Permafrost Thaw (2D): Stefan Equation Active Layer Simulator

This 2D companion drives the same Stefan-equation permafrost physics as the 3D version through a plain canvas view built for reading the numbers rather than orbiting a shaded soil block: a side panel exposes the annual air-temperature swing, thermal conductivity, latent heat and permafrost-table depth, a soil-column cross-section shows the thawed active layer visibly growing and shrinking against the frozen ground beneath it, and a full-year graph of air temperature and thaw depth — scrubbable by dragging — lets you see exactly which day of the year the active layer reaches its maximum.