_Follow along the course with this video._ --- ### SVG NFT Ok, we've gained lots of context and understand about data storage in general and the benefits of `SVGs` specifically. Let's begin creating our very own dynamic `MoodNFT` with its `SVG` art stored on-chain. At the core of the NFT we'll build is a `flipMood` function which allows the owner to flip their NFT between happy and sad images. ::image{src='/foundry-nfts/12-svg-nft/svg-nft1.png' style='width: 100%; height: auto;'} Start with creating the file `src/MoodNft.sol` and filling out the usual boilerplate. We're definitely getting good at this by now. ```solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.18; import "@openzeppelin/contracts/token/ERC721/ERC721.sol"; contract MoodNft is ERC721 { constructor() ERC721("Mood NFT", "MN"){} } ``` Looking good! We want to store the `SVG` art on chain, we're actually going to pass these to our `constructor` on deployment. ```solidity constructor(string memory sadSvg, string memory happySvg) ERC721("Mood NFT", "MN"){} ``` We know we'll need a `tokenCounter`, along with this let's declare our `sadSvg` and `happySvg` as storage variables as well. All together, before getting into our functions, things should look like this: ```solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.18; import "@openzeppelin/contracts/token/ERC721/ERC721.sol"; contract MoodNft is ERC721 { string private s_sadSvg; string private s_happySvg; uint256 private s_tokenCounter; constructor(string memory sadSvg, string memory happySvg) ERC721("Mood NFT", "MN"){ s_tokenCounter = 0; s_sadSvg = sadSvg; s_happySvg = happySvg; } } ``` Now we need a `mint` function, anyone should be able to call it, so it should definitely be `public`. This shouldn't be anything especially new to us so far. ```solidity function mintNft() public { _safeMint(msg.sender, s_tokenCounter); s_tokenCounter++; } ``` And now the moment of truth! As we write the `tokenURI` function, we know this is what defines what our NFT looks like and the metadata associated with it. Remember that we'll need to `override` this `virtual` function of the `ERC721` standard. ```solidity function tokenURI(uint256 tokenId) public view override returns (string memory){} ``` ### Wrap Up Our on-chain, dynamic, `SVG NFT` is slowly coming to life! In the next lesson, let's walk through the contents of our `tokenURI` function and how we can encode our `SVGs` in a way such that they can be reasonably stored on the blockchain. See you there!