This, ladies and gentlemen, is a direction detector. The device has a small hallway, where there are 2 pressure plates. In the center, you can notice 2 redstone torches, next to each other, and a button. When you walk through the hallway, the device will save the direction you went to, and displaying on the torches, turning on the one in the side where you walked to. The button is to reset it. That's it. Enjoy it!