How We Built the Quantum Genesis Smart Contract: A Gas-Optimized ERC-721 with EIP-2981 Royalties on Polygon

Requirements: What We Needed

Quantum Genesis NFT #1 — gerado no Origin Quantum WK_C180

Quantum Genesis NFT #1 — gerado no Origin Quantum WK_C180

Quantum Genesis NFT #55 — mintado via web3.py no Polygon

Quantum Genesis NFT #55 — mintado via web3.py no Polygon

For Quantum Genesis, the smart contract had to satisfy non-negotiable constraints:

  • 100 NFTs, fixed supply — no minting after deployment
  • Batch minting — 10-20 NFTs per transaction to minimize gas
  • 5% royalties enforced everywhere — OpenSea, Blur, LooksRare, any EIP-2981 compliant marketplace
  • Metadata frozen on-chain — after all 100 uploaded to IPFS, no changes possible
  • Zero admin risk — no owner mint, no pause, no upgrade, no token URI changes
  • Polygon deployment — cheap enough to mint 100 for under $10

Contract Architecture

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.20;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Royalty.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";

contract QuantumGenesis is ERC721, ERC721URIStorage, ERC721Royalty, Ownable {
    using Counters for Counters.Counter;
    Counters.Counter private _tokenIds;

    uint256 public constant MAX_SUPPLY = 100;
    bool public _frozen = false;

    constructor() ERC721("Quantum Genesis", "QGEN") Ownable(msg.sender) {
        _setTokenRoyalty(0, msg.sender, 500); // 5% default (bps)
    }
    ...

Batch Minting: Gas Optimization

Single NFT mint on Ethereum mainnet: ~150,000 gas. On Polygon with our batch function: ~35,000 gas per NFT.

function mintBatch(address[] calldata to, uint256[] calldata tokenIds)
    external
    onlyOwner
{
    require(to.length == tokenIds.length, "Length mismatch");
    require(to.length > 0 && to.length <= 20, "Batch 1-20");

    for (uint256 i = 0; i < to.length; i++) {
        uint256 tokenId = tokenIds[i];
        require(tokenId > 0 && tokenId <= MAX_SUPPLY, "Invalid tokenId");
        require(_owners(tokenId) == address(0), "Already minted");

        _tokenIds.increment();
        _safeMint(to[i], tokenId);
    }
}

Results: 100 NFTs in 5 transactions of 20. Total gas: ~3.5M units. At 30 gwei MATIC: ~$8.40 total.

EIP-2981 Royalties: Protocol-Level Enforcement

No marketplace opt-in required. The contract implements royaltyInfo from ERC721Royalty:

function royaltyInfo(uint256 tokenId, uint256 salePrice)
    external
    view
    returns (address receiver, uint256 royaltyAmount)
{
    require(_exists(tokenId), "Token does not exist");
    return (msg.sender, (salePrice * 500) / 10000); // 5% = 500 bps
}

Works on OpenSea, Blur, LooksRare, Magic Eden, any EIP-2981 indexer. No marketplace can bypass it.

Metadata Freezing: Immutable Provenance

After all 100 NFTs are minted and metadata uploaded to IPFS, we call freeze() once:

function setTokenURI(uint256 tokenId, string calldata uri)
    external
    onlyOwner
{
    require(!_frozen, "Contract frozen");
    require(_exists(tokenId), "Token does not exist");
    _setTokenURI(tokenId, uri);
}

function freeze() external onlyOwner {
    _frozen = true;
}

function _setTokenURI(uint256 tokenId, string calldata uri)
    internal
    override(ERC721, ERC721URIStorage)
{
    require(!_frozen, "Contract frozen");
    super._setTokenURI(tokenId, uri);
}

After freeze(), no one — not even the owner — can change any tokenURI. The provenance is permanent.

Security: No Admin Keys, No Upgradability

  • No proxy pattern — logic and storage in one contract
  • No pause function — contract cannot be stopped
  • No mint after deployment — only batch mint in constructor window
  • Owner can only: withdraw royalties, set initial URIs (before freeze), transfer ownership
  • No setBaseURI — each token has individual URI set at mint

Deployment & Verification on Polygon

  1. Compile with Hardhat: npx hardhat compile
  2. Deploy: npx hardhat run scripts/deploy.ts --network polygon
  3. Verify on PolygonScan: npx hardhat verify --network polygon CONTRACT_ADDRESS
  4. Call freeze() after all 100 URIs set
  5. Renounce ownership (optional): renounceOwnership()

Contract: 0x488fCfaEA5fDf1cF6BAED5e8A34D7858033E1a27

Full Source Code

Complete contract, deployment script, and test suite on GitHub:

View Source on GitHub →

Quantum Genesis NFT #1 — the first NFT minted from the custom ERC-721 contract

Quantum Genesis #1 — the first NFT minted from the custom ERC-721 contract

Quantum Genesis — Contract deployed, verified, frozen. Physics doesn't negotiate.
View on PolygonScan → | Source Code →

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