Light thrown off churning water onto the stone under a bridge, pushed well past realism into a riot. Three coloured lamps — cyan, magenta, amber — shine on the canal from behind you and never stop swinging; every ripple is a small curved mirror, so each lamp throws its own net of caustics across the wall and the bridge's underside, and where the nets cross they mix to white. The water's slopes are exaggerated two to three times past what real water could hold, so the nets fold and re-knot as they drift and a ripple a few millimetres high flings a line across the wall. The water is a damped wave equation on a 5 cm grid, simulated on the CPU over an analytic swell; each frame, for each lamp, every lit cell's ray is reflected off its normal and followed to the wall or soffit, and the cells form a mesh drawn where their light lands, weighted by how much its patch of water was squeezed on the way, so the folds where neighbouring rays overtake each other blaze as lines. The view is ray-traced and the water mirrors it all. Everything moves slowly and continuously: the swell runs at a fraction of real speed, the lamps drift on long sways, and the scene breathes between calmer and wilder over forty seconds, and every minute or so the swell eases away to a near-mirror calm — the nets relax into one soft glow — before it returns. Drag across the water, or across the light on the wall, to churn it; press to drop a stone.