Jaap's Scratch Pad


This is the place where I dump stuff that is not (or not yet) part of my puzzle page (Jaap's Puzzle Page).

Downloadable version of my puzzle page, excluding the patent pdfs and large gallery images: puzzles.zip (34.7 MB)
The puzzle patents: patents.zip (85.8 MB)
The gallery: gallery.zip (567 MB)

Here are some javascript puzzle scramblers:
   Rubik's Cube Scrambler for any size cube.
   Megaminx Scrambler.
   Square-1 Scrambler
   Rubik's Clock Scrambler
   Rubik's Clock Scrambler, graphical version
   Rubik's Ufo Scrambler.
   Download all scamblers.

Sudoku generator. Fast generator/solver for various sudoku variants. A Java applet.


Tilings page. It has a Java applet with a catalogue of hundreds of tilings that I found which each use only one polygonal tile shape.

Psion Organiser Series II

Psion Organiser Series II page. It has pictures of my collection of Psion II gear, as well as lots of technical documents, software, ROM and software pack image files, as well as a section on its predecessor, the Psion Organiser Series 1.

Mechanical Calculators

Mechanical Calculators page. A few pages about the mechanical calculation machines that I own, in particular a Curta and a Comptometer.


The DIY-Gamer page has software that I've written for this geeky toy based on an Arduino.


My YouTube channel. Some videos of mine, mostly magic tricks.


Here (600K wav file) is a voicemail message someone left on my mobile phone some time in 2002. It is in a kind of German, and rather funny.

I have an old nokia phone (6021), and have written programs for it. To install a program on a Nokia you need the PC Suite software.
Twister.jar, Twister.jad, Source Code. Puzzle game, like a 2d version of the Rubik's Cube.