Hard Sudoku

Hard puzzles here need the techniques past singles and pairs: naked and hidden triples, X-Wings and XY-Wings. Each one is checked by a human-style solver, so it always has one answer you can reach by logic, never by trying digits until one sticks.

Fill the grid so every row, column and 3×3 box holds 1 to 9 once. Pencil marks help here: note the candidates, then look for two rows where a digit fits only the same two columns (an X-Wing) or three cells that share two candidates each (an XY-Wing). Stuck? A hint reveals a cell for two of the nine sweets.

Full rules and strategy: Sudoku · Easy Sudoku