Hidden Single
Exactly one candidate fits in a unit (row/column/box). Place it.
- Find units where a digit appears only once among candidates.
- Place that digit; update notes.
Learn
Sudoku Techniques
Short, practical explanations of core Sudoku strategies. Learn them here and practice in Classic Sudoku for Android.
Naked Single
A cell has only one candidate. Place it.
X‑Wing
Two rows (or columns) form a rectangle with a shared candidate. Eliminate that candidate from the columns (or rows) that see them.
XY‑Wing
A three‑cell pattern with a pivot and two pincers. Eliminates the shared candidate in their common peers.
Jellyfish
An extension of X‑Wing to four rows/columns. Great for advanced eliminations.
W‑Wing
Two bi‑value cells connected by a strong link. Removes the other candidate in common peers.
How to practice
Open the app, enable pencil notes, and try the technique on an appropriate difficulty. The Learning engine can suggest a step, and the smart hints explain why it works.