Hard sudoku

What to expect at this level

Hard sudoku puzzles ask for patterns that are harder to see, because the clue is in what a cell can no longer be. Keep your pencil marks up to date. Each one is still logic all the way through, and none requires a guess.

Techniques you'll use

• Hidden pair
• Box-line reduction

Use New puzzle for another at this level. Want the toughest we have? Try expert sudoku. Go there.