This site is a repository for interesting mathematical diversions. I'll add a new item each month (or so)—something more involved than a simple puzzle. There are now fourteen topics in this site and they are very diverse. I try to choose "real" problems from everyday life. Contributions are welcome (both new problems and solutions to problems that I post).

Sudoku

I noticed recently that sudoku puzzles are becoming quite popular. If you are not familiar with sudoku, then check out the Daily Telegraph Sudoku site. This will introduce you to the puzzle and provide a number of back puzzles for you to work. I'd done some sudoku puzzles before, but I'd only seen them as a novelty. More recently, I've begun playing around to see what makes sudoku work.

It was fun to learn how to solve sudoku puzzles well. There's enough subtlety in the methods that it isn't just a mechanical process. On the other hand, there are just a handful of basic techniques that are used to solve any puzzle. Think about how you solve sudoku, and consider the following:

• What are the techniques that you use to solve sudoku?
• What makes a sudoku puzzle hard or easy?
• Can you design a sudoku puzzle?

I've started creating an online sudoku solver. I'd like to collaborate with anyone who is interested. You don't have to be a programmer; I'm interested in talking with skilled puzzle solvers, too. I'm especially interested in talking with puzzle designers. When I'm done, I want to have an online solver that shows how a human would solve the puzzle. I also want to use the solver to create some sudoku puzzles, which I will post (without use restriction).

If you solve puzzles, I'd like to see some of your solutions (step-by-step). If you have any techniques that you've discovered, I'd like to hear about them. If you design sudoku puzzles, I'd like to know how you approach it.

I have a basic solver coded, and I've been using it to generate puzzles. I've posted several original word sudoku. These are superficially similar to other letter-based sudoku, such as Godoku, Wordoku, or Sudoku Word. But I hope I've provided an interesting twist.

I've noticed that this page has already gotten quite a bit of traffic. From the queries that I've seen, many may be interested in the techniques at Sad Man Software. Others might be interested in the Sudoku Solver by Logic. Of course, working it out for yourself is fun, too.