Splitting expenses among friends is easy until someone disputes a transaction or quietly edits a record. Contracts addresses this trust problem by moving the entire expense-splitting workflow onto a blockchain, where the ledger's immutability means no transaction can be altered without a visible, permanent trace.

Built during Rookie Hacks II 2022, the app uses Hedera-deployed Solidity smart contracts as its backbone instead of a traditional database. Users authenticate via blockchain-based accounts and can then add, edit, settle, or delete shared expenses. Every mutation (an edit, a deletion, a settlement) is captured in an immutable audit log, so all participants always have a transparent, tamper-proof view of the transaction history. The frontend is built with Next.js and Tailwind CSS, communicating with a Node.js / TypeScript backend that interfaces with the on-chain contracts.

I built the complete frontend of the application, including the blockchain authentication flow and the transaction management UI. The most interesting challenge was working with Hedera's nascent tooling: documentation was sparse for what was then a newly-launched platform, which meant a lot of first-principles debugging to get wallet authentication and smart contract calls working together.

Contracts won Best Blockchain Project Using Hedera at the hackathon.