React Mastery is like a personal React mentor that lives in your browser – it teaches you by letting you build, then helps you identify where you're going right or wrong, line by line. 54 challenges that build on each other, building full apps like: Component Builder Form Builder Hook Explorer Render Lab - Built-in Pedagogy System - "Mental Model" tab with: - Line-by-line explanations - "why" & How explanations - No Setup Required - Challenge completion tracking - The Mentor Engine