A first-person slide down the inside of a tube that has been tied into a torus-knot. Rather than raymarch the knot, the shader rides its Frenet frame: the arc-parameter sweeps forward, banking the tunnel through every curve and rolling the whole field as the frame corkscrews, so the glowing ribs spiral past and the horizon keeps tipping like a rollercoaster. The arc surges and eases — quickening through the tight bends where the ribs flush from cyan to hot magenta — and a swell of brighter rings travels down the bore ahead of you. Hover to lean into the turns, scroll to feed the twist, and press to open the throttle.