Sudoku World - Brainstorming!!

This is an awesome Sudoku app game that allows you to play an unlimited amount of sudoku puzzles on your iOS devices.
【 Features 】
⊲ There is no possibility to get twice the same puzzle since they are randomly generated.
⊲ Added new kinds of sudoku puzzles:
X Sudoku, Super Sudoku, Jigsaw Sudoku, 16x16 Sudoku and Samurai Sudoku.
⊲ Added multiplayer mode of sudoku game:
You can play/challenge sudoku game with your friends and other sudoku player on line.
⊲ Support !!!!!! GAME CENTER !!!!!!!, 25 Leaderboards and 20 achievements.
⊲ Five levels of difficulty.
⊲ Load/Save puzzle from/to the application database.
⊲ Statistic, it saves every finished puzzles automatically, that allows you to keep tracking your best played records for each level, you can restart it whenever you want to re-challenge it.
⊲ Pause/Resume which allows you are able to take a short break from the puzzle.
⊲ Undo/Redo the selected number.
⊲ Smart note, automatically put the related note on the field, or put all notes for all fields or clear them all with only one tap.
⊲ Auto/manual check for incorrect numbers.
⊲ Smart eraser to let you remove number on the field clearly and easily.
⊲ Hint, to provide you a easy way to find out current single note field, certainly a little penalty is required :-).
⊲ Keep device from sleeping, your iPhone/iPod no longer sleep while you are thinking in a puzzle.
⊲ Smart coloring fields, allows you to see the relation of each fields while tapping on it.
⊲ In game progress indicator, to show you current progress with a bar interface.
⊲ Compatible with iOS12.0 iPod, iPhone device, Retina Display for iPhone 6/7/8/X/XS (Max) support.
⊲ Customize your own background by picking up an photo from your own album.
Any reviews and ratings are all appreciated, your comments are making this sudoku app become better!!