Global Cataclysm: My Doomsday Fortress Can Be Infinitely Upgraded

[Easy + System + Full Text No Cruelty + Versailles] Qin Jian traveled through a parallel world, but was told that the "end of the world" was coming in one week! Meteorite impact, virus spread, ice age, various experts have speculated that mankind is about to face a catastrophe. Fortunately, he is bound to the doomsday fortress system and has his own exclusive shelter. Every time he unlocks a level of the fortress, he will get various black technologies! The first floor: Light weapons production table, equipment production table, food production table. The second floor: Heavy weapons production table, tactical projectile production table, trap production table. The third floor: Chariot Technology Institute, Aviation Technology Institute. The fourth floor: Mechanical Advanced Research Institute, Gene Enhancement Library. In addition, everything in the shelter can be infinitely upgraded! When the super shelter composed of thousands of people was besieged by monsters and disappeared from sight, Qin Jian was already fully armed, stepped over the corpse of the monster, and was alone in the supermarket worrying about choosing today's ingredients. (PS: The early stages of this book are rough and the protagonist rarely stays in the shelter.)