450 classic Sudoku puzzles leveled from 1 to 9, 50 puzzles per level. Custom edit and game share also provided. Numbers can be filled with 5 different colors and combined with strike or bold font, for convenience to make mark on assumption and deduction. Smart number pad and duplicates check options for easy operation. Sudoku is a logic based puzzle. The objective is 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.