🪸 Coral Polyp Growth: Growth Speed (2D)

This 2D companion builds the same coral colony the 3D version renders, but through a canvas view designed to make the growth mechanism legible rather than decorative: new polyp buds attach by diffusion-limited aggregation, so a thin nutrient/larval "particle" random-walks down through the water column and fuses to the skeleton the instant it touches an existing tip. Because the diffusive boundary layer is always thinnest over the most exposed protrusions, flux concentrates at branch tips — the same mechanism real coral-morphology models (after Kaandorp) use to explain why staghorn coral self-organises into open, self-similar branches instead of a solid mass. A water-temperature slider drives a real bell-shaped growth curve that collapses into visible bleaching above roughly 30 °C, a depth slider attenuates light by the Beer–Lambert law and feeds a Michaelis–Menten photosynthesis curve that gates light-enhanced calcification, and a water-flow slider changes the DLA sticking probability — turbulent flow yields compact colonies, still water yields thin fractal branching, matching documented flow–morphology plasticity in real reefs.