To enter a number click on the square where you want to insert it and type in using the keyboard. If you want to add additional numbers as pencil notes then click on options and tick the pencil marking box. The options also allow you to set the timer and help options. Difficulty settings are set at the top of the page. Good luck!

These are the tips and techniques you can use to solve sudoku puzzles. Some of them are quite easy, others are tougher to get. They will, however, allow you to solve every sudoku, even the hardest ones. Read and study each tip carefully to master it and use it wisely during your play.

We will explain each technique by writing the base principle, explaining it, then giving a concrete example.

The rules of the sudoku are quite simple. A classic sudoku grid is made of nine rows and nine columns, giving 81 cells.

You must fill each cell with numbers going from 1 to 9, with the restriction that one single number can only appear once in the same row, in the same column, or in the same box of 3x3 cells.

At the game start, twenty to thirty numbers are already given and you have to find all the others. Indeed, a valid starting grid can only lead to one and only one solution. To find the missing numbers, you must use logic and observation.