Sudoku is a logical number puzzle. The traditional Sudoku is a 9x9 puzzle grid made up with 81 cells. Complete the puzzle, so that each and every. Row, column and. 3x3 region. Contains the numbers 1 through 9 only once. In cases where the solution isn't immediately obvious, you're able to pencil possible candidates in a vacant cell. By touching a vacant cell, you activate it.