- 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 (maybe none).
- ➌ Black cells must not be
orthogonally adjacent (diagonally
- ➍ Stripes of adjacent white cells must not span across more
than two region borders horizontally or vertically.
- ➎ All white cells must form a single
orthogonally contiguous area.