In 2149, the "Great Nirvana" entered its thirtieth year. A "grey dome" with a diameter of one million kilometers envelopes the earth, cutting off sunlight and the starry sky. The remaining humans huddle in the "fortress city" under the shadow of the dome, surviving on depleted fossil energy and mutated biological resources. The dome is not only a physical barrier, but also continuously releases "corrosive radiation", eroding biological genes and metal structures. The ruins of the prosperous civilization in the past have long been reduced to a "rotten wilderness" where mutated organisms are rampant.
