Twenty techniques every sudoku solver should know, organized from the singles you'll find on easy puzzles up to the chain reasoning that cracks the toughest ones. Each page is plain-language with a worked example — and a daily puzzle to practice on.
Foundational placements you'll use on every puzzle.
Elimination patterns that unstick most medium and hard puzzles.
A digit confined to one row or column inside a box.
A digit in a row or column trapped inside one box.
Two cells in a unit sharing exactly the same two candidates.
Two digits that fit in only the same two cells.
Three cells sharing only three candidate digits between them.
Three digits that fit in only the same three cells.
Four cells sharing only four candidate digits between them.
Four digits that fit in only the same four cells.
Fish and wing patterns — the bridge into expert solving.
A digit locked into the same two columns across two rows.
X-Wing's bigger sibling: three rows, three columns.
Two rows where a digit has two candidates each, sharing one column.
A row and column where a digit has two cells, anchored in a shared box.
A box where a digit forms an L, paired with a strong link outside.
A bivalue pivot with two bivalue wings sharing a common digit.
A trivalue pivot pinching a digit across three cells.
Two matching bivalue cells connected by a strong link.
Chain and uniqueness reasoning — the techniques that crack the hardest puzzles.