Electronic interactivity?

Question

Do it yourself

I was in the quest room yesterday (this is the place where you have to solve puzzles to get out of the room). One of the puzzles was this:
You need to hang the portraits in a certain order, after which an event occurs.
My question is how can this be implemented? In iron, I am an absolute zero, I skipped physics lessons. Therefore, I could not google anything (I just don’t know how to formulate the question correctly). I understand that each picture should have a certain sign and when these signs are in the right order -> we generate an event. But I couldn't think of a sign that it could be.
The portraits were 25cm x 40cm. Plain wood frame and glass. A loop of some kind of wire, the nail was metal too. The nails were not in the wall, but in the board. The board was already attached to the wall. There was nothing on the board but nails.

Answer 1

As an option - within the framework of the pictures - rfid tags (such as in stores they mold books, for example). In the wall are receivers with a small reading radius.

Answer 2

You can also use reed switches. Each picture has its own corner. Connect in series. If everyone hangs correctly, then the magnets will close the circuit.

Answer 3

I guess a few hidden cameras solve most of the cases in the room.
The rfid tags that Vladimir mentioned were the first thing that came to mind, but messing around for the sake of one trick, picking and patching up the walls, is unlikely. Moreover, visual control is needed in any way - suddenly someone has an attack of claustrophobia.

Answer 4

I did something similar for a quest. used reed switches - simple, cheap, no controller needed for implementation.
The only negative is that you need a fairly accurate positioning of the magnet-reed switch.
Video surveillance for this is used only by very simple quest rooms. It is easy to automate - and it’s hard to follow with your eyes.