- ➊ Blacken some cells of the diagram [paper] resp. color the
gray cells of the diagram black or white [interactively].
- ➋ A number in a
region indicates how many cells in this region must be blackened. In
regions without a number an arbitrary number of cells may be blackened.
- ➌ Within a region the black cells must form a stone, an
orthogonally contiguous area.
- ➍ Black cells must not be
orthogonally adjacent across borders .
- ➎ If all stones »fall down«, they must cover the lower half of the
diagram completely without gaps.