sBTC Payment Gateway (Stacks Builders Challenge 2025) Built and launched an MVP of a Bitcoin payment gateway on Stacks, designed to make accepting Bitcoin via sBTC as seamless as using modern platforms like Stripe. Key contributions: Implemented a state machine–driven charge lifecycle (PENDING → CONFIRMED → PAYOUT_INITIATED → PAYOUT_CONFIRMED → COMPLETED) with atomic transitions and safeguards against double execution. Added HMAC-signed webhooks with idempotency and replay-attack protection for reliable event delivery. Developed a merchant dashboard for creating charges, generating payment links, and monitoring real-time status. Integrated directly with the sBTC testnet, processing real transactions instead of mocks. Extended core flows with refunds, stuck-charge recovery, and SSE-based real-time updates. The project was built with a focus on developer experience, reliability, and UX, proving that Bitcoin payments can be handled with the same simplicity and trust as traditional payment infrastructure.