Aging & Thermoregulation 2D: Core/Shell Heat-Balance Chart

This is the 2D counterpart of the core/shell bioheat simulator: the same lumped physiology — vasomotor control of skin blood flow, eccrine sweating and shivering thermogenesis, all blunted with age — but read out as a live strip chart of core and skin temperature over time plus a phase-plane trajectory of T꜀ against Tₛ, alongside a compact core/shell diagram. Push ambient temperature, activity and clothing to stress the system, then compare a young adult against a frail elderly patient with the age slider and watch the trajectory drift further and faster toward the hypothermia or heat-stroke corner of the phase plane for the same environment.