Nanoplastic Fragmentation Cascade 2D: Particle-Size Distribution

This is the 2D counterpart to the 3D weathering-chamber scene, computing the identical stochastic fragmentation cascade through a flat particle field instead of a rendered 3D volume: microplastic discs accumulate a UV photo-oxidation dose (rate set by the chosen polymer's susceptibility) plus an independent mechanical-abrasion term, and each particle's per-step fracture probability rises with dose and inversely with its own radius. Every fracture conserves area while splitting the parent into 2–4 daughters, so live readouts track simulated exposure time, particle count, the nanoplastic (<1 µm) fraction, mean diameter and total perimeter — alongside a log-binned size-distribution histogram and a running perimeter-growth chart that make the cascade's long tail toward nanometre sizes visible at a glance.