This is a rigid-link kinematic simulator with realistic joint limits — it is an engineering approximation, not an exact biological hand, and it does not claim to replicate exact human function.
Not modeled (future extensions): soft-tissue deformation, tendon and muscle dynamics, tactile sensing, collision and friction, pressure distribution, and physical grasp forces.
The simulation state is a plain per-axis angle record kept separate from rendering, so it can later be driven by a physics engine, motion-tracking system, or hardware controller. Drop a suitably rigged hand.glb into /public to replace the procedural mechanical hand.