Sudoku may seem difficult at first glance, but actually it is not as hard as it looks!
The aim is to fill in the whole grid  and depending on the difficulty of the puzzle this can be quite easy (just counting and checking), or later on for more tricky puzzles require a bit more logic and reasoning.
The Rules of Sudoku
Fill a number in to every cell in the grid, using the numbers 1 to 9
You can only use each number once in each row, each column, and in each of the 3x3 boxes
Take a look at this incomplete puzzle...
The three red questionmarks are in places where there is a missing value  but it is easy to see which number to place in each.
If the rest of the line or box is complete, then by a process of elimination, you know which value must be left!

In this case, the only number missing from the horizontal row is a 3.

The number missing from the vertical column is a 9.

The value missing from the box is a 4!
Getting Started  its easy!
Until you've had lots of practise filling out puzzles, here are some questions that you can ask as you play to help you to make progress:
 Where could I place the value X in this row / this column / this box ? (Go through the numbers 1 to 9, and scan to see if the number is already in that row / column / box)
 What value could I put in this cell? (If there's just one acceptable  put it in!)
 What row / column / box is nearly full, and can I fill it?
Finally some thoughts:
 Don't Panic! The solution is in there somewhere!
 Don't Guess! For everything up to expert level, you don't need to guess!
 Don't Worry! It might look hard to begin with, but as you fill in more it gets easier and easier
For lots more help and explanations about Sudoku, visit our main website : Sudoku Of The Day