After the Cataclysm: I Build a Super Fortress at the End of the World

[The end of the world + rebirth + King Gou + shelter + upgrade + stocking up on supplies] A sudden geomagnetic storm swept across the world, radio waves were interrupted, and the city's heating system failed. The whole world seemed to have returned to the primitive era. Food and water sources became scarce. People began to compete for limited resources in order to survive. The city has turned into a chaotic and dangerous battlefield. The law of the jungle becomes the only survival criterion. Qin Yang died in a cold room in his previous life In this life, Qin Yang accidentally obtained the shelter upgrade system [Reinforced steel door]-[Multi-locking explosion-proof door]-[Biometric security door]-[Full-function intelligent protective door] [Portable Generator] - [Multi-fuel high-efficiency generator] - [Integrated Energy Generator] - [Nuclear Power Grid System] [Hand Crossbow] - [Alloy Crossbow] - [High Performance Tactical Crossbow] - [Ultimate Customized Crossbow] While others were still worrying about food and water, Qin Yang was worrying about which upgrade route to choose. With the death of the previous life, Qin Yang vowed to survive until the end in this life It makes sense for my shelter to be able to produce infantry fighting vehicles~