Sudoku is a logic-based, fun, number-placement game that consists of a 9 x 9 grid filled with different digits. The main objective of the game is to fill each of the nine 3 × 3 subgrids with digits from 1-9 so that each column, each row contains the numbers from 1-9 but, the numbers 1-9 should appear exactly once in every row, column, and 3 x 3 grid. Sudoku puzzles come in an endless number of combinations ranging from very easy to extremely difficult.