BidBeasts NFT Marketplace

Contest Details

Prize Pool

• High - 100xp

• Medium - 20xp

• Low - 2xp

• Starts: September 25, 2025 Noon UTC

• Ends: October 02, 2025 Noon UTC

Stats

• nSLOC: 170
• Complexity Score: 116

About the Project

This smart contract implements a basic auction-based NFT marketplace for the BidBeasts ERC721 token. It enables NFT owners to list their tokens for auction, accept bids from participants, and settle auctions with a platform fee mechanism.

The project was developed using Solidity, OpenZeppelin libraries, and is designed for deployment on Ethereum-compatible networks.

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The flow is simple:

1. Listing:

   • NFT owners call listNFT(tokenId, minPrice) to list their token.
   • The NFT is transferred from the seller to the marketplace contract.

2. Bidding:

   • Users call placeBid(tokenId) and send ETH to place a bid.
   • New bids must be higher than the previous bid.
   • Previous bidders are refunded automatically.

3. Auction Completion:

   • After 3 days, anyone can call endAuction(tokenId) to finalize the auction.
   • If the highest bid meets or exceeds the minimum price:
     • NFT is transferred to the winning bidder.
     • Seller receives payment minus a 5% marketplace fee.
   • If no valid bids were made:
     • NFT is returned to the original seller.

4. Fee Withdrawal:

   • Contract owner can withdraw accumulated fees using withdrawFee().

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The contract also supports:

• Minimum price enforcement for listings.
• Minimum bid enforcement for bidders.
• Auction deadline of exactly 3 days.
• Automatic refunding of previous highest bidder.
• Only owner access for withdrawing platform fees.

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Actors

• Seller (NFT Owner)

  • Owns a BidBeasts NFT and lists it for auction.
  • Receives payment if the auction is successful.

• Bidder (Buyer)

  • Places ETH bids on active auctions.
  • Receives the NFT if they win the auction.

• Contract Owner (Platform Admin)

  • Deployed the marketplace contract.
  • Can withdraw accumulated platform fees.

BidBeastsNFT Structure

├── lib/
├── src/
│   ├── BidBeasts_NFT_ERC721.sol
│   └── BidBeastsNFTMarketPlace.sol

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Compatibility

• Chain: Ethereum
• Token Standard: ERC721

Set-up

git clone <repository-url>
cd <repository-folder>

forge compile
forge test

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[//]: # (known-issues-open)

None Reported! ;)

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