click or drag on the canvas to drop B.
the model
dA1/dt = D1∇²A1 − 2·c1·A1·B² + f1(1 − A1) dA2/dt = D2∇²A2 − 2·c2·A2·B² + f2(1 − A2) dB/dt = DB∇²B + c1·A1·B² + c2·A2·B² − (k + (f1+f2)/2)·B
Two substrates, each fed in from a reservoir, each able to react with two B to make a third. Set D1 = D2, f1 = f2 and c1 + c2 = 1 and it collapses to ordinary Gray-Scott. Pull the diffusion rates apart and B has two different kinds of food to chase: one that spreads quickly and one that stays put.
c1/c2 set how much of the B production runs through each substrate. Explicit Euler, dt = 1, periodic edges, so diffusion rates top out at 0.25.