Campus Split

"Campus Split: The instant, frictionless way for students to split bills using USDC on Base."

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Inspiration

What it does

Campus Split 🎓 (USDC on Base)

Live Contract: 0xBC9B9b9c0BdBdE267352fFF668a69c25b738c163

💡 Inspiration

As university students, splitting bills is a daily struggle. "Who paid for the pizza?" "What about the electric bill?" Traditional apps like Venmo or Splitwise have friction: settlement delays, bank withdrawal limits, and they are often inaccessible to international students who don't have local bank accounts.

We wanted to build something instant, borderless, and trustless. By using USDC on Base, we realized we could make splitting a $5 lunch just as cheap and fast as sending a text message, without any bank acting as a middleman.

🚀 What it does

Campus Split is a decentralized expense settlement tool.

  1. Create a Bill: A user initiates a shared expense (e.g., "Friday Pizza Night") on-chain.
  2. Approve: Participants approve the smart contract to spend their USDC.
  3. Settle: With a single command, the contract pulls USDC from the payer and instantly pushes it to the creator's wallet.

There is no "balance to withdraw." The money moves wallet-to-wallet in one atomic transaction.

⚙️ How we built it

We utilized a robust EVM stack optimized for the Base L2 ecosystem:

  • Smart Contract: Written in Solidity ($v0.8.24$). We implemented the IERC20 interface to interact directly with Circle's official USDC contract on Base Sepolia.
  • Network: Deployed on Base Sepolia Testnet. We chose Base for its EVM equivalence and negligible gas fees, which are critical for micro-transactions ($< \$0.01$ fee).
  • Dev Environment: Hardhat for compilation, testing, and deployment scripts.
  • Interaction: We built a custom Node.js CLI (Command Line Interface) using Ethers.js to demonstrate the flow live without needing a heavy frontend.

🚧 Challenges we ran into

The biggest challenge was Dependency Hell. We initially faced severe conflicts between Node.js v22, Hardhat v2, and the newer Hardhat v3 Toolbox. The environment kept crashing with ERR_MODULE_NOT_FOUND and TypeScript mismatches.

  • Solution: We stripped the project down to a pure JavaScript + CommonJS architecture, manually managing the hardhat-ethers plugins to ensure stability. It was a lesson in "keeping it simple" to ship on a deadline.

🏅 Accomplishments that we're proud of

  • Live Deployment: We successfully deployed to the Base Sepolia testnet despite environment crashes.
  • Circle Integration: Successfully interacting with the USDC contract (approvals and transfers) rather than just sending native ETH.
  • Atomic Settlement: Writing logic that ensures the bill is marked "Settled" exactly when the funds move, preventing double-payments.

🧠 What we learned

  • EVM Tooling: We gained a deep understanding of Hardhat configuration and debugging provider errors.
  • Base Architecture: We learned how to bridge assets from Sepolia L1 to Base L2 to fund our deployment.
  • Async/Await patterns: Managing blockchain state changes and waiting for block confirmations in our scripts.

🔮 What's next for Campus Split

  • Frontend: Building a React/Next.js mobile-first UI for easy use in dining halls.
  • Group Splits: Upgrading the contract to handle $N$-way splits (e.g., 4 roommates splitting rent).
  • Base Identity: Integrating "Basenames" so users can pay @alice instead of 0x123.... ## How we built it

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