The save of the current game will be lost.
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1sudoku.com Sudoku - Hard - n° 312391
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Hard Sudoku
You play hard level puzzles, well done, because you are part of the family of good Sudoku players. Indeed, hard sudoku calls for advanced level techniques and good deduction logic. In free online hard sudoku, you can help yourself to the candidates in each square and use logical techniques.
How do I play Sudoku?
The goal is to fill the grid, so that each row, each column and each region of 3x3 cells contain all the digits from 1 to 9.
Glossary of game options:
Clear the contents of the box
Undo the last move
Visual aid
Redo last move
Automatic selection of boxes on hover (on computer)
Show all possible candidates on the grid
Show / Hide solution
Why play hard sudoku?
Hard sudoku can be useful in a progression of learning advanced solving techniques,
but it is also played by amateurs and professionals of sudoku.
is an excellent training in techniques of detection of duplicates, triplets and other techniques.
A little more effort and you will become an expert (if you haven't already).
Play sudoku with 5 difficulty levels: easy, medium, hard, expert, evil