Build a city, assemble a space fleet, and flee the Earth, all in 30 minutes.
https://www.youtube.com/watch?v=oBPdjvK7dyk In T-Minus 30, you explore a post-apocalyptic environment and scavenge its resources to build enough rockets to save a small pocket of humanity.
You start with a tiny settlement, where you till, irrigate, and farm the land to feed your people. As you expand, you exploit natural resources to build homes and roadways. You seek remnants of ancient civilization, mining ancient skyscrapers for their plastics and scavenging metal from the husks of automobiles you find in long-abandoned junkyards.
With those resources, you can either go high tech, building up solar farms and hydroponics labs to stock sleek generational ships that each rescue thousands of evacuees, or stay low-tech, brute-forcing your population off the Earth by building massive numbers of 1960s era rocketry.
After 30 minutes, the end comes, and you take off. You can't save everyone, but with you, there's hope for the future of humanity.
https://store.steampowered.com/app/1371750/TMinus_30/