Sudoku is a type of puzzle popularized by a Japanese company. It is a number-placement puzzle in which you have a grid with nine by nine squares, some of which will contain numbers. You must fill in the rest of the numbers by figuring out a way to place the number 1-9 so that the same number does not occur more than once in every horizontal line, every vertical line, and every marked box of 3x3, 9 contiguous squares. There are many different versions of sudoku, such as hypersudoku, jigsaw sudoku and greater-than sudoku. Play the classic as well as the newer versions of sudoku here!