The puzzle is a plain, wooden box with the letters of the alphabet painted on top along with four lights. The box is locked and there are no visible buttons or switches.
So how do you get in?
While trying to find some hidden switch, you notice that touching some of the letters turn on the lights. After trying all of the letters, you find that N, P, O, E control the lights, and trying them in different orders shows that each letter controls a different light. While most combinations just make the lights turn on momentarily, trying O-P-E-N causes the lights to blink and the box to unlock.
Check out the video below: