Precious Dark is a tabletop roleplaying game set far into the future, about 120 years after the Earth's surface was deemed no longer fit for habitation. Some people still wander around up there lost, sick, barely human really anymore, but most of humanity has found a way to thrive in the Dark - a set of natural and man-made underground caverns, some of which contain entire cities full of people. These cities began as underground bomb shelters, mines, abandoned Subways, cities underneath cities - anywhere humans could think to go to get away from the dangers of the surface.
To live in the Dark, people had to find a renewable energy source that would provide them with the light and energy required to provide them stable sources of food, heating and cooling, clean air, and clean water. In that, people found The Weird. The Weird is a gas that vents through the cracks and crevices in the cave system. It is entirely odorless, and radiates a glowing spectrum of all the colors of the rainbow (and likely some that humans can’t see). When mined, The Weird is collected into cubes that can then be used as individual power sources like batteries.
Everything The Weird touches mutates in some way - the more direct the exposure, the more likely the mutations. Humanity has grown their food under Weird-powered lights, lived under Weird-powered lights, created Weird-powered transportation and technology, and as a result they've mutated. Generally speaking, the mutations are beneficial to the mutated. It's a bit like a rite of passage.
Because The Weird is so unpredictable, people in the Dark tend to do a lot of exploring. Strawberry-flavored tomatoes might grow on a vine one week, then be completely barren the next. Continuing to explore all of the cave systems in the earth's crust provides new materials for commerce, agriculture, and more. Even artists like to explore to find their favorite pigments in the bioluminescent caves, or find just the right clay, rock, stone or crystal for their next masterpiece.
Adventures occur both by exploring new places in the caves down below and by venturing into the dangerous and apocalyptic surface world that's been ravaged by everything from nuclear blasts to environmental collapse. Past games have had characters exploring prehistoric Weird-based cultures, exploring massive caverns full of Weird-infused wonders, fighting of Zombies in a Walmart, and befriending ooze-controlled dinosaur bones.
Take a look at the playtest document for more information about the world, rules, and some example characters and character sheets.
Also, check out some of the games I've already run to the left as well as some of the videos from the campaign I'm currently running.