Puzzle #24 - An Intentional Variant (Celestial Road)

This is a Celestial Road puzzle. Celestial Road is an original mashup of Moon or Sun and Country Road. Draw a loop through cell centers that enters all regions. In each region, either visit all suns and no moons or all moons and no suns in that region. The loop must alternate passing through all moons in a region, and all suns in a region. Additionally, unused cells may not be adjacent across a region boundary.

This is the only solution to the above Celestial Road puzzle. Each of the 2 regions with only suns must be "sun" regions, as entering them requires entering a sun, and all of an entered symbol must be visited by the loop. After a "sun" region, the next region must be a "moon" region, and so the bottom left must use those cells. That renders row 2, column 2 and row 3, column 3 as unused cells. By the Country Road logic, that makes row 2, column 3 a cell that must be used by the loop, which gives the rest of the solution.

puzz.link interface   penpa interface

original, broken version