A fast interactive Sudoku solver written in Javascript. Handles many Sudoku variants including Killer Sudoku and Jigsaw Sudoku.
An infinitly* zoomable Stern-Brocot Tree. This structure contains all positive rational numbers in their lowest form, and in order.
An article showing how to define a simple, efficient enumeration of the rational numbers.
An interactive demo of Reed-Solomon error correction. It also explains the algorithm at a high level assuming knowledge of polynomial arithmetic and solving linear equations.
Collection of logic and math puzzles.