Sudoku is a logic-based placement puzzle. The aim of the puzzle is to choose a number from the bottom line, and place it in the grid. Every row must contain one of each digit. So must every column, as must every 3x3 square. Each sudoku only has a unique solution that can be reached logically without guessing.

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 20 minutes, depending on your skill and experience.