**Sudoku was invented by the American Howard Garns in 1979 and published under the name “Number Place”. The puzzle has undergone many changes. Today’s sudoku appeared for the first time in Japan in 1986, but it gained international fame only in 2005. What is sudoku? How to play sudoku? **

## Sudoku: game rules

Playing sudoku is very easy. Or rather, the rules of the game in sudoku are very simple, because the game itself may not be. Especially if you try your luck on more difficult boards.

The game consists in filling the board with numbers from 1 to 9 in such a way that in the same row, in the same column, and in each 3 × 3 sector marked with a bold line, there is only one same number. In other words, the same number may not be repeated twice in any column, row or marked sector.

## Sudoku game: How to start?

At the beginning choose the board with difficulty level 1. It will be a 9×9 board divided into 9 squares (each square divided into another 9 squares). Difficulty level 1 ensures that most of the fields will be filled immediately.

Start with a row, column or square, where most of the fields will be filled. Usually at level 1 there are several areas (rows, columns and fields) where only 3 or 4 digits are missing. Start with them.

First check what numbers are missing in the row (column or square). Now, in each free field try to check if the missing number will match. If, for example, 1 is missing in the row, then check if the number already appears in the given column and in the square. In this way you determine the potential places where this number can occur. However, you will quickly find out that most of the missing numbers can’t appear anywhere. By elimination, you will quickly fill a specific row (column or square).

Sometimes it happens that in a given column (square or row) you will not be able to fill the empty spaces by elimination. Then you can’t “shoot”. **Move to another place where many numbers are already filled.**

## Sudoku varieties

**There are several varieties of sudoku, which differ from each other in several details:**

- sudoku kinoku – the only sudoku variety in which interaction between players occurs. The game is designed for 2, 3 or 4 people. The game field is a square board consisting of nine 9 × 9 diagrams (729 fields in total);
- sudoku samurai consists of five X-shaped squares connected together;

in diagonal sudoku the numbers cannot be repeated also on the diagonals of the square;

three-dimensional sudoku, cube-shaped with dimensions of 9 × 9 × 9; - killer sudoku – the initial board has no numbers entered, but instead has areas marked with from 2 to 7 fields for which the sum of the numbers contained in them is given;

in magnetic sudoku, the same numbers are not allowed to touch each other in the corners of the squares; - sudoku on a larger board with more symbols (e.g. 12 × 12 board divided into 3 × 4 rectangles and 12 different symbols to arrange, 16 × 16 board divided into 16 squares of 16 numbers to arrange)