Concave-convex world is a 3D network animation produced by Kai Chuang Society. Concave-convex world is a 3D network animation produced by Kai Chuang Society. He created countless planets and people in the concave-convex world and ruled them at will-he made some planets rich and beautiful, others barren and desolate, some people enjoyed freedom and happiness, and some people were burdened with heavy taxes and heavy labor.