Moon-or-Sun (adapted from Nikoli)
- Draw a line to make a single loop.
- Lines pass through the centers of cells, horizontally, vertically, or turning. The loop never crosses itself, branches off, or goes through the same cell twice.
- A rectangle, bordered by bold lines, is called a "room".
- Color each room blue or yellow.
- The loop must visit each room once, alternating between blue and yellow rooms.
- In a blue room, you must visit all of the moons and none of the suns; in a yellow room, you must visit all of the suns and none of the moons.