I added a few things on top of Nader’s tutorial:
You can play with the demo at https://closesea-one.vercel.app/, which uses the contract deployed on Rinkeby - you need to connect your wallet, switch to Rinkeby network, and use test Rinkeby eth to list and trade.
The listed/minted NFTs can be seen at https://testnets.opensea.io/collection/closesea-collection.
The code and docs can be accessed at Repo.
The followings are used in this project:
Manage Contract Page:
Collection on OpenSea:
Traits on OpenSea: