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Wednesday, June 22, 2011

Trap Synthesis

OK, why did I go through all that tedious definition of terms yesterday?

It's because of this: you can sort traps and tricks based on the obviousness/obscurity of its clues, triggers, and payoffs, and to a lesser extent based on its known/unknown status.

We'll use doors as an example. All the details about a door that indicate (1)" something is there;" and (2) "it's a door, so you can do standard 'door' actions to it" count as one clue: size, shape, material, condition (sturdy, aged, rotting,) design of hinges, open/closed status, and so on. All of this counts as one Obvious clue, indicating a trivial, Common knowledge fact (there's a door there, which might have something behind it.) If there is another set of details that is not Obvious or Common, it counts as a second clue.

The door also has an Obvious trigger/payoff pair: "if you push the door, it opens". triggers are always the first part of a conditional (If X,) with the second part (Then Y) being the payoff. If both the trigger and the payoff are Obvious and Common knowledge, we can skip them entirely and treat the dungeon feature as having no trigger/payoff, just as we would an ordinary door.

Here's our possibilities, with "Any" meaning anything but "None":
  • No trigger, No payoff: Dungeon Feature (furniture, found objects, etc.)
  • No trigger, Obvious but unexpected harmful payoff: Hazard
  • No trigger/Any trigger, Obvious but unexpected useful payoff: Resource
  • No trigger/Any trigger, Obvious but unexpected limiting payoff: Obstacle
  • Any Trigger, but No payoff: Decoy
  • Obvious simple trigger, Obvious payoff: Bait (if used in conjunction with another trigger/payoff)
  • Any trigger, Any payoff: Trap
  • Bait or Decoy + Trap: Trick
  • harmful Bait/Decoy + Trap: Perverse Trick
Hazards are harmful payoffs delivered automatically as a result of ordinary actions, such as standing next to or in a door that's on fire, or pushing open a door covered with needles; Hazards are listed as "No trigger", because the actions are too simple to note; the GM applies the harm based on common sense. Obstacles are similar, but instead of being harmful, they merely prevent one or more kinds of action until dealt with. Adding a lock to the door as a trigger would turn the door into an Obstacle. The payoffs for these (and for Resources) are listed as Obvious, because the harm, limit or benefit is either automatic or easily acquired.

One way to turn a door into a Decoy would be to make it a false door: the Obvious trigger is the door itself or possibly its knob, the Private (or Lost) knowledge about it is that there is no payoff -- the door won't open. Adding a lock makes the false door a more convincing Decoy and bigger waste of time. Another method would be to add a false trigger, such as a wire across the door, making it look booby-trapped. This works best if the "trap" is Obvious, but you can have Hidden traps of various kinds as well.

Traps must have both a trigger and a payoff, although Resources, Obstacles and Bait are specifically excluded because of their additional, special rules. We can break the simple ones down further this way:
  • Obvious trigger, Any useful payoff: Device (tool, machine, etc.)
  • Obvious trigger, Obvious payoff: Territory Marker (obvious crossbow trap covering entrance, for example, or obvious security cameras in a modern public plaza.)
  • Any trigger, Any limiting payoff: Obstacle Trap
  • Any trigger, Any harmful payoff: Hazard Trap
  • Any trigger, Any warning as payoff: Alarm
  • Any trigger, Any limit removal as payoff: Access Trigger
  • Uncommon/Private/Lost trigger, Any useful payoff: Test
And of course, you can break down each limiting, harmful, or warning payoff by type, which is where most trap categorizing schemes start.

What makes a Trick different from a trap is the fact that there is always a Bait or Decoy involved that leads characters to expect one thing (implied by the Bait or Decoy,) but get caught by something completely different (the actual Trap.) In other words, attempting to trigger one payoff triggers one or more other payoffs instead. Tricks are the simplest kind of sequential combo (payoff is itself a trigger for another payoff,) which are also the basis of Sequential Combo Traps. Other kinds of complex trap are built around parallel combos (trigger has multiple simultaneous payoffs,) sequential triggers (payoff requires multiple triggers in order,) and parallel triggers (payoff requires multiple simultaneous triggers.)

One way to use all this information for more interesting traps and tricks would be to start not with "what does this trap do in the game?" but with the answers to these questions:
  • "How many triggers and payoffs are there?"
  • "Where are they located?"
  • "How obvious is each trigger or payoff?"
  • "How much knowledge is required to operate each trigger, or recognize each payoff?"
  • "Is there any bait or decoy involved, to encourage operating a trigger?"
You could start with an unkeyed rough sketch-map of your dungeon. In each room, put one or more numbers, to indicate triggers. Connect one number to another with a simple line, to indicate that both triggers must be triggered simultaneously; use an arrow instead to indicate a sequence. Place one or more letters in each room, to indicate payoffs; some of these can be placed at room entrances or tunnel choke points, to indicate possible changes to dungeon access. Connect one or more triggers to the payoffs with arrows. Connect a couple payoffs with arrows to other payoffs, to indicate that the payoff is, itself, a trigger.

This will give you a couple sequences, which may be spread out over several rooms. You can now decide what each kind of payoff is: Treasure? Opened or Sealed passage? Covered pit? Flaming oil? Set the obviousness and knowledge of the payoff, to set its difficulty. Decide what trigger(s) would be interesting or appropriate for that payoff. If a trigger links to multiple payoffs, decide whether all payoffs are activated with a single action or each payoff is activated by a different action on that trigger (multi-position lever, button panel.) Or, alternatively, if a multi-payoff trigger is itself linked to other triggers, the payoff delivered depends on the sequence of triggers.

All of this, of course, skips over questions of realism or purpose entirely. These can come into play after the trigger/payoff map is drawn, during the description phase; but lot of the rationale of a trick or trap can be delayed until after the entire dungeon is keyed, or even occasionally during play.


  1. Enjoying the posts. Loads of material to digest. :)

  2. Very good stuff, but one comment:

    You could go so far as to get rid of the useful/harmful distinction in many cases - it's quite useful to trigger the poison dart trap if there's an ogre standing between you and the launcher - and just leave it at "trigger/payoff". I guess maybe a "dangerous/valuable" distinction might serve better.

  3. @Witness: by "useful", I mean "useful to the target/victim", with the understanding that the action is not harmful. It's true that a dart trap can be used against an ogre instead of against the person who triggers the trap -- but that's the default assumption: if you can come up with a way to use something that was intended to be harmful, then go for it.