No label defined (Q59109)

After giving kids another pile of 20mm calibration boxes and seeing complete lack of interest in the eyes, it struck me that the boxes can be used as tiles for a puzzle game I saw a long time ago. The only thing it needs is a box and 15 tiles with numbers. The tiles are mixed at the start and the goal is to arrange them in order by sliding into the only free spot available (without taking out of the box). P.S. If you want to make a nice print of this puzzle rather than find a way to reuse a pile of the calibration boxes take a look at the thing already available on the Thingiverse: http://www.thingiverse.com/thing:15377