This project uses 5 (arbitrary) magnetic reed switches in series with a battery and come LEDs. They are embedded in foam-core board, with the map overlaid on top. Some tokens have embedded rare earth magnets, so that when the tokens are placed in the correct location, on top of the switches, the switches are all turned on, which completes the circuit and illuminates some LEDs. The LEDs light up certain parts of the key of the map, which reveals the solution to the puzzle.