Build an interactive coding tutor web app for absolute beginners. Core features: 1. Structured curriculum paths for HTML, JavaScript, and Python, with lessons broken into 10 to 15 minute units. 2. A browser code editor with a run button so learners see output instantly, no local setup needed. 3. An AI tutor sidebar that gives graded hints: nudge first, then a stronger hint, then a worked solution only when the learner asks. 4. Plain-language explanations of error messages, with the AI pointing to the exact line and what to change. 5. A Socratic mode where the tutor asks the learner to predict what the code will do before running it. 6. Quizzes at the end of each unit with instant feedback. 7. Progress tracking with streaks, completion badges, and a skill map showing strengths and gaps. 8. Spaced repetition review that resurfaces concepts the learner previously got wrong. 9. Mini projects at the end of each path with an AI rubric that reviews the submitted code.