Sudoku · Expert
Our hardest shelf: expert puzzles with fish and wing patterns. Take your time — logic alone still gets you there.
Expert · #1
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Sudoku FAQ
What is evil sudoku?
'Evil' is the nickname many sites give their most difficult tier. Our expert shelf is that tier: the hardest 9×9 puzzles we publish, demanding the full technique toolbox.
Can expert sudoku really be solved without guessing?
Yes — and we can prove it. Every expert puzzle is machine-checked before publication: exactly one solution, reachable through a chain of logical deductions with no bifurcation. If a puzzle needed guessing, it would not be published here.
What techniques do expert sudoku puzzles need?
Everything from the hard shelf plus fish and wing patterns — X-wing, swordfish and friends — which eliminate candidates across several rows and columns at once. Meticulous, up-to-date pencil marks are what make those patterns visible.
How long does an expert sudoku take?
Thirty minutes or more is perfectly normal, even for strong solvers. Take your time — and if you stall, the Hint button teaches the next logical step instead of just filling in a cell.