Cortical Granule Wave 2D: The Block to Polyspermy

A 2D cross-section of an oocyte, driven by a real reaction-diffusion PDE instead of a scripted radius. Click inside the egg to fuse the first sperm — that deposits a local calcium spike that a finite-difference solver diffuses outward frame by frame, exactly as calcium-induced calcium release does in a real cell. Cortical granules flip from unfired to fired the instant the live concentration field crosses threshold at their position, permanently hardening the zona behind the front. Click again anywhere, any time, to fire a second sperm at that exact spot: it succeeds (polyspermy) only if the simulated wavefront genuinely hasn't reached there yet, and the live "cortex covered" readout is measured directly off the grid, not assumed.