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. Theres 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.