Like a television program that creates a spin-off program highlighting a character from the original program, most successful games, especially mathematical puzzles, produce off-shoots of their own, and Sudoku is no exception.

One of the most popular variants is Hypersudoku, which is also known as NRC Sudoku, Windoku, Hyper-Sudoku, or 4-Square Sudoku. As it sounds, this game has the same layout as the normal Sudoku, but with additional interior blocks that have to contain the numbers 1 to 9. The problems to solve include the overlapping squares, which means the player has to scan and know what numbers fit into the squares and overlap squares.

Sudoku game iterations also come as overlapping and multiple grids. One that is popular is the Japanese Gattai 5 (“merged five”) Sudoku (also called Samurai SuDoku or High Five, depending on the publication in which the puzzle is found), in which five 9-by-9 grids overlap at the corner regions, forming a shape called a quincunx. Not to be left out—and as found in most Latin square puzzles (see above)—some Sudoku games come with letters rather than numbers. One of the more popular games is called Wordoku, in which the puzzle is solved using a certain amount of letters within the grid.

There are dozens of other Sudoku spin-offs. For example, there is the Sudoku version of Rubik’s Cube, called Sudoku Cube (for more about the Rubik’s Cube, see this chapter); and even a three-dimensional version of Sudoku invented by Dion Church in 2005. And, of course, there are books, magazines, and sundry websites all dedicated to not only regular Sudoku, but all the off-shoots you can imagine.