Editors' Note: The program stops working 28 days after you first use it. It cannot be re-installed.
Sudoku - Fill in the grid so that every row, every column, and every 3x3 box contains the digits 1 through 9. That's all there is to it. There's no math involved. The grid has numbers, but nothing has to add up to anything else. You solve the puzzle with reasoning and logic. Solving time is typically from 10 to 30 minutes, depending on your skill and experience.