Sudoku Classic is a logic-based, combinatorial number-placement puzzle game. You need to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 sub-grids that compose the grid contains all of the digits from 1 to 9 to win the game. FEATURES: Different difficulties ( Easy - Medium - Hard - Expert ). Hundreds of puzzles for each difficulty. Pencil.