Wang–Sun — dx/dt = a·x + c·y·z, dy/dt = b·x + d·y − x·z, dz/dt = e·z + f·x·y (b=−0.01, c=1, f=−1 fixed). Classic chaotic (a=0.2, d=−0.4, e=−1). RK4, not Lü (a(y−x), −xz+cy, xy−bz), not Chen ((c−a)·x − x·z + c·y), not Lorenz butterfly, not four-wing Qi (a·x+y·z). Gold low-alpha trail, cap 650. RM = settled silhouette, no animate-on.