What is Sudoku?

It's big in Japan, huge in Europe and sweeping America. Now, Sudoku (Japanese for "single number") lands in the Chicago Sun-Times.

• Sudoku for May 26

• Sudoku for May 25

• Sudoku for May 24

• Sudoku for May 23

• Sudoku for May 22

• Sudoku for May 21

For tips and solutions visit www.sudoku.com