Illustrated Explainer Spec

This is a complete spec for building a watercolor-style visual Wikipedia where every click drills deeper into whatever you point at. Type "photosynthesis," get a 16:9 painted explainer, click the chloroplast, get a new page zooming into that structure, infinitely. It's built on content-addressed caching so identical clicks never regenerate, and the architecture uses a thin client with server-side image model calls (Gemini in the reference implementation). The clever bit is compositing a red marker onto parent images before feeding them back to the model with strict style-consistency prompts. This is the kind of explorable explanation that feels obvious in retrospect but required someone to actually spec out the hashing, prompt engineering, and Sharp compositing plumbing.