What it really does. Most golf video apps let you watch a swing: slow motion, draw a line, compare two clips. GSS reads it. It finds the body, measures the movement frame by frame and points at the cause: "your hips slid 6 cm towards the target", "your spine angle rose 8° before impact", "your hands peaked before your elbow". That moves the user from "I think something's off" to "there it is".