Expert printable sudoku
Twenty-six clues, and every board needs a chain: a W-Wing, an XY-Chain, or — occasionally — a swordfish. Expect twelve moves, not five.
What expert actually costs
Twenty-six clues, and the solve is long. On the 600 boards this setting produced, the average solve used 12.8 technique steps — against 8.1 at hard and 1.0 at easy. That number is the real difference between the settings. It is not that the techniques are more exotic; it is that you have to keep applying them for twice as long without losing track of the board.
The techniques that finished these boards:
| Technique that topped out the solve | Boards out of 600 |
|---|---|
| W-Wing | 297 |
| XY-Chain | 279 |
| Swordfish | 23 |
| Jellyfish | 1 |
W-Wing and XY-Chain are basically tied, and together they account for 96% of the sheet. Both are chain techniques: you follow a sequence of forced moves to prove that one candidate cannot be there. Both reward the same habit — writing down what is forced before you start, rather than trying to hold the chain in your head.
One jellyfish in six hundred
Jellyfish appeared exactly once. This is worth saying out loud because most guides introduce it as the next fish after the swordfish, which implies it is the next thing you will meet. It is not. In a 5,000-puzzle sample with no difficulty filter at all, the jellyfish appeared zero times. It is a real technique, it is teachable, and it is not something you will run into by playing.
If you are hunting for one on this sheet, stop. The jellyfish article explains why the hunt is usually a waste of time and when it is not.
Printing notes
Candidate marks on, always. A chain is a sequence of candidate eliminations; without the grid printed you are reconstructing thirteen steps of reasoning from memory. Even with marks, use the margin: write the chain's endpoints next to the board before you start eliminating.
One puzzle per page. This is the one setting where the four-per-page layout actively hurts. You will write on the grid, circle cells, and draw arrows between them; there is no room for that on a quarter page.
Expect to spend 25–40 minutes per board. If you finish one in ten, you are either very good or you guessed somewhere and got away with it.
What is above this
The evil sheet is not "expert but harder". Every board at that setting defeated all sixteen techniques this engine implements — they need a guess, a chain you build by hand, or a technique that is not in the ladder. It is a different kind of wall, and it is worth knowing that before you print it.