Chen — dx/dt = a·(y − x), dy/dt = (c − a)·x − x·z + c·y, dz/dt = x·y − b·z. Classic 3D ODE (a=35, b=3, c=28). RK4, not four-wing Qi lobes, not Dadras multi-scroll, not Sprott Case A, not Lorenz butterfly. Gold low-alpha trail, cap 650. RM = settled silhouette, no animate-on.