6
Lesson 6: Naked Singles
⏱ 10 minIdentify cells where only one digit is possible after eliminating existing digits in the same row, column, and box.
Single candidateForced placementCandidate elimination
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Intermediate Level
Go beyond the basics. Learn powerful elimination techniques used by experienced solvers to crack Medium and Hard puzzles.
This is the second tier of the Sudoku Academy, picking up where the Beginner level leaves off. The techniques here are indispensable for anyone who wants to solve Medium Sudoku puzzles consistently, and they form the foundation you need before tackling our Hard Sudoku challenges.
Lessons 6–10⏱ ~75 min total🆓 Free
Lesson List
7
Lesson 7: Hidden Singles
⏱ 15 minFind digits that can only go in one specific cell within a row, column, or box — even when the cell has multiple candidates.
Digit frequencyUnit scanningConstraint propagation
8
Lesson 8: Pointing Pairs
⏱ 15 minWhen a candidate in a 3×3 box can only occupy one row or column, eliminate it from the rest of that line outside the box.
Box-line intersectionCandidate restrictionLine elimination
9
Lesson 9: Box-Line Reduction
⏱ 15 minThe complementary technique to Pointing Pairs: when a candidate in a line is confined to one box, eliminate it from the rest of the box.
ClaimingReverse intersectionBox elimination
10
Lesson 10: Naked Pairs
⏱ 20 minTwo cells in a unit sharing exactly two candidates and no others — eliminate those two digits from all other cells in the unit.
Pair detectionUnit eliminationCandidate reduction
Once you have completed all five lessons above, you will be ready to tackle our Hard Sudoku puzzles with confidence. Continue your journey in the Advanced level to unlock X-Wing, Swordfish, and chain-based strategies.