Sudoku-YUnderstanding the game
What makes Sudoku harder than Expert?
Hard and Expert are labels within a rating system, not universal grades. More empty cells alone do not establish a tougher logical challenge.
Consider the solving path
HoDoKu combines technique levels with accumulated step scores, using configurable thresholds. Andrew Stuart also describes puzzle generation and grading through a solving process. A clue count does not capture that process.
HoDoKu — Rating and difficulty levels · Andrew Stuart — Sudoku Creation and Grading (PDF)
How Sudoku-Y currently works
Our generator targets 43, 35, 29 and 25 clues for Easy, Medium, Hard and Expert. It keeps a clue if removing it would lose the unique solution, so the actual clue count may be higher. It does not yet certify difficulty from the techniques required by a solving path.
Expert is our highest selectable level today. It does not guarantee X-Wing or another advanced technique. Player points are also separate from puzzle difficulty ratings.
What to study next
After singles, pairs and locked candidates, try X-Wing, then explore fish such as Swordfish or chain reasoning. Aim to explain eliminations rather than collect technique names. This is Sudoku-Y’s suggested learning route, not a universal ranking.
A meaningful next difficulty level
Before adding another level, we should record solving paths, verify uniqueness and identify the techniques involved. At minimum, distinguish singles-only puzzles from puzzles requiring advanced eliminations. Removing a few more clues and changing a label would not establish that distinction.
Try before revealing
One puzzle has 25 clues and another has 29. Is the first necessarily harder?
Show explanation
No. You also need to examine clue positions, forced moves and the reasoning required to solve each puzzle.
References and further reading
Read the source explanations and compare them with our examples. Links are references, not endorsements or claims of affiliation.