ref: 0d86fe4b748e72fb8491a7e8bea7bb0a923b9f79
dir: /html/singles.html/
Singles <p> Black out some of the squares, in such a way that: <ul><li>no number appears twice in any row or column <li>no two black squares are adjacent <li>the white squares form a single connected group (connections along diagonals do not count).</ul> <p> Click in a square to black it out, and again to uncover it. Right-click in a square to mark it with a circle, indicating that you're sure it should <em>not</em> be blacked out.