Civilized Tombstone Project

When a civilization inevitably dies, what proof should it use to prove that it ever existed? Is it the huge building that connects the planets, the thick chip filled with the history of civilization, or the melody that the last survivor sang unconsciously when he looked back at his home planet? There is a higher being who calls himself "The Observer" and reconstructs the last civilized day before the demise of these worlds. He does not interfere with life and death, but only erects monuments for civilization. Xu Yanshen was the only farewell person at these civilized funerals. He travels through one desperate apocalypse after another - either watching a lonely person spend the last day in despair before complete destruction; or wandering alone indefinitely among the silent wreckage of a giant structure. Before the world completely turns to darkness, he needs to pick out a relic that represents the dignity of his existence. Xu Yanshen is not a savior, nor can he save any civilization. He just walks among the ashes, digs out history from the dust, and leaves traces of their existence on their tombstones.