  

   ║???║  .????    ? = unpredictable path  

   ║ ??║ . ║        . = ''most likely'' path

   ║x  . x║

   ║xx  xx║         x = ''unlikely'' detour  

: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.

These traps require a trigger such as a [[pressure plate]] or [[lever]] pull. They will require at least three [[mechanism]]s, 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.

 

You can also 'Arm' a defense system that involves pressure plates by pulling levers 'Activating' said pressure plates. The process is also fairly simple and cheap. First, you need a lever that will activate the system, after that you need to channel out a section to put your pressure plates, this can be anywhere you would normally put a pressure plate, and be at least three blocks long (one for the pressure plate, two for ramps). Add the pressure plate in the middle of this channel and ramps on the far sides. Over this gap make a drawbridge that either retracts or raises to the left or right, and connect it to the lever made earlier. Connect the pressure plates to you Fun Creating System of choice, and voila, you have a working switch.

Try replacing the side wall of a part of your main entranceway with a drawbridge, big enough so it spans the whole hallway.  To prevent enemies from wrecking it, you could dig a channel in front of it so its protected while its raised.  Link the drawbridge up to a pressure plate or lever, whatever you prefer.  Whenever you feel like it, activate the trap, and watch the drawbridge fall directly into the hall, utterly squashing nearly anything beneath it.  This can be done with minimal effort and used to smash invaders, unwanted immigrants, nobles, or simply to destroy your garbage.  This is based on the 'Dwarven Atom Smasher' device mentioned elsewhere in the wiki.

 

Note that sufficiently large creatures (those with a [[Creature token#S|SIZE]] greater than 10) cannot be crushed - attempting to do so will instead merely destroy the drawbridge itself.

* Dropping a floor directly onto any creature will ''instantly'' kill it, regardless of its size.

     ░░▲++▼··▼++++++▼··▼++▲░░  

     ░░░░░░XX░░░░░░░░XX░░░░░░   <tt>▼</tt> - Down-Ramps

Create an airlock using two bridges, two doors or whatever.  Make it a medium-sized chamber, perhaps 10x10 or so.  Channel out the floors around the rim, and rig up a system to pump magma into the room, or drop it from the roof.  Enemies will quickly be destroyed, and with the magma in the channels, you can pump it out for future use or just leave it.  The idea here is a re-usable magma trap; you can use this with a pressure plate, too.  It also leaves behind any magma-proof items the invaders might have been carrying.

:''(* A set of floor [[bars]] or [[grate]] would work as well, but the bridge can aid in the (re-)construction of the trap.)''

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]]). As added bonuses, by using a multi-use pressure plate, the collapsing floor will deconstruct the plate and usually leave its mechanisms lying on the ground for reuse, along with other building materials used (the materials used to construct the support and floor tiles, plus the mechanism used in the support) - alternatively, if a single-use pressure plate is used, both of its mechanisms (but not the one used in the support) will be destroyed, making this one way to dispose of low-quality mechanisms created by unskilled [[engineer]]s (aside from selling them to caravans, dumping them in [[magma]], or crushing them under a [[Dwarven Atom Smasher|drawbridge]]).

''(Note - [[Trader]]s will NOT stop at your fortress unless there is a clear, 3-wide path to a [[Trade depot]] when they arrive.  Bridge 2 should be kept down if you want/expect Traders.)''

===Pitfall Trap===

A simpler type of Bridge Landmine, related to the above Chasm Trap. Construct a number of retracting bridges over a pit, leaving one empty square over which you should construct a floor tile. Put a pressure plate on said tile, and link it to all the bridges. What you do with the pit is limited only by your imagination and your interest in recovering enemy weapons, armour and cave spider silk underwear.

Variation A: A long retracting bridge in the entrance tunnel, with the pressure plate right in front of the fortress doors. The expression on the face of the point-goblin who reaches them only to watch his comrades plunge to whatever gruesome fate you have prepared for them will be a mental picture to cherish.

Variation B: Much as above, but outside and with a raising bridge.

Basically you heat a corridor from below with magma. You can then flood this corridor with water without the water freezing (because of the magma). Then if you remove the magma from the room below the water will freeze killing anything in it. Refilling the room below with magma melts the ice allowing pumps to drain the room.

{{Category|Guides}}

{{Category|Fortress defense}}

{{Category|Design}}