Ornament Pendulum Chaos on the Tree

A real double pendulum, dressed up as one bauble hanging from another on a tree branch: two rigid links, two masses, and the full nonlinear coupled equations of motion, integrated with RK4 rather than a small-angle shortcut so the genuine deterministic chaos survives. Drag either ornament to aim the starting angle, drop it, then spawn a twin that starts a fraction of a degree away and watch the two swings — identical equations, near-identical start — tear apart from each other exponentially, with a live Benettin-method estimate of the Lyapunov exponent driving that divergence.