Secrets

New feature: trigger (trap) with Perception check, that can activate random secret furniture in visibility of user. Examining this secret furniture depending on Perception can open hidden walls.

As in medieval castles - retractable secret walls.

Description: the player walks around the house, and suddenly he notices that one of the statues (pots or pictures) looks strange. He's trying to do something with suspicious statue when he hears a rattling sound - it opened a hidden wall.

Look on shema:

![map_example](https://cloud.githubusercontent.com/assets/6351438/3444684/56d67f00-0130-11e4-9489-d5c04e7c97c6.png)

On bad perception+intellect you don't detect strange statue (painting, plant...), and can't activate examine it, and have small chances on read a riddle and open the walls. If you failed on examining, 1/10 chances that something bad happens.

Everything is done so that the user does not know what kind of statues with a secret, and what kind of walls open (if more than one)

Also trigger can be useful for many other things: easy to cast one furniture (with specific flag) to other.

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This feature slightly increases usefulness of perception stat.
Stepping on it, trigger disappears (with some chance) and depending on Per+Int/2 can cast special furniture in visibility of user.