Many people believe that the Sudoku comes from Japan. This is only partially true. 300 years ago, the Swiss mathematician Leonhard Euler invented a fascinating puzzle called the "Latin square" in the course of his investigations. Based on it, puzzle squares with numbers were invented in America in the 1970s.
From the U.S. they spread to Japan. There was born their name, which has survived to this day - Sudoku. It was also in Japan that they gained unexpected popularity in the mid-1980s.
The Sudoku game board takes up little space, unlike crosswords or other puzzles. The board consists of 81 cells, which are divided into small blocks of size 3x3.
Some cells are randomly filled with numbers. Your task is to fill the empty cells with numbers. The rules are simple enough which excludes multiple solutions.
Each column, row or block must contain numbers from 1 to 9. They should not be repeated within the same column, row or block. Sudoku is divided into several levels of difficulty - depending on the number of digits filled in. The fewer they are, the harder the game is.
In the image above, the parts of the board that are underlined in red, green and blue represent a row, column and block respectively.