The shape of a massless physics body in terms of a free form sequence of line segments. Collision occurs at its sides. When closed, the last link connects to the first. It is expected that self-intersection does not occur. It properly handles ghost collisions compared to multiple EdgeShapes: https://box2d.org/posts/2020/06/ghost-collisions/ Box2D and Aether.Physics2D call this a ChainShape, but it's not a physical chain.