It takes 7 moves to open, but after the first few successful moves, it becomes apparent how to solve. (For better or worse - but this is a fine intro into puzzle boxes.)

Created from wisps of internet vapor, based on a youtube video that mentioned this kind of puzzle. The person in the video had made a version from Bruce Vinley (homemadepuzzles.co.uk), but the plans on his site were...meant for wood, not in a CAD version, and it wasn't really clear how it worked or the sizing. If you're interested in learning how to create a puzzle in a CAD program, might check out the "Free Plans" on his site.

Assembly can be done after gluing, but you might play with it pre-glue so you can see how the pieces move. (Right and left are the same piece, I left them labeled for clarity.) The 'longer' tail of the Bottom panel is the part sticking out as you insert the panels.

The "inner box" is 40mm x 20mm x 15mm. The exterior is 80mm x 40mm x 50mm.