- 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.