In the aftermath of Judgment Day, we fled to the Exclusion Zone and sought refuge underground. This is what is left of our fallen civilization.

Overwatch's Mei Is Becoming A Symbol Of The Hong Kong Resistance
https://kotaku.com/overwatchs-mei-is-becoming-a-symbol-of-the-hong-kong-re-1838899963
https://news.ycombinator.com/item?id=21203226