IED trap

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IED traps ("improvised explosive device" traps) are artisanal landmines made out of high-explosive shells.

Acquisition

IED traps can be constructed once the Ieds research project has been completed. They require 2 High-explosive shells, 1,400 ticks (23.33 secs) of work, and a Construction skill of 3.

Summary

Traps are single use security buildings that may be triggered when a pawn of any kind walks over it.

The base trigger chance is 100% for enemies, including mechanoids and animals affected by the manhunter mental state. Note that despite the name, animals currently hunting a human pawn for food are not "manhunters" and are not considered enemies.
Non-manhunting wild animals have a 25% chance to trigger the trap.
Colonists and tame animals have 0.4% (one in 250) chance to trigger the trap.^{[Friendly Mechanoids?]}
Friendly visitors and their animals will never trigger a trap.

However, colonists and non-manhunting animals are aware of the location of traps, and will avoid pathing over them if reasonably practical.^{[Path Cost?]} One notable exception is roped animals being dragged by a handler - the rope limits their movement, overriding their usual behavior.

Prisoners are considered to be their original faction for the purposes of traps. Enemy who you have taken prisoner will retain their 100% trap trigger rate and will ignore traps when pathfinding. Colonists that you have taken prisoner retain their 0.4% trap trigger rate, even during a prison break, and will avoid traps whenever possible.

In all instances, the nimble trait multiplies the trigger chance for that pawn by 10%, that is, a 10% chance for enemies and 0.04% chance for friendly pawns.
IEDs can also be triggered when hit by a projectile dealing the Bullet, Arrow, or ArrowHighVelocity damage type, or when damaged below 20% of their maximum HP.

When triggered, the trap will begin to spark and emit a hissing sound for 15 ticks (0.25 secs) before exploding, dealing 50 Bomb damage in a 3.9-tile radius. Bomb damage has additional damage multipliers depending on the target, see Bomb for details.

Non-drafted pawns will attempt to run from an activated IED trap.^[Verify]

Analysis

It is inadvisable to place them in the open, as manhunting animals could trigger them. Colonists, friendlies and sane animals are aware of placed traps and will walk around them, but only if another short route is available. Pawns will not be able to avoid traps placed in a long continuous line, or in choke points like a narrow hallway. A trap is less likely to be triggered by a colonist or friendly (0.4% chance).

Placement requires some forethought by guessing positions where the enemies will be stuck for a couple of seconds such as cover spots (rocks or walls) and choke points on the side where enemies would take cover when engaging your colonists. Example: an IED trap surrounded by a tile or two of sandbags will explode while victims are still close due to the reduced movement speed to walk out over them.

As a detonator

IED traps can be triggered by shooting at them, so they can be placed near other high-explosive shells to make a bigger explosion, to destroy crashed ship parts for example.

Here, a dozen of high-explosive shells are placed near a defoliator ship (1200 HP), along with an IED trap.

It requires a bit of micro-management to place individual stacks of shells (make the shell at a machining table, carry it to a 1×1 stockpile zone, delete this zone to avoid having more shells on it, repeat), and a careful placement of the trap (placing it too close to a mecha will wake it up), but the explosion will destroy the defoliator outright. The pawn shooting at the IED trap should be ready to run very fast, or better: wear a jump pack to avoid being sliced up by the waking mechas.

Unfortunately, a stack of 12 shells doesn't make the same damage as 12 stacks of one, so individual stacks have to be made (in fact, a stack of 25 shells exploding brings the defoliator to 725/1200, not even half the damage for more than twice the amount of shells).

This technique works well to destroy ship parts, or possibly sleeping scythers that accompany it, but killing centipedes would require much more shells and is clearly not the best method: kiting them is much easier.

Roof Fall Trap

Since the IED deals bomb damage, building a large roof supported by a single wooden wall within range of an IED can cause a roof collapse when the IED is triggered, which can deal additional damage in a much larger area for a low additional cost.

Version history

0.11.877 - Added.
1.1.0 - IEDs explode when bullets hit them. This allows the player to purposefully shoot them to set them off.

Architect

Security: Barricade • Sandbags • Spike trap
(research): Autocannon turret • Foam turret • Mini-turret • Rocketswarm launcher • Uranium slug turret • Mortar
IEDs: IED trap • IED incendiary trap • IED EMP trap • IED firefoam trap • IED smoke trap • IED antigrain warhead trap • IED tox trap
Related: Antigrain warhead • EMP shell • Firefoam shell • High-explosive shell • Incendiary shell • Smoke shell • Tox shell