Color each square white or black. Click to blacken a square, click again to white it, again to re-gray it. (or shift-click to white); The numbers indicate how many white squares can be 'seen' horizontally and vertically from the cell. Cells see themselves. They do not see thru black square. ALSO: All white cells must be connected as a single polyomino: a continuous path attached at edges Each black cell MUST be isolated from other black cells (not attached at edges).