How Do You Solve A Su Doku Puzzle?

A Su Doku puzzle is a Japanese number puzzle.  Doku means "number in Japanese.

This kind of puzzle is used because the Japanese language does not work well in English - style crossword puzzles.  It is like a crossword puzzle, only using numbers.  (You can use pictures or colors as well.)

The Su Doku board usually consists of a grid of 9 rows by 9 columns.  Each row and column is nine units long.  As they overlap, nine 3 by 3 squares are formed on the grid.

The objective is to write all the numbers 1 through 9 once each in each row and column, as well as in each 3 x 3 square.

There is only one solution.  You can find it by looking across the rows and up and down the columns.  If a row needs a 2, then you look for a place where the 2 might fit.  It does not fit in a space that has a 2 already in the column above or below it, or in the 3 X 3 square it is in.  

Su Doku puzzles range from very easy to very hard, depending on how many numbers are given to you at the start.