Humanoid bike

Teaching a simulated humanoid to ride a bike instead of moving a box. Whole-body balance through contact with an unstable object, which is Weng's case exactly.

• Unitree G1 (Menagerie) on a custom bike model; hands, feet and pelvis welded on; motor on the rear wheel.
• Ride to a waypoint; sideways shove mid-ride, hidden backpack mass, tire friction, with some values held out of training.
• Same controls for every arm: joint targets plus throttle at 20 Hz.
• Risk: no modern recipe for RL humanoid cycling. Week 2 go/no-go: can PPO keep it up in one overnight run? If not, fall back to the bike alone.