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 are that you should fill a number in to every cell in the grid, using the numbers 1 to 9. The restriction is that 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!