Craft Fair Sales Tracker App Builder

🛒 Build an offline point-of-sale + profit tracker for craft fairs, markets and pop-ups. ✅ 3-tap checkout, % or $ discounts, cash change helper 📦 Live stock: oversell blocked, void restores stock, low-stock alerts 📊 Real profit: COGS, tax, booth fees, net profit, cash in drawer 🎪 Compare events side by side ⬇️ Sales + inventory CSV, print report, JSON backup 🧪 Built-in self-test: 24 math checks must PASS 📄 One HTML file, no accounts or APIs