ArchiveHow to playPrintable sudokuAbout Sudoku
About expert puzzles
Expert puzzles start with 24–30 digits. Each one needs one or two advanced steps, an X-Wing or an XY-Wing, on top of everything the easier levels use. You will want full notes for this level: both patterns only show up once the options are written in.
Press New puzzle for another one at this level. Every puzzle has exactly one solution.
All five levels
| Level | Digits given | What it takes |
|---|---|---|
| Easy | 36–40 | Only naked and hidden singles |
| Medium | 28–34 | At least one pointing pair or box/line reduction; nothing harder |
| Hard | 24–32 | At least one naked or hidden pair or triple; nothing harder |
| Expert | 24–30 | One or two X-Wing or XY-Wing steps |
| Evil | 24–26 | A Swordfish, or three or more X-Wing / XY-Wing steps |
Questions
What is an X-Wing?
Two rows where a digit can only go in the same two columns. Those rows take that digit's places in both columns, so the rest of the two columns can't have it. The how-to-play page shows one from a real puzzle.
What is an XY-Wing?
Three squares with two options each, say AB, BC and AC, where the first sees the other two. Any square that sees both BC and AC can't be C, whichever way the first square goes.
How is expert different from evil?
Evil needs more of these steps (three or more), or a Swordfish, and starts with fewer digits (24–26).