- Blacken some cells of the grid [paper] resp. color the
gray cells of the grid black or white [interactively].
- The black cells divide the grid in areas of
orthogonally contiguous white cells.
- The white areas must not touch each other
orthogonally.
- 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 may not cover an area of 2x2 cells or
larger.
- All black cells must form a single orthogonally contiguous area.
Additional Rules:
Each white region contains exactla two numbers. The size of the
region must be strictly between these two numbers.