Table of Contents * 📌 Why this story matters * 🛠 The setup: what Mao built and how he priced it * 🧱 The build: three days of coding, one week to app store approval * 🚀 Growth fundamentals: distribution first, product second * 📈 Paid ads and scaling: how reaction videos paid off * 🧾 The stack and recurring costs * 🧭 A