Sudoku Puzzle description

Sudoku puzzle is a logic-based, combinatorial number-placement game. In this game there is a collection of free sudoku puzzle games.
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. The puzzle setter provides a partially completed grid, which for a well-posed puzzle has a unique solution.

Features:
- A lot of different sudoku puzzles;
- Four levels of difficulty: very easy, easy, normal, hard;
- Hints;
- Save the progress in every launched game.