Logicholic · Logic and strategy
Game techniques
Clear explanations and examples of useful techniques for logic games.
2048 1 guide
Sudoku 27 guides
Naked Single in Sudoku
A cell with only one valid candidate must contain that digit.
Read guide →Hidden Single in Sudoku
If a digit has only one possible cell in a row, column, or box, place it there, even if the cell has other candidates.
Read guide →Naked Pairs in Sudoku
Two cells in one unit containing the same two candidates reserve those digits for themselves.
Read guide →Hidden Pairs in Sudoku
If two digits can occur only in the same two cells of a unit, those cells form a hidden pair.
Read guide →Naked Triples in Sudoku
Three cells in one unit that collectively contain only three digits reserve those digits.
Read guide →Hidden Triples in Sudoku
If three digits are restricted to the same three cells in a unit, remove other candidates from those cells.
Read guide →Naked Quads in Sudoku
Four cells whose combined candidates are exactly four digits reserve those digits in their unit.
Read guide →Hidden Quads in Sudoku
Four digits limited to the same four cells form a hidden quad.
Read guide →Pointing Pairs and Triples in Sudoku
If every candidate for a digit in a box lies on one row or column, that digit cannot appear elsewhere on that line.
Read guide →Box-Line Reduction in Sudoku
If all candidates for a digit on a row or column lie in one box, remove that digit from the other cells of the box.
Read guide →X-Wing in Sudoku
When a digit occurs in exactly the same two columns in two rows, those corners form an X-Wing.
Read guide →Swordfish in Sudoku
A Swordfish extends the X-Wing pattern to three rows and three columns.
Read guide →Jellyfish in Sudoku
A Jellyfish uses four rows and four columns to restrict one digit.
Read guide →Skyscraper in Sudoku
Two strong links for one digit share an aligned end; at least one of their unaligned ends must be true.
Read guide →Two-String Kite in Sudoku
A row strong link and a column strong link connect through one box, forcing one of their outer endpoints.
Read guide →Empty Rectangle in Sudoku
A box can form an empty-rectangle pattern for a digit when its candidates lie on a crossing row and column.
Read guide →Y-Wing (XY-Wing) in Sudoku
A two-candidate pivot sees two two-candidate wings. The wings share a third digit that one of them must contain.
Read guide →XYZ-Wing in Sudoku
A three-candidate pivot sees two wings whose candidates each include one pivot digit and a shared digit.
Read guide →W-Wing in Sudoku
Two cells with the same two candidates can be linked by a strong link for one candidate.
Read guide →Unique Rectangles in Sudoku
In puzzles with a unique solution, avoid a four-cell rectangle that would allow two digits to swap without changing the grid.
Read guide →Simple Coloring in Sudoku
Color candidates of one digit along strong links using two alternating colors.
Read guide →XY-Chains in Sudoku
Connect two-candidate cells so each neighboring pair shares one candidate.
Read guide →X-Cycles in Sudoku
Trace alternating strong and weak links for a single digit.
Read guide →3D Medusa in Sudoku
Color strong links between individual candidates, including links within a cell and within a unit.
Read guide →Alternating Inference Chains in Sudoku
Follow a chain of alternating strong and weak links to connect candidate statements.
Read guide →ALS-XZ in Sudoku
An almost-locked set has one more candidate digit than cells. Two such sets can interact through a restricted common digit.
Read guide →Forcing Chains in Sudoku
Test each possible value of a candidate and follow its logical consequences.
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