Seelig — dx/dt=a−xy−εx, dy/dt=xy−y/(b+y), dz/dt=c(y−z). Classic a=0.8 b=0.15 ε=0.05 c=0.15. Dual a+b sliders. Display embed (x,y,z). Distinct from brusselator.html, selkov.html, lengyel-epstein.html, schnakenberg.html, operon.html. Bulk centroid ≈ (1.9511, 3.6753, 3.7069). RK4 enzyme fold. Gold low-alpha trail, cap 650. RM = settled silhouette, no animate-on.