交互式3D讲解：肿瘤如何生长、侵袭与扩散

Build an interactive 3D educational simulation that explains how cancer develops and spreads, as a self-contained web app. Show a layer of soft pink cells sitting on a translucent basement membrane above a blood vessel with red blood cells. Guide the viewer through numbered steps: healthy tissue, one cell with DNA damage that escapes cell death, uncontrolled division into a tumour, a necrotic core releasing VEGF signals, new blood vessels growing toward it, invasion through the membrane, and spread to other places. Each step has a short caption at the bottom, a text panel in a corner with a plain explanation, floating labels on key structures, and a progress indicator. Add play, pause, replay and step controls, plus orbit camera control. Use a calm pastel palette with deeper reds and purples for diseased cells. Done when all steps play in order with smooth camera moves and readable text.