Tumor Drug-Diffusion Map: 2D Reaction-Diffusion Simulator

This simulator solves the spatial problem that a single well-mixed plasma-concentration curve can't show: chemotherapy doesn't reach every tumor cell at once, it has to diffuse there from the surrounding vasculature. A real 2D Fickian diffusion equation carries drug concentration inward from four capillary points at the edge of a tumor cross-section, competing against first-order clearance that can remove it before it ever arrives at the core. Wherever the drug does arrive, it drives a local log-kill (Norton–Simon) term against Gompertzian regrowth, cell by cell across the grid — so the simulation naturally reproduces the diffusion-limited, drug-resistant tumor core seen in real solid tumors, as a direct numerical consequence of the physics rather than a hand-drawn color gradient. Adjust the dosing schedule and the tissue's vascular diffusivity to see how a poorly perfused tumor can survive a regimen that would clear a well-perfused one.