Online Sudoku
How to play Sudoku?
Players need to infer all the numbers in the remaining spaces based on the known numbers on the 9×9 board, and satisfy that the numbers in each row, column, and each square (9 spaces each) contain 1 to 9, without repeating.
What is the hardest Sudoku?
According to Finnish mathematician Arto Inkala, the following puzzle of his own invention is the hardest Sudoku puzzle created so far.
