Rules - Straight and Arrow

Straight and Arrow was invented by the Japanese puzzle company Nikoli.  The name comes from mathgrant.

1. Draw a single loop that connects the centers of the grid cells.

2. The loop may only travel horizontally or vertically, not diagonally (so all turns are right angles).

3. The loop may only turn at the centers of the grid cells.

4. The loop may not cross itself or branch off.

5. The loop may not go through any cells with a number in it.

6. Any cell that does not have an arrow or is part of the loop must be shaded black.

7. No other cells may be black.

8. No two black cells may share an edge.

9. A cell with a number and an arrow show how many black cells are in the row or column pointed at by the arrow.