hand-drawn 2D explainer cartoon illustration, thick clean black outlines, simplified readable forms, flat cel-style colors, soft minimal shading, expressive human characters, clean educational YouTube illustration, simple depth, clear focal hierarchy, no photorealism, no 3D rendering. Centered graphic illustration on clean white background. A 2D cartoon digital thermal gauge indicating 136°F and 100% humidity set inside a dark cavern outline with rising geothermal heat waves, occupying central 50% of frame. Large white negative margins, bright red heat indicator, flat cel colors, clean bold black outlines, no photorealism, no 3D.
