Sudoku game - belpyro/GamePortal GitHub Wiki
Game rules
Fill in the numbers 1-9 exactly once in every:
— row;
— column;
— and 3x3 region.
https://www.kristanix.com/sudokuepic/sudoku-rules.php
https://sudoku.com/how-to-play/sudoku-rules-for-complete-beginners/
https://www.bigfishgames.com/blog/how-to-solve-sudoku-puzzles-quickly-and-reliably/