What Expert asks of you
An Expert grid plays like a Hard one until, once or twice, even pointing pairs and twins run dry. The step that breaks the deadlock links cells that don’t share a single unit, so you have to reason across the board. Because it’s so rare, the trick is knowing which pattern to try, and in which order.
Hunting an XY-Wing (nine puzzles in ten need one)
- Find the cells with exactly two notes. With Fill notes on, they stand out as cells with only two small digits.
- Pick one as the pivot, say it holds 4 and 7.
- Among the two-note cells it can see, find one holding 4 and some other digit, say 4 and 2, and another holding 7 and the same other digit: 7 and 2.
- Whatever the pivot turns out to be, one of those two ends up as 2. Any cell that can see both of them loses its 2 note.
Work through the two-note cells one by one as pivots; it takes a minute and usually finds the step.
When it isn’t an XY-Wing
Pick one digit and write down, row by row, the columns where it can still go. If two rows give the same two columns, that’s an X-Wing: those two columns get the digit from these rows, so any other note for it in those columns can go. Three rows sharing three columns between them is a Swordfish. Triples are the twins idea stretched to three cells: three cells in a unit whose notes, together, are only three digits.
Keep the notes honest
Every one of these patterns relies on complete, correct candidates. A single wrong digit placed earlier can hide the pattern or fake one. If nothing works, switch on the mistake checker for a moment, or ask for a hint: it points out a wrong digit before anything else.
Expert is the daily puzzle every Saturday. Expert grids here keep 24 to 32 givens; the level comes from the reasoning, not the count.