Living Coral

Diffusion-limited aggregation in the Witten-Sander form. Brownian walkers are released one at a time from a ring outside the cluster and freeze permanently on contact, so growth follows the harmonic measure of the surface. Long jumps are taken only where a dilated occupancy pyramid proves the disc is empty, and far strays re-enter through the exact two-dimensional exterior Poisson kernel. Colour is the arrival index alone, oxblood at the seed and white-hot at the last arrivals.