Master Sudoku

One advanced pattern per puzzle

Master — listed as Evil on many Sudoku sites, and reachable here at both spellings — is defined by a single hard requirement: the solver must use exactly one advanced technique to finish. Givens range from 23 to 31.

Everything else in the puzzle is ordinary. You will place singles, spot a pair, run a pointing elimination, and then hit one position where none of that is enough. That single position is the puzzle.

What counts as advanced here

• X-Wing: one digit confined to the same two columns in two different rows, which eliminates it elsewhere in those columns.
• Swordfish: the same idea stretched across three rows and three columns.
• XY-Wing: a two-candidate pivot cell connected to two wings, forcing one digit out of the cells both wings see.
• AIC: a chain of alternating strong and weak links that rules out a candidate at the far end.

Finding the pattern instead of waiting for it

Advanced patterns do not announce themselves while you scan cells. They appear when you scan a digit: pick one digit, look at every unit where it still has exactly two possible cells, and check whether those pairs line up into a rectangle.

If you cannot find it, the hint system on this level is genuinely useful — it will name the pattern and highlight the cells that form it, which teaches the shape far faster than rereading a definition.

Expect a long sitting

A Master grid is not a five-minute puzzle, and the mistake limit makes a careless placement expensive. Take notes seriously, and treat the moment the grid stops moving as the interesting part rather than the frustrating one.