- ➊ Blacken some cells of the diagram [paper] resp. color the gray cells of the diagram black or white [interactively].
- ➋ Areas of black cells must be square.
- ➌ Black squares must not be orthogonally adjacent (diagonally is allowed).
- ➍ Cells with numbers must not be blackened. The number indicates the total area of all orthogonally adjacent squares. A cell without a number must have at least one adjacent black cell.
- ➎ All white cells must form a single orthogonally contiguous area.