🏦 On-Chain Piggy Bank - U2U Testnet dApp

A timelock savings dApp built for the U2U Hackathon, deployed on U2U EVM testnet.

✨ Features

• U2U Testnet Compatible - Built specifically for U2U EVM testnet

• Timelock Savings - Deposit U2U or ERC-20 tokens with custom lock periods

• No Early Withdrawals - Enforced time-based locking mechanism

• Batch Operations - Withdraw multiple matured deposits at once

• Responsive Design - Works on desktop and mobile devices

🔗 U2U Testnet Setup

1. Add U2U Testnet to MetaMask

Network Name: U2U Testnet
RPC URL: https://rpc-nebulas-testnet.uniultra.xyz
Chain ID: 0x9b4
Currency Symbol: U2U
Block Explorer: https://testnet.u2uscan.xyz/

2. Get Testnet U2U

💎 How to Use

1. Connect Wallet

• Click "Connect MetaMask"

• Ensure you're on U2U Testnet

• The app will automatically prompt you to switch networks if needed

2. Deposit U2U

• Enter the amount of U2U you want to deposit

• Set the lock duration in seconds (minimum 60 seconds)

• Click "Deposit U2U"

• Confirm the transaction in MetaMask

3. Deposit ERC-20 Tokens

• Enter the token contract address

• Specify the amount to deposit

• Set the lock duration

• Click "Approve & Deposit" (requires two transactions)

4. Withdraw

• Wait for your deposit to mature

• Click "Withdraw" on matured deposits

• Or use "Withdraw All Matured" for batch operations

🔧 Technical Details

• Frontend: Next.js 15 + React 19 + TypeScript

• Styling: Tailwind CSS 4 with custom animations

• Blockchain: U2U EVM testnet integration

• Wallet: MetaMask compatibility

• Smart Contract: Solidity timelock contract with reentrancy protection

📱 Smart Contract

The dApp interacts with a deployed smart contract on U2U testnet:

• Contract Address: 0xa612c68fB455e9b598fCFB1C46c120ED21ded5F6

• Features: ETH/ERC-20 deposits, timelock mechanism, batch withdrawals

• Security: Reentrancy protection, proper access controls

🐛 Troubleshooting

Common Issues

1. "Wrong Network" Error

   • Ensure MetaMask is connected to U2U Testnet (Chain ID: 420)

   • Use the "Switch to U2U Testnet" button

2. "Could not decode result data" Error

   • This usually means no deposits exist yet

   • The app handles this gracefully and shows an empty state

3. Transaction Fails

   • Check if you have sufficient U2U for gas fees

   • Ensure the contract address is correct

   • Verify you're on the correct network

Debug Mode

Open browser console to see detailed error messages and transaction logs.

🎯 U2U Hackathon Features

• U2U Testnet Native - Built specifically for U2U ecosystem

• EVM Compatibility - Uses U2U's EVM layer for Ethereum tooling

• Gas Optimization - Efficient smart contract design

• User Experience - Intuitive interface for DeFi beginners