My name is Donald Osselaer and I’m from Belgium (the Northern Flemish part specifically). I started to design puzzles when I was about 20 years old and traveling. Being young and very restless (and fed up with the monotony of modern society) I left everything behind, packed my backpack and started hitchhiking across Europe. My first destination was France with a good friend of mine, and later I travelled to Spain and Morocco also.
As I travelled, all of my cooking was done on a little Coleman stove and at night I slept in my trusty tent. For several years, this is how I lived and what a great time it was. At some stage, I found myself settling for a year or so in a very remote village in the Sierra Nevada Mountains in Spain with a girl who was to become the mother of my children and whom I now call my wife, but that’s another story.
Classical and Modern
Puzzles – Classical and Modern – Jack Botermans & J.Slocum
So what has my early traveling to do with my puzzle designing? How did I find this mysterious world of puzzles? With a book by Jerry Slocum, of course! (co-authored by Jack Botermans). This is the book.

The village in Sierra Nevada Mountains in which I lived was literally a collection of ruins. There was no genuine road to the village; it had neither electricity nor the graceful amenities of a modern society. Water came from a natural well and my only power came from a small solar panel that provided us with a means to power an old car radio for music. I lived in a place with no telephone, cell phone, no computer or the internet. As I said earlier, it was actually a great time. Here’s a picture to get an idea.
But enough about the time and the place and onto what you will no doubt be most interested in, the design of my mechanical puzzles.
While reading the aforementioned book, I became especially intrigued by the wooden burr puzzles it introduced and talked about. Fascinated by their design, I chose to try and make some of them and so my first puzzles were a Boule Enfermée and Vernon Wood Puzzle along with some simple 6-piece burrs.
These were all made using very basic hand tools and many bits of wooden pegs I found by the riverbed. Here is a picture of my very humble woodworking shop at the time.
If you look carefully, you will notice a candle in the beer bottle. As I stated, there was no electricity. Also in the picture is a book, where I had drawn up some possible more complex burr pieces.
Little did I know, at the time that someone named Bill Cutler had already analysed all of these burrs. Using only paper and pencil, I decided to try and step it up a notch. Here’s another page from that book.
In the image above, I present my very early design stages of a puzzle I later called Ferrum. For this puzzle, I took the basic concept of a regular 6-piece burr and made it more complex, arriving eventually with a level 26 puzzle.
This may not seem like a lot in these days of computer designed puzzles, however at the time, for me, with only pen and paper and a few bits of wood it felt like a great achievement. I made quite a few of these puzzles.
Once a month I took the bus to Granada, the nearest city, to do some e-mailing and such things in a cyber-café. This is how I somehow came in contact with Frans De Vreugd from The Netherlands.
Frans was kind enough to send me a letter with a bunch of his designs and this later proved to be a major contribution to my own designs. One puzzle, in particular, stood out, namely: Torture.
This is a version of it I made in olive wood and it’s actually quite nice compared to the first puzzles I made. The pieces:
A high-level 9-piece separated board burr
I was immediately attracted by this design as the separated boards lent themselves to high levels but also restrict unwanted movements. My mission was clear: make a high-level 9-piece separated board burr. So I took my book and started drawing.
Below is a page of my book with the first design ideas of what later became Xenon and several similar pages follow it.
Notice the “ideal combination of moves” I came up with. It goes like this: 1-2-1-3-1-2-1-4-1-2-1-3-1-2-1-5- etcetera. This is derived from the famous puzzle with disks called The Tower of Hanoi. It is the maximum number of moves one could possibly enforce with a set number of pieces.
In a certain framework of a certain specific puzzle, however, this ideal combination isn’t always feasible, obviously, but it was my intention to try and find a way to enforce as many moves of this as I possibly could.
After some arduous thinking, sleeping over the complexities of the puzzle and even more pondering, the puzzle gradually formed in my head.
I started giving the pieces certain numbers and names to be able to always see them in their same places while visualising them. Certain pieces also had certain “jobs” to do in the puzzle and so I called one “maze piece” and others “lock piece” and so on.
After a long time of trial and error, refining, visualising, drawing and careful thinking I finally came to a level 50. Note that at this point, I hadn’t used a computer in the design process, I simply didn’t have one. I did however now have a problem.
I had a level 50 design, but I had no way of checking whether it actually worked or not because the design was too complex for me, as a beginner, to manufacture myself. As I’m only human it was also impossible for me to think of all the possible moves and even possible rotations it could have. I was fairly certain that the “right” sequence of moves would work and I had thought a lot and had made certain design choices to try and restrict unwanted movements, but I knew computer analysis was needed.
The next time I went to Granada I came across a program called Puzzle solver 3D and so I was able to verify that my puzzle was indeed of level 50. This was a great personal accomplishment, but I still had no way of making it myself so it remained purely a theoretical design.
Leaving the puzzle, I then started to experiment with a 12 piece variation and I came up with a level 200+ design, but sadly Puzzle Solver 3D wasn’t able to analyse it because it couldn’t handle the sheer amount of possible states and the volume of false moves. Partly because of this limitation in the software, the fact that I had no way of producing them and more importantly because I had decided to travel to Africa about then, my puzzle designing days ended there and then… I forgot about them almost completely.
The story of my enthusiasm for puzzle design, however, was renewed 10 years later, when I stumbled across a program called Burr Tools. Using this fabulous software, I dug up my old puzzle design book and got inspired again.
I got in touch with Maurice Vigouroux, one of the finest puzzle craftsmen in the world, who saw it as a challenge to build my puzzles. He made a number of very beautiful copies which he sold on his website. I received copies of each as a reward. After all those years, I was so happy to be able to actually hold the real thing in my hands.
Notice how each piece is made out of several different pegs to ensure the wood grain runs in the right direction to provide rigidity. They are truly astonishing wood crafted gems.
With Burr Tools, in contrast to the late Puzzle solver 3D, I was now able to analyse my 12-piece design and so Ultraburr came to life.
Now that I had software to help me envision these complex puzzles, I decided to step it up a few notches again. By changing the design of Xenon somewhat and adding voxels, I came to a design I called “Tantalum”. It turned out to be a very difficult puzzle of level 73. This was as high as I could get with that design framework.
Then, I decided to pick up my pencil and my book again and I started to design a new 9-piece board burr from scratch. This time, using everything I had learned from Xenon and Ultraburr, I wanted it to be something really special. For days and nights, I conceived and imagined a new more complex 9-piece board burr until I saw pieces flashing in front of my eyes even when not thinking about them. One evening I was testing out my latest idea in Burr Tools and my “Eureka” cry almost woke up my children. I had found the puzzle I was searching for, my level 100+ 9-piece burr. I named it Fermium. Maurice Vigouroux also made this puzzle.
One Hundred moves may sound like an awful lot, but like the earlier Xenon and in contrast to most other high-level designs, this puzzle is completely human-made. This means that all of the moves in the sequence are specifically intended and thought out by me, a human, and this makes for logic, intuitive moves in logically repeating sequences. This by no means implies that it is easy, but it’s definitely doable even without the solution or help from a computer.
After Fermium, which I still consider to be my masterpiece, I added quite a few more designs to my family of separated board burrs, but for now I’ll let the story rest here.
Sadly, though, only a very limited number of copies were ever made of these puzzles, so I haven’t heard many reviews of them. If anyone reading this does own one I would enjoy hearing your thoughts about the puzzles.
~ Donald Osselaer