Hard sudoku
Hard puzzles cannot be finished with singles alone. At some point you need a naked pair, a hidden pair or a triple.
Hard0:00
Fill in candidates for the whole grid before you get stuck. Pairs only show up when you can see all the options at once.
When two cells in a unit share the same two candidates, those two numbers belong to them. Cross them out everywhere else in that unit.
Techniques · Printable · Daily