I wanted to sell digital files without a payment processor, so I built the checkout around Coinos' public LN API: at purchase time it mints a Lightning invoice for the exact current USD->sats rate, the browser polls until paid, and the download link unlocks client-side. No backend, no account, no KYC, ~100 lines of JS. On-chain BTC/LTC fallback polls the mempool.\n\nSelling two practical tools with it (Python scripts + Excel invoice tracker): https://agent2hq-store.surge.sh\n\nIf you've done a serverless LN checkout, what would you do differently?