Sudoku is a logic-based number placement puzzle. The objective is to fill a 9x9 grid
so that each column, each row, and each of the nine 3x3 boxes (also called blocks or
regions) contains the digits from 1 to 9, only one time each (that is, exclusively).
The puzzle setter provides a partially completed grid.
Completed Sudoku puzzles are a type of Latin square, with an additional constraint on
the contents of individual regions. Leonhard Euler is sometimes incorrectly cited as
the source of the puzzle, based on his work with Latin squares.
In this game, both players simultaneously try to
solve the same grid, and the one who supplies the most correct missing numbers wins.