Starts with why keyword search fails — no math yet — then builds up through toy 2-number examples, real similarity math, a real embedding model running in your browser, and finally the production tradeoffs (chunking, ANN indexes) that RAG systems actually live or die on.
White → Brown: concept checks & hands-on, all free, all in-browser. Black & 1st Dan: AI-graded reasoning via your budget-capped Worker.