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My interest in logic puzzles dates back to 2003 when I came across a Dutch puzzle magazine called Breinbrekers. I was a fan of all the different logically solvable puzzles immediately. I submitted a few of my hand written puzzles to the editor (Hns Eendebak) and to my suprise they were nice enough to be published and that turned out to be the start of a hobby that has run out of hand.

Breinbrekers, Sudoku Mix and Dutch Sudoku Championships
One of the puzzle types I submitted regularly for Breinbrekers was a chaos sudoku. By then the sudoku wasn’t even invented and the name of the type originally was ‘number place’. When the sudoku became popular, Hns asked me to write variants for a magazine called Sudoku Mix. I also became involved in the Dutch Sudoku Championships. They were held online with sudoku variants from me and Hns. Things went on like this for a couple of years, until the editing house had developed a computer program that spitted out the sudoku variants I made by hand until then. The popularity of sudoku had a negative side effect on the sales numbers of Breinbrekers, so unfortunately that magazine stopped in 2013.

Puzzle Portal of LM Germany
Somehow I stumbled over the website of LM Germany around the time that this puzzle portal saw the light of day in november 2008. The puzzles and sudokus that I wrote for the magazines had to have a limitation on difficulty and may not be too innovative. So the ones that were too hard or too unusual ended up here in the portal. I am not a great inventor of puzzle types, but some of my inventions are Filled Loop, Pentomino in the Box, Blackout Domino and Killer Skyscrapers. I enjoyed publishing puzzles in the portal and the way the portal developed into a playground for experimenting with puzzle types. Together with my puzzle friend Arvid Baars (Eisbär), I have written two nice advent calenders consisting of sudoku variants in 2012 and 2014. The first contained all kind of variants that were not published earlier in the portal and the second contained 24 variants that were combined with each other, with every day of the advent period another combination.

German Sudoku Championships
Around the same time that the puzzle portal was launched, I became involved in the German Sudoku Championships. In the first years, the coordination was done by Stefan Heine and my role was to submit a pile of nice variants that were suitable for a championship. Later I took over the coordination from Stefan. Since the German Championships were always a live event, I visited those championships, meeting my German puzzle friends on a regular once-a-year-basis. (I am Dutch and live in The Netherlands myself.)

When Breinbrekers was taken off the market, Hns wanted to proceed with logic puzzles so we erected the Dutch puzzle Association WCPN (World Class Puzzles from the Netherlands) and launched our own website in 2014. You can find a fresh logic puzzle every weekday. The puzzles are published in a coordinated way, with a mixture of puzzles and sudoku variants with different difficulties and from different authors. Ever since we started, I am board member of the association. With the help of Ortec we were able to organise a live event for the Dutch puzzle and sudoku championships combined on one day since 2017.

World Championship(s)
I have contributed some puzzles and sudokus for a few WPC’s and WSC’s, with a larger share of sudokus for the WSCs in London (2014) and Sofia (2015). When Germany offered to organise the WSC/WPC in 2019, it was more or less natural that I would help them by coordinating the WSC-part and write a huge pile of sudoku variants for it. That was a challenge on itself, since I had no experience in writing team rounds for example. But it turned out well in the end with a succesfull championship. One of the rounds was based on the advent calender 2014 and another round contained 7x7 chaos sudokus, which is a favorite of me and inspiration of LMI’s test 7x7.
I also participated a few times in WPC's and WSC's, in Dutch B and C teams. But I am glad I am normally on the other side of the table; constructing is more my thing than fast solving. :-)

Sudoku Variants Series
Apart from the Dutch and German Sudoku Championships and WSC, I have also contributed to Grand Prix’ held by the WPF and in puzzle and sudoku tests held by LMI and sometimes for other countries National Championships. Since I am involved in so many different competitions and platforms, I am always on the hunt for new ideas for sudoku variants. At a certain moment in 2013, I decided to make a list of sudoku variants that I had not made myself to see if there were interesting types that I could use in one or else championship or competition. The main sources for that were up till then older World Championships, the tests at LMI and the WPF Grand Prix that had just started in the first half of 2013. To my surprise that list was already pretty long. To challenge myself, I decided to try to make my own hand crafted version of every variant that was on that list. That was the birth of SVS. Of course I also included the types that I already had expierence with. The list with possible variants has grown with every new type that was introduced after I started with the series and currently (July 2020) the portal is a good inspiration source for new innovations as well. Criteria for a variant to come on the list are only that I like the variant myself and that it has to have a single ruleset; I don't use combinations of multiple rules. I still like the challenge of writing something ‘new for me’ every time and it is very helpful to have some kind of list when I start writing for a championship or competition.
At the moment SVS contains nearly 300 variants. When someone had told me that when I started with it, I would have declared him/her for mad!
By investigating the possibilities a variant has to offer and an effort to apply this in a puzzle, I hope to contribute in the development of Sudoku, that plays such an important role in my life.

In daily life I am manager of the finance department of the Social and Economic Council of The Netherlands, married and father of two sons (1999 and 2002). My other hobby is listening to progressive rock music (Haken, Dream Theater, Anubis, Riverside, Day Six and Transatlantic are among my favorites) and visiting concerts of these bands together with my brother.