Both runs use the same road array and the same speed, and the only difference
is the actuator. Passive is the dashed reference body; skyhook is the solid one.
Control law is Fₐ = −c_sky ẋ₂, force applied −Fₐ on m₁ and +Fₐ on m₂
(one internal force, both ends). Set c_sky = 0 and the two bodies must overlap
exactly. That is the passive gate, run it visually before trusting anything else.
Same equations and parameters as passive_baseline.py, re-implemented in
JavaScript and integrated with fixed-step RK4 (dt = 1 ms). Drawn roads are lightly
smoothed so pixel jaggies don’t inject fake high frequencies. “Resonance road” is a
10.7 mm sine whose wavelength lands at 1.18 Hz for the current speed, so it retunes
itself when you move the speed slider.