- ➊ Blacken some cells of the diagram [paper] resp. color the
gray cells of the diagram black or white [interactively].
- ➋ The black cells must not cover an area of 2x2 cells or
larger and divide the diagram in rectangular areas of
orthogonally contiguous white cells.
- ➌ All cells with a number belong to a white area; to a white
area belongs at most one cell with a number. The number indicates how many
cells belong to the white area. White areas not including a cell with a
number may be of any size.
- ➍ White areas may not touch each other
orthogonally; but all white areas must be diagonally connected.