Sudoku - Number Sort Puzzle

What is Sudoku Number Puzzle Classic Game?
Sudoku originally called Number Place is a logic-based,combinatorial number-placement puzzle.
In classic sudoku, the objective is to fill a 9×9 grid with digits so that each column, each row, and each of the nine 3×3 subgrids that compose the grid (also called \"boxes\", \"blocks\", or \"regions\") contain all of the digits from 1 to 9.

How to Play Sudoku Offline Puzzle:
Fill in the remaining boxes as long as:
* Horizontal rows:
Must have enough numbers from 1 to 9, do not have the same number and do not need the correct order.
* Vertical lines:
Make sure to have enough numbers from 1-9, do not have the same number, do not need to be in order.
* Each 3 x 3 area:
Must have numbers 1-9 and do not have the same number in the same 3 x3 area.

About our Sudoku Legend:
Our Sudoku app brings the worldwide famous Sudoku math problem to your phone. You can play it every day to improve your logical thinking ability, intellectual training.
Easy to train your brain for free & offline

* Modes:
Easy, medium, hard, expert.
* Internet Connection
No need internet connection to play our game. This is an offline game.
* Maps:
Unlimited maps to play
* Ads:
We have only one Ads banner at the bottom of screen. You also can watch a full screen ads to gain special support items.
* Support Items:
Note, Rule out, Undo, Hint, Erase
* Graphics:
Simple graphics with black and white color help you easy to see
* Sounds:
Cool Sound Effects
* Thousands of Sudoku puzzles are updated daily.

Please help us to improve this game by leaving a feedback about this sudoku Classic game.
Thanks.

Reference resources :
Sound:
https://freesound.org/people/tim.kahn/sounds/43448/
https://freesound.org/people/NenadSimic/sounds/171697/
https://freesound.org/people/Mellau/sounds/506053/
https://freesound.org/people/Autistic%20Lucario/sounds/142608/
https://freesound.org/people/grunz/sounds/109662/