[Markus] built his own reverse geocache puzzle box but on a smaller scale than the original. His is based around a PIC 18F2520 and powered by two AAA batteries. The user interface includes one button, a 16×2 character LCD, and a piezo speaker. The box unlocks itself when the GPS module inside detects the proper location on the globe. There is also a secret code that can be tapped on the button to unlock the box prematurely, and another to show the locations in which the user attempted to open the box. This build doesn’t leave much room for a payload, but [Markus] did a great job designing the board and making the components fit as efficiently as possible.