Sudoku

Expert puzzles bring in pointing pairs, box/line reduction, and the occasional X-Wing. These techniques all work the same way at their core: find a constraint that limits where a number can go, then use that constraint to eliminate candidates elsewhere on the grid. The tricky part isn't the technique itself — it's spotting the constraint in the first place.

Pointing pairs are the most common addition at this level. If a candidate within a 3x3 box is confined to a single row, that number can't appear anywhere else in that row outside the box. The reverse works too — if a candidate in a row only exists within one box, remove it from other cells in that box. These are small eliminations, often just one or two candidates removed, but they regularly unblock chains of deductions that were otherwise stuck.

X-Wings are rarer but more powerful. They form when a candidate appears in exactly two cells in each of two different rows, and those cells line up in the same two columns. The candidate must go in one diagonal pair or the other — either way, you can eliminate it from the rest of those columns. When an X-Wing clicks, it usually cracks the middle of the puzzle wide open.

At this level, a methodical approach matters more than speed. Check your candidate lists carefully, work through each technique in order, and trust the logic. Expert puzzles start with around 23 to 26 clues. If this difficulty starts feeling routine, our Einstein puzzles throw everything at you simultaneously.