Basic guide to playing Sudoku

Soduku is a game where you are given a grid of 9x9 boxes. This grid is also split up into 9 smaller boxes, which each have 3x3 boxes.

The challenge is to fill the whole grid with numbers, but with the following three rules:

1) You can only use the numbers 1-9 in each row once
2) You can only use the numbers 1-9 in each column once
3) You can only use the numbers 1-9 in each 3x3 box once

Some of the boxes are filled in before you begin, so you have to work out where the numbers go around these while obeying the rules. The fewer numbers there are at the start, the harder it is considered.

There is a good site with free Sudoku puzzles here: Link