About Sudoku Challenge
Sudoku Challenge lets you play freshly generated Sudokus straight in your browser. Whenever you solve a Sudoku you will get the option to challenge a friend to beat your time.
The site is a hobby project made by Mathias Biilmann Christensen in Ruby on Rails. The heart of the application is a homemade Sudoku solver based on Donald Knuth's DLX algorithm, turned into a lightning fast Sudoku generator.