What is goaltip?

GoalTip is a tipping app built for watching football matches with friends. The idea is that when someone jokingly says the losing team's fan owes everyone drinks, GoalTip lets that bet actually happen with real money, without needing a bank or a middleman to hold the funds. Each user's wallet keys stay inside their own browser, in a separate background process called a Web Worker, so the keys never touch the server. A host creates a room, which deploys a small on chain contract called a TipPool that acts as an escrow. Friends join the same room from their own devices and see a shared, live tip board. Anyone can tip a nation with USDt, a stablecoin, and that tip is only shown as confirmed once the blockchain itself proves the transfer happened. When the match ends, the host settles the pool on chain, the escrow pays out, and the board locks. The project stores only tip metadata, such as room codes, chosen nations, and amounts, never private keys. It also includes optional extras that only run locally rather than on the live website: a small on device AI coach that can read the current totals, and a peer to peer messaging feature for announcing tips between devices. The app runs on Next.js and TypeScript, with Redis used to sync rooms across devices on the live deployment, and the smart contract is written in Solidity and tested with Foundry. It targets the Sepolia test network, meaning it currently uses test funds rather than real money. Getting started requires Node 20 or later and the pnpm package manager. The project was built for the Tether Developers Cup hackathon.