Enjoy and relax with this classic game that involves numbers. With our free online sudoku You can choose one of the various levels of difficulty present. In case you do not know this game yet, here are the rules:

- Each square takes a number between 1 and 9;
- In each row or column, you can not repeat numbers;
- In each of the nine 3x3 squares, you can not repeat numbers;

- very easy
- easy
- medium
- tough
- very tough
- extreme

This puzzle was designed by **Howard Garns**, a retired 74-year-old architect. Its construction was probably based on the Latin square, a mathematical construction created by the swiss mathematician **Leonhard Euler** in the eighteenth century. Garns added to the Latin square his new creation, a partially filled grid where the solver should fill empty squares. The first publications of the Sudoku occurred in the United States in the late 1970s in the American magazine Math Puzzles and Logic Problems. The numbers in the Sudoku game are used for convenience; the arithmetical relations between numbers are absolutely irrelevant (it does not require logic for mathematical calculations). Any combination of different symbols like letters, shapes, or colors could be used in the game without changing the rules. The attraction of the game is that the rules are simple, however, the line of reasoning required to reach the solution can be complex. Sudoku is recommended by some educators as an exercise for logical thinking. The level of difficulty can be selected to match the audience. There are several sources on the internet that are not linked to publishers that make the games available for free.