Sudoku
Sudoku is a popular logic-based placement puzzle game. Put the missing numbers from 1 to 9 into the grid.
Every number occurs once in every row and column and in every 3x3 block. You are given some of the numbers as clues.
Your aim is to place the rest of the numbers correctly.
First click on an empty cell, then click on a button with the appropriate digit.
Sudoku, sometimes spelled Su Doku, is a placement puzzle, also known as Number Place in the United
States. The aim of the puzzle is to enter a numeral from 1 through 9 in each cell of a grid, most frequently a 9x9
grid made up of 3x3 subgrids (called "regions"), starting with various numerals given in some cells (the "givens").
Each row, column and region must contain only one instance of each numeral. Completing the puzzle requires patience
and logical ability. Its grid layout is reminiscent of other newspaper puzzles like crosswords and chess problems. The
puzzle initially became popular in Japan in 1986 and attained international popularity in 2005.
The word Sudoku means "numbers singly" in Japanese. The numerals in Sudoku puzzles
are used for convenience; arithmetic relationships between numerals are absolutely irrelevant. Any set of distinct
symbols will do; letters, shapes, or colours may be used without altering the rules.
The attraction of the puzzle is that the completion rules are simple, yet the line of reasoning required to reach the
completion may be difficult. It is recommended by some teachers as an exercise in logical reasoning. The level of
difficulty of the puzzles can be selected to suit the audience. The puzzles are often available free from published
sources and also may be custom-generated using software.