Moon or Sun is a Nikoli puzzle genre.
- Draw a loop through some cells of the grid.
- The loop will pass through each region exactly once.
- In each region, the loop will either:
- Pass through all suns in the region (at least one sun), and no moons,
- or pass through all moons in the region (at least one moon), and no suns.
- In this path, the loop will alternate between passing through suns and passing through moons.