All of these traps are predicated on the idea of Agency.
What's that mean, functionally in play?
When players have their characters walk into the room, they get a description of all relevant manipulable widgets. This way if they miss something, it is due to player choice/skill and not due to a die roll.
This is a very engaging way of playing. Sometimes the experience is so horrible that people will think that other people should not be allowed to play this way! Why is that? Because if this is done poorly it isn't fair. After all, you just killed your players with no warning! Who would want to play in that game?
Here is the problem I ran into when I started. I would describe the room, with all its relevant features. Then my players would avoid the rooms with burn marks, stains, pulverized dust - or only approach them in hazmat suits; and immediately start manipulating every object listed in the room. I didn't want to be unfair. I didn't want to leave anything out. Therefore, at first, everything was simple.
What was the solution? Complex mechanisms and Red Herrings.
When an encounter is designed, you need to leave some clues for traps and such. Do these clues need to be obvious? No. Do these mechanisms need to be simple? No. Does everything you put in the room have to be relevant? No.
Remember, their interactions in the room take time. During this time you're rolling encounter checks. This is the cost of being thorough. Make sure that some of your encounters can threaten your players, so this is an actual cost.
Some actual rules clarifications are useful. I allow people, when unsure of the environment to perform a thorough search. One person can search a 10' x 10' surface section per turn. When they search they get standard chances to detect secret doors. Knowing that the door exists does not automatically mean they know how to open it. I do not inform them of the results of the rolls. This turns the decision into an interesting choice.
Read Part II here. . .
originally published 6/2012