Sudoku

How to play

Fill the 9×9 grid so that every row, every column and every 3×3 box contains each digit from 1 to 9 exactly once. Some cells start filled in; use logic to work out the rest. Select a cell, then pick a number. A wrong number counts as a mistake — after 3 mistakes the puzzle is over. Every puzzle is generated fresh and has exactly one solution, and the difficulty depends on the solving techniques it needs: Easy and Medium only need singles, Hard needs pairs and pointing, and Expert needs X-Wings, Swordfish or XY-Wings.

Tips

• Start with the digits that already appear most often — they leave the fewest places to go.
• Turn on notes and pencil in candidates for a box when you get stuck; pairs and triples jump out.
• Tap a number to highlight every copy of it, then scan for the rows and columns it is still missing from.
• Speed counts: every difficulty has its own leaderboard of fastest solve times.