A spark in the dark night

In the year 1962 a mysterious even happened, shifting reality. The sun burned out, billions died, people mutated into monsters. The earth was left in a state of frozen hell. Cities lie in frozen wastes, thick layers of snow and ice now bury the ruins. Only the star light peirces the eternal darkness. You are a mutant, of the few that kept your sanity after you transformed. Communities of mutants live in the ruins while the survivors live below ground in subterranean cities.