Expert Sudoku

About Expert Sudoku

Expert is our evil tier: pairs and triples are just the opening move, and most puzzles need at least one XY-Wing or Swordfish before they fall. An XY-Wing chains three cells' candidates together to find a single elimination; a Swordfish is an X-Wing's bigger sibling, spanning three rows or columns instead of two. It's slow going, but it's still pure logic start to finish — no puzzle here has ever needed a guess.

• Write out full candidates before hunting for wings or fish — trying to hold an Expert grid in your head rarely works.
• An XY-Wing is easier to spot once you've found two cells that share exactly one candidate with a third.

Too much? Hard is a step down.