The Doomsday Technology Tree Lights up the Water Purification Plant at the Beginning

Thirty years since Starfall. Beside the ditch on Gray Street in Longmen City, the laundry woman used iron-containing water to wash clothes that would never be clean. It is common for children to have diarrhea for three days after drinking dirty water. An old well supports 300 households, and water sellers rely on it to collect protection fees. Lin Bei is a scavenger in Gray Street. Nineteen years old, the seventh day since my father disappeared. Carrying the copper medal left by his father, he walked into the cold storage of an abandoned supermarket and touched a glowing fragment. A tree lights up in my mind. Technology tree. The branches extend to invisible heights and are hung with hundreds of gray nodes—all the technology mastered before the destruction of human civilization. Only one node is on: basic water purification. Daily production of 500 liters of drinking water. No power grid required. No pills required. Pour in the dirty water, and after three seconds, clear water will flow out from the other end. In the apocalypse, water is the hard currency at the top of the pyramid. The device in Lin Bei's hand is not a water purifier - it is a miniature water plant. It is the life of three hundred households in Gray Street. It is a threat that makes water sellers unable to sit still. It is a bargaining chip that the five major forces cannot avoid. The day the first bucket of water went out, there was a line on Gray Street. The water seller's men blocked the door that night. But that's not what Lin Bei cares about. He stared at the second node on the technology tree that was glowing slightly - fragmented energy storage. The third and fourth are still in the dark. And the lines of words that his father had chiseled on the back of the bronze medal before he disappeared are being pieced together with scattered fragments to piece together the answer. Clean water is just the starting point. The goal of that tree is higher and deeper.