For the Ninth Gathering For Gardner I designed an appropriate exchange gift.
It consists of 9 pieces, 3 different kind of pieces (all square), 3 copies
of each kind. Additionally, it had to be cheap to produce (as 300 copies
were required). Therefore, all pieces had to be planar and producable on
my lasercutting machine in a reasonable amount of time. After a much
thinking I decided that the puzzle whould look like this.

The puzzle is based on a 11x11x11 grid. Each piece is based on a 11x11
grid. I tested many shapes, but eventually settled on the following
set:

This set has a couple of very nice properties:

- There is only one solution
- The puzzle does not fall apart too easily (it is a level 3 puzzle meaning that the first piece comes out on the third move)

Download BurrTools for
your operating system and download the puzzle
definition file. Open the file with BurrTools, select the tab
**Solver** and drag the slider under **Move** to see how the
puzzle is taken apart and put back together again. Rotate the view
by dragging in the image on the right.

The log files of this web
server are stored for a loooong time, so you may want to think twice
before you download the solution. Solving it yourself is so much nicer.

Peter Knoppers