ExtraLife

ExtraLife is a decentralized, no-loss prediction market protocol that lets users speculate on real-world outcomes without risking their original funds. Instead of traditional betting, all user deposits are pooled into an ERC-4626 vault and supplied to Aave V3 to generate yield. Participants vote on outcomes using only the interest earned by the pool.

When a market resolves, every participant, winners and losers alike, withdraws 100% of their principal. The generated yield is then distributed: 60% to users who predicted the correct outcome and 40% to the market creator, incentivizing high-quality, engaging prediction questions. Rewards are time-weighted, encouraging early participation and preventing last-minute whale manipulation.

ExtraLife integrates ENS for human-readable identities and profiles, and LI.FI for seamless cross-chain deposits, making participation easy from any EVM chain. The result is a fair, capital-efficient prediction market where users can engage, speculate, and earn without ever losing their money.

ExtraLife was built on top of Scaffold-ETH 2, which served as the foundation for rapid full-stack Ethereum development and clean separation between contracts and frontend. On the smart contract side, we used Solidity v0.8.20 with Foundry, implementing an ERC-4626 compliant NoLossVault that routes LINK deposits into Aave V3 on Base Sepolia to generate yield while preserving principal. Inflation-attack mitigation was handled via dead-share minting at vault initialization. A separate MarketController contract manages pool creation, voting, time-weighted stake accounting, and yield distribution.

The frontend was built with Next.js 15, TypeScript, Tailwind CSS, and DaisyUI, leveraging Scaffold-ETH’s app structure and utilities. Wallet connections and contract interactions use wagmi, viem, and RainbowKit. ENS was integrated using wagmi hooks to resolve names, avatars, and text records, improving UX by replacing raw addresses with human-readable identities. LI.FI was integrated via its widget to enable cross-chain swaps and bridges directly into the vault token, allowing users to fund positions from any EVM chain.

Notable implementation details include time-weighted yield calculations to prevent last-minute whale manipulation and real-time yield previews in the UI using live Aave APY data.