Maybe it's a mining town that extracts some stuff that reacts really badly to sunlight, and they ran out which is why it's a ruin? (Though to be fair, drugs are a pretty good excuse.)







Though the astronomy would have to be a bit interesting. Because most planets (and their moons, if any) have orbits that look a little something like this (though their rotational axes are usually a bit more tilted--Earth's, for example, is about 22 degrees):









But when that happens, the moon and sun are usually pretty close to following the same path in the sky. There could be another option, where the orbit looks like this:











and that would put the moon in a different plane than the sun, but it would also make it so that the sun is up for like two or three months straight for a good chunk of the planet. (Which may explain why the sun is so dangerous.) (By the way, Uranus does this , but it's so far from the sun that it only changes its halves from "extremely cold" to "slightly less extremely cold".)





A third option would be to switch the sun and moon's places, so that most of the planet has a normal day-night cycle, which would get you something like this:









That would be kinda strange (how would you get a planet whose moon orbits at such a wacky angle, and do you have a big enough physics degree to work it out), but it preserves habitability for most of your planet, and also gives you the option to have interesting holidays dealing with the moon (so there could be local "First/Last Moonset/-rise" celebrations, since in a lot of places it would be up or down all the time for a few months straight).





Worldbuilding Is Fun!





Anyway, keep making interesting stuff. Pax.

