Twenty moves. One ladder.
Every sudoku solver works through a fixed set of patterns — singles to chains, easy to brutal. We walk each one in plain English, with a worked example on a small board, so you can pick the next rung on the ladder without leaving the page.
Beginner
The moves you'll lean on every solve. Learn these first.
Intermediate
Elimination patterns that get medium and hard puzzles moving again.
Pointing line
When a digit's only homes inside a box all share a row or column.
Box-line reduction
The mirror move: a digit on a line is trapped inside one box.
Naked pair
Two cells in a unit hold the same two-digit candidate set.
Hidden pair
Two digits fit in only the same two cells, even when those cells look busy.
Naked triple
Three cells share a three-digit pool between them.
Hidden triple
Three digits share a three-cell pool between them.
Naked quad
Four cells share a four-digit pool between them.
Hidden quad
Four digits share a four-cell pool between them.
Advanced
Fish and wings — the rung where the puzzle stops giving you free moves.
X-Wing
A digit's homes in two rows form a 2×2 box across the same two columns.
Swordfish
Three rows confine a digit to three shared columns.
Skyscraper
Two rows hold a digit in two cells each, sharing one column.
Two-string kite
A row and a column tie into the same box, with two ends hanging out.
Empty rectangle
A digit's candidates inside a box collapse onto one row and one column.
Y-Wing
A pivot cell and two peer wings that pinch a common digit.
XYZ-Wing
Y-Wing's three-candidate-pivot cousin.
W-Wing
Two matching bivalues, tied together by a strong link on one digit.
Expert
Chain logic and uniqueness arguments — the heavy machinery for tough grids.