Tigan (T-system, Tigan & Opris 2008) — dx/dt = a·(y − x), dy/dt = (c − a)·x − a·x·z, dz/dt = x·y − b·z with b=0.6 fixed. Classic a=2.1 c=30. Dual a+c sliders. Distinct from liu-chen.html, liu.html, zhou.html, chen.html (Chen–Ueta +c·y), chen-celikovsky.html, chen-lee.html, lu.html. Bulk centroid ≈ (−0.0176, −0.0167, 12.5000). RK4 Tigan fold. Gold low-alpha trail, cap 650. RM = settled silhouette, no animate-on.