dan mackinnon

Recreational mathematics and puzzles


Logic puzzles inspired by those of Raymond M. Smullyan.

Portia's Caskets | Can you find Portia's portrait? Adapted from puzzles found in What is the Name of this Book?.

Knights and Knaves | Who is a knight and who is a knave? Adapted from puzzles by Raymond M. Smullyan, particularly those found in What is the Name of this Book?.

The Forest of Forgetfulness | With liars like the Lion and the Unicorn, how can Alice know what day it is? Inspired by puzzles from What is the Name of this Book?.

Tiger or Treasure? | Choose between two doors which may lead to treasure, or something less pleasant. Adapted from puzzles in Smullyan's The Lady or the Tiger?.

Knot Editor | Create or randomly generate celtic knot patterns using the grid method.

PolyGrid | A polynomial grid division calculator and example generator.

Mathematical Chess Puzzles | Attempt solutions to classic chess problems like the 8 queens puzzle.

Chess Tour Puzzles | Try chessboard path puzzles, including Kixote, Hidato, and Numbrix.

Chladni Figures | A page for playing around with chladni-esque figures.

Chladni in Desmos | A Desmos graph for playing around with chladni-esque figures.

Truchet Tiles | Explore patterns and puzzles that are made up of Truchet tiles.

Truchet Book | A pamphlet of all 4x4 patterns with four-fold rotational symmetry.

Sudoku Puzzles | Interactive and downloadable Sudoku puzzles.

Ford Circles and Farey Sequences | Page for displaying Ford circles and their corresponding Farey sequences.

Desmos Interference Patterns | Imagine k points around a circle, each generating a wave (in phase). These waves collide with each other and form an interference pattern within the circle.

The "Brain Fractal" in Desmos | After a certain point, this starts to to look like a brain, and seems to be a fractal.

Drawing Polygonal Numbers in Desmos | Instructions for drawing polygonal number diagrams in Desmos.