# Sudoku Puzzle Rules

Solving a sudoku puzzle can be rather tricky, but the rules of the game are quite simple.

A sudoku puzzle is a grid of nine by nine squares or cells, that has been subdivided into nine subgrids or "regions" of three by three cells. See the following diagram:

The objective of sudoku is to enter a digit from 1 through 9 in each cell, in such a way that:

- Each horizontal
row(shown in pink) contains each digit exactlyonce- Each vertical
column(shown in yellow) contains each digit exactlyonce- Each subgrid or
region(shown in green) contains each digit exactlyonce

This explains the name of the game; in Japanese, *sudoku* means something like "numbers singly".

Solving a sudoku puzzle does **not** require knowledge of mathematics; simple logic suffices. (Instead of digits, other symbols can be used, e.g. letters, as long as there are nine **different** symbols.)

In each sudoku puzzle, several digits have already been entered (the "givens"); these may **not** be changed.

The puzzler's job is to fill the remainder of the grid with digits –respecting, of course, the three constraints mentioned earlier.

A "good" sudoku puzzle has only **one** solution.

In spite of the game's apparent simplicity, sudoku can be *highly* addictive... While the first sudoku puzzle was published as early as 1979 (back then, it was called "Number Place"), the game's popularity really took off in 2005; it can now be found in many newspapers and magazines around the world.