One of my favorite puzzles is called “pentaminoes.” A pentamino is a shape made by joining five squares together along their edges. There are twelve distinct ways to do this, not counting reflections and rotations. A complete set has one of each.

Since there are twelve pieces in a set, each with an area of five, the area of the whole set is 60 squares. So it’s no surprise that the most common pentamino puzzle is a 6 x 10 rectangle.

Here’s one I designed for the GF. I’m more than pleased with how it came out.

Top of the case for the puzzle.

Pentaminoes puzzle with the top removed showing the puzzle in its 6x10 frame

How the hinge unlatches the top. The bottom layer is the back of the case. The middle is the puzzle frame. And then there’s the top with the hinge.

The back of the case.

You’d be surprised how hard it is to put all twelve pieces into the 6 x 10 frame. It’s all the more surprising when you know there are 2,349 distinct ways to do it.