The Chinese Remainder Clock

A mathematical clock based on the Chinese Remainder Theorem.
Sliding mask

Visualizing recurrence sequences

A sliding mask to visualize the recurrence relation for the Fibonacci sequence and any other recurrence sequence.
  • Unmasking recurrence sequences, pdf, to appear in Pi in the Sky (Issue 21, 2018).
This original idea (of 2014) was appreciated by the mathematikum because they changed accordingly the exhibit about the Fibonacci numbers.
Master Mind Rad

The Mastermind Wheel

A didactical tool for understanding Knuth's algorithm for winning Mastermind in at most five moves.
  • The Master Mind Wheel (originally Mastermind Rad in Alexander Lang's Diploma Thesis) and some introductory Slides.
  • with Thomas M. Fiore and Alexander Lang, Tactile tools for teaching: an implementation of Knuth's algorithm for mastering mastermind, to appear in The College Mathematics Journal (planned for the September puzzles and games issue, 2018).


A didactical card game for learning the Congruence and Similarity Theorems for triangles.
  • Sim!Cong!, The instructions and the set of printable cards (free for personal use, or use in class for instructors).
  • Leaflet, Guidelines for commercial use (University of Luxembourg).

5-Con triangles

Triangles that are almost congruent.
  • Creation of the Wikipedia page 5-Con triangles (user: Antonellaper).
  • The article Driehoeken met onderling 5 gelijke zijden en hoeken, translated and edited by Luc Van den Broeck, to appear in the Dutch/Flemish magazine Uitwiskeling. Here the English version.
Arithmetic billiard

Arithmetic billiards

A geometric construction for the gcd and the lcm.
  • Creation of the Wikipedia page Arithmetic billiards (user: Antonellaper)
  • The article Arithmetic billiards pdf (submitted version), to appear in Plus Magazine edited by Marianne Freiberger.

Math around the Clock

Various original mathematical clocks.

PytEuk Puzzle

A mathematical exhibit around Pythagoras' Theorem.
  • PytEuk, a puzzle that shows Pythagoras' Theorem and the classical decomposition of the square on the hypothenuse.

Further mathematical exhibits

Drehoskop (to explore solids).
GoFlex (composable flexible stripes).
  • with Edith Wittman, Drehoskop, a tool to detect rotational symmetries for polyhedra (these can rotate on various axes).
  • GoFlex, reconfigurable flexible stripes to create Möbius bands and other geometrical objects.

Further mathematical projects

A Wikipedia Page about the most difficult logical riddle.
Mockingjay Mathematics (movie-inspired problems).