How It Works: https://youtu.be/9t4GRjx8-y8
Build Instructions: https://www.instructables.com/id/Nail-Puzzle-Box/
The goal is to open the box. There isn't any secret panels or buttons to push. Watching the video is the easiest way to see how it works.
Technical
The version shown is made from wood but all files are included to 3D print the box.