Gas-Fused Tip Jar

A sovereign tip jar on Base that respects your gas limits. No backend. No bots. 100% on-chain.

"Simplicity is the ultimate sophistication."

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The Problem

Most "gas protection" tools rely on off-chain relayers, keepers, or Python scripts monitoring the mempool. Critique: If the server dies, the protection dies. Complexity breeds fragility.

The Solution: Dual-Layer Fuse

I built a system that enforces gas limits directly inside the EVM. It acts like an electrical fuse:

1. UI Layer (Prevention): The frontend estimates gas and warns the user before signing.
2. EVM Layer (Enforcement): If the network spikes locally or the UI is bypassed, the contract checks tx.gasprice opcode immediately.

Fail Fast: A revert still consumes a tiny amount of gas. By placing the withinGasCap modifier first, we minimize this cost to the absolute opcode minimum.

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Architecture

We reject the complexity of proxies (ERC-1167) in favor of Sovereign Contracts.

graph LR
    User((User)) -- "1. Create Jar" --> Factory[TipJarFactory]
    Factory -- "2. Deploy (new)" --> Jar[TipJar Contract]
    
    Supporter((Supporter)) -- "3. Tip ETH" --> Jar
    
    subgraph "Gas Fuse Logic"
    Jar -- "Check tx.gasprice" --> Check{Is High?}
    Check -- Yes --> Revert[Revert: Fail Fast]
    Check -- No --> Accept[Accept ETH]
    end
    
    Owner((Owner)) -- "4. Withdraw" --> Jar

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Design Philosophy (First Principles)

1. The Fuse (Opcode Level)

Instead of an Oracle, I check the raw tx.gasprice opcode. It is efficient, free to read, and impossible to spoof.

modifier withinGasCap() {
    // Fail fast to save gas.
    if (tx.gasprice > maxGasPriceWei) revert GasPriceTooHigh();
    _;
}

2. Sovereign Contracts > Proxies

You will notice TipJarFactory.sol creates jars using new TipJar(...) instead of Clones (EIP-1167).

function createJar(uint256 _maxGasPriceWei) external returns (address) {
    // Deploy a fully sovereign contract, not a proxy.
    return address(new TipJar(msg.sender, _maxGasPriceWei));
}

Why pay ~150k gas instead of 45k? Because on Base (L2), computation is cheap (~$0.01), but state bloat and complexity are expensive in the long run.

• Security: No delegatecall context confusion.
• Immutability: Each jar is an independent entity.

3. Pull over Push

We use the Withdrawal Pattern (Pull) instead of sending ETH automatically on every tip.

• Security: Prevents re-entrancy attacks.
• Reliability: Handles smart-contract wallets (e.g., Gnosis Safe) without gas griefing.

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Tech Stack

• Contracts: Solidity 0.8.20, Foundry (Forge)
• Frontend: Next.js 16 (App Router), Wagmi v2, Viem
• Chain: Base Mainnet

Deployments

Contract	Address	Verification
Factory	0x7CdA207B39F7648AABD5DF98c50f9AeA5f861e38	✅ Verified

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Run Locally

1. Contracts (Foundry)

# Install dependencies
forge install

# Run tests
forge test -vv

2. Frontend

cd app
npm install
npm run dev

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License

This project is open source and available under the MIT License.

Author

Built with 💙 on Base by Roman.

DM me for collaboration.