Designing Sudoku Game

Do you play Sudoku game? I recently got this on web and addicted to it. The game is fairly simple and its numbers and applying your brain game.

(from WebSudoku.com)

The rules are simple. As you see in the picture, this Sudoku is 9 X 9 matrix.
1. Each row and each column of matrix must be filled with 1 to 9 digits.
2. Each small matrix ( 3 X 3) must also have 1 to 9 digits.
3. You cannot change already filled in digits.

So, in the picture, you start filling the missing digits and also make sure you dont break any rules mentioned above. Its interesting game and becomes difficult as you fill in the slots. Play it when you have free time.

My point to put this game on my post is to design this game. I will post my design and point out why i have used certain design patterns by explaining them. I would like to know how you would design such a game?

Post your comments..