Soulbound QIE NFT

1// SPDX-License-Identifier: MIT
2pragma solidity ^0.8.20;
3 
4contract SoulboundNFT {
5    string public name;
6    string public symbol;
7    address public owner;
8    uint256 public nextTokenId;
9 
10    mapping(uint256 => address) public ownerOf;
11    mapping(address => uint256) public balanceOf;
12 
13    event Mint(address indexed to, uint256 indexed tokenId);
14 
15    constructor(string memory name_, string memory symbol_, address initialOwner_) {
16        require(initialOwner_ != address(0), "ZERO_OWNER");
17        name = name_;
18        symbol = symbol_;
19        owner = initialOwner_;
20    }
21 
22    function mint(address to) external returns (uint256) {
23        require(msg.sender == owner, "NOT_OWNER");
24        require(to != address(0), "ZERO_ADDR");
25        uint256 id = nextTokenId++;
26        ownerOf[id] = to;
27        balanceOf[to] += 1;
28        emit Mint(to, id);
29        return id;
30    }
31 
32    // Soulbound: tokens can never be transferred or approved once minted.
33    function transferFrom(address, address, uint256) external pure {
34        revert("SOULBOUND");
35    }
36 
37    function approve(address, uint256) external pure {
38        revert("SOULBOUND");
39    }
40}