Roots and Light

Large Magellanic Cloud, planet Galle. A locust tree brought from the earth has fed three generations of people. Lin Jian was waiting for someone under the tree. His name is Liu Huaian, and he is the discoverer of the "door" thirty-one years ago. The door leads to a reduced-dimensional four-dimensional civilization - they existed and were glorious, and then were completely erased from time and space, leaving only broken ruins trapped in the gaps of the three-dimensional world. Liu Huaian once went in. After he came out, he never mentioned anything inside.