Learn the techniques

The last empty cell in a row, column or box.

A cell with only one candidate left.

A digit that fits only one cell in a house.

A digit locked to one line within a box.

A digit locked to one box within a line.

Two cells sharing the same two candidates.

Two digits confined to the same two cells.

Three cells sharing three candidates.

Three digits confined to the same three cells.

Four cells sharing four candidates.

Four digits confined to the same four cells.

A digit boxed into a 2×2 rectangle.

The three-line version of an X-Wing.

The four-line fish.

A pivot and two pincers sharing a digit.

An XY-Wing whose pivot also holds Z.

Two matching pairs joined by a strong link.

Two conjugate lines sharing a base.

A row pair and a column pair joined by a box.

An L-shaped lock in a box plus a conjugate pair.

Avoiding a two-solution deadly pattern.

The digit that prevents a non-unique grid.

Two-colouring a digit's conjugate network.

A chain of identical bivalue cells.

A single-digit alternating chain.

A chain through bivalue cells.

Two almost-locked sets sharing X and Z.