In the wasteland world after the nuclear war, humans hide in underground bunkers to survive. Every 10 days they receive a "doomsday code" that must be cracked within 24 hours, otherwise the bunker's defense system will automatically shut down, allowing mutant beasts to invade. There are various forms of passwords (such as symbol combinations, word puzzles, logical reasoning questions), and the clues to crack the passwords are scattered in various dangerous areas of the wasteland, and are full of traps (such as "radiation fog" where the clues are located, which will interfere with cognition)
