Sudoku (also known as "Number Place") is a placement puzzle. The puzzle is most frequently a 9 x 9 grid made up of 3 x 3 subgrids (called "regions"). Some cells already contain numbers, known as "givens".

• The goal is to fill in the empty cells, one number in each, so that each column, row, and region contains the numbers 1 through 9 exactly once.
• Each number in the solution therefore occurs only once in each of three "directions", hence the "single numbers" implied by the puzzle's name.