Realm · techniques

Four patterns. Then everything.

Place one ♛ per row, column, and color region. No two queens may touch. The rest is finding the right cell.

Forced cell

One cell is the only option left in a row, column, or region.

Region 0 has only one cell left — everything else is marked impossible. So that cell must hold the queen.

A region is confined to a few rows or columns. Those rows’ (or columns’) queens must come from this region — clear the others.

Region 2 lives entirely in row 1 — so row 1's queen must come from region 2. Mark the other row-1 cells as impossible.

Two regions together span only two rows. Both rows’ queens live in those regions — and those regions can’t supply queens for any other row.

Regions 0 and 1 are confined to rows 0 and 1. So rows 0 and 1's queens both live in those regions — and those regions can't supply queens elsewhere.

A placed queen kills its 8 neighbors. If that erases all candidates from another region, the placement was wrong.

A queen blocks its 8 neighbors. If those Xs cover everything left in another region, the placement is wrong.