1. Determine whether each cell is white or black according to the following rules.
2. No numbered cell may be black.
3. A number indicates how many grid cells, including the cell itself, lie in an uninterrupted horizontal or vertical line from that cell, up to the perimeter of the puzzle, or a black cell (whichever is closer).
4. No two black cells may share an edge. All of the white cells must be connected to each other through their edges.
