In case you haven't guessed already, we have some Sudoku fans here at Microsoft. It's challenging, stimulating, and just plain fun. Stephen Toub, the ".NET Matters" columnist for MSDN, has created a fantastic implementation of Sudoku in C# for the Touch Pack software bundle shipping with Ultra-Mobile PCs, like Tablets. As you can see in his MSDN article "Microsoft Sudoku: Optimizing UMPC Applications for Touch and Ink", this is a wonderfully complete implementation of the game. And, in the Coding4Fun spirit, Stephen shares his source code, offers a great narrative on the implementation, and offers ideas on how to extend the application. (I especially like the fact he left open the possibility of moving the UI to Media Center Markup Language in Vista and using the remote control to play the game!) Thank you Stephen, for such a great example of Coding4Fun and for helping those of us 'jonesing" for more opportunities to combine our love of Sudoku with interesting coding challenges.