- Blacken some cells of the diagram [paper] resp. color the
gray cells of the diagram black or white [interactively].
- The black cells divide the diagram in areas of
orthogonally contiguous white cells.
- The white areas must not touch each other
- All cells with a number belong to a white area; to a white
area belongs exactly one cell with a number. The number indicates how many
cells belong to the white area.
- The black cells must not cover an area of 2x2 cells or
larger and must form an
orthogonally contiguous area.
Each region shape must be unique. This means that no two regions, including
rotation and/or reflection of the shapes, can be superimposed.