GENIUS ACADEMY · 10 LEVELS

Learn Sudoku by understanding why.

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Sudoku Genius · Play nowSudoku SolverNaked SingleHidden SingleLocked CandidatesNaked PairHidden PairNaked TripleHidden TripleNaked QuadHidden QuadPointing PairBox-Line ReductionX-WingSwordfishJellyfishSkyscraperTwo-String KiteEmpty RectangleY-WingXYZ-WingW-WingFinned X-WingFinned SwordfishSimple ColoringMulti-ColoringX-ChainXY-ChainAlternating Inference Chain3D MedusaForcing ChainGenius Review

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Naked Single

This is the next unpractised lesson in your Academy path.

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Level 1: Naked Single
One empty cell has only one legal candidate.Level 2: Hidden Single
A digit has only one possible cell inside a row, column or box.Level 3: Locked Candidates
Candidates confined to one line inside a box eliminate that digit elsewhere on the line.Level 4: Naked Pair
Two cells in a house contain the same two candidates.Level 5: Hidden Pair
Two digits occur in only the same two cells of a house.Level 5: Naked Triple
Three cells in one house contain only the same three candidates between them.Level 5: Hidden Triple
Three digits are confined to the same three cells of a house.Level 5: Naked Quad
Four cells collectively contain only four candidates.Level 5: Hidden Quad
Four digits occur only in the same four cells of a house.Level 5: Pointing Pair
A candidate appears in one line inside a box and points to eliminations outside it.Level 5: Box-Line Reduction
A candidate restricted to one box along a line can be removed elsewhere in that box.Level 6: X-Wing
A digit appears in exactly two aligned cells across two rows or columns.Level 6: Swordfish
A candidate in three rows is restricted to the same three columns.Level 6: Jellyfish
Four rows and four columns form a large fish elimination.Level 6: Skyscraper
Two strong-link rows share one aligned endpoint and expose a roof elimination.Level 6: Two-String Kite
A row strong link and column strong link connect through one box.Level 6: Empty Rectangle
A box pattern and an external strong link force an elimination.Level 7: Y-Wing
Three bivalue cells form a pivot and two wings that force a shared elimination.Level 7: XYZ-Wing
A three-candidate pivot and two bivalue wings force their shared digit.Level 7: W-Wing
Two matching bivalue cells connect through a strong link.Level 7: Finned X-Wing
An almost X-Wing with one extra candidate produces local eliminations.Level 7: Finned Swordfish
A Swordfish with a confined extra candidate creates targeted eliminations.Level 8: Simple Coloring
Alternating strong links reveals contradictions or shared eliminations.Level 8: Multi-Coloring
Separate coloring chains interact to reveal eliminations.Level 8: X-Chain
Alternating strong and weak links for one candidate prove an elimination.Level 8: XY-Chain
A chain of bivalue cells links matching endpoint candidates.Level 9: Alternating Inference Chain
Strong and weak links across candidates form a logical implication chain.Level 9: 3D Medusa
Coloring a network of conjugate candidates exposes multi-digit contradictions.Level 9: Forcing Chain
Follow linked implications until every branch proves the same result.Level 10: Genius Review
Combine techniques and explain every elimination before committing it.