Sudoku is a logic-based, combinatorial number-placement puzzle. The puzzle was popularized in 1986 by the Japanese puzzle company Nikoli. There are several types of this game: Mini Sudoku, Cross Sums Sudoku, Killer Sudoku, Alphabetical Sudoku, Hypersudoku, Duidoku, etc. You can know the rules and play this game here: http://thesudokugame.net/