Wicked Strategery

"Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9."

Sudoku, Japanese for "numbers singly", is a logic puzzle where you fill in a 9x9 grid with numbers so that each digit (1-9) appears once in each row, column, and 3x3 square. Some of the numbers are already filled in, to get you started.

The puzzle appears to be easy, just filling in numbers. But the beauty lies in its simplicity - no guessing required, every number can be filled in using just logic.

Try it yourself at www.websudoku.com.

Update: I found a really good resource, Sudoku of the Day, that offers puzzles of varying degrees of difficulty as well as tactics solve the puzzles.