This low-angle shot shows old gray concrete walls covered with cracks and mottled water stains. Only a tiny round hole on the top of the wall reveals a small piece of light blue sky, echoing the core meaning of the original title no life behind gray walls. It conveys the strong oppressive feeling of enclosed space, as if the thick gray walls completely isolate the outside vitality. The dark low-saturation tone further amplifies the lonely and imprisoned emotion, full of strong narrative atmosphere.