Sudoku Grandmaster

Sudoku originally called Number Place, is a logic-based, combinatorial number-placement puzzle.
The objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 sub-grids that compose the grid (also called "boxes", "blocks", "regions", or "sub-squares") contains all of the digits from 1 to 9.

Additional features:
- Auto complete and remove notes.
- Save & restore game progress for solving easily.
- Provide hints.
- Selected number highlighting.
- Alert for wrong input.
- 4 Levels: easy, medium, hard, expert.인