Some changes to help stonercats out - NEEDS testing

stonerCats.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.7.0;

// @title: Stoner Cats
// @author: bighead.club

////////////////////////////////////////////////////////////////////////
//                                                                    //
//    __     =^..^=                                                   //
//  =^._.^=   (u u).                    =^..^=                        //
//  (_)--\_)  (   \     =^..^=___. ,--. //--//(,------.,------,       //
//  /    _ / |'--b..b__)( u u).-.\|   \ |  |) |  .---'|   ---`'       //
//  \_..`--. `--.  .--'( _) | |  ||  . '|  |d |  '--. |  |_.' |       //
//  .-._)   \   |  |    \|  | |  ||  |\    |  |  .--' |  .   .'       //
//  \       /   |  |     '  '-'  '|  | \   |  |  `---.|  |\  \        //
//   `-----'    `--'      `-----' `--'  `--'  `------'`--' '--'       //
//                                                                    //
//                                                    ((((            //
//   ,-----.  ,----.   _=^..^= __∫ _____        .,,  ((((((  .//.     //
//  /  .--./ |  /`. \ |   uu...u_)  ___/       /(((( `(((/. (((((     //
//  | =^..^= '-'|_.' |`--.  .--'\_..`--.       (((((. ..,.  /(((/     //
//  |  |u u )(|  .-. |   |  |   .-._)   \     ,,```. ((((((./(' /(\   //
//  '  '--'\ |  | |  |   |  |   \       /    ((((,, .((/((((. '((((   //
//   `-----' `--' `--'   `--'    `-----'     .((/,..(((((((((( *((,   //
//                                                 (////((((((        //
//                                                  ((//((/)          //
//                                                                    //
////////////////////////////////////////////////////////////////////////

// OpenZeppelin
import "./token/ERC721/ERC721.sol";
import "./access/Ownable.sol";
import "./security/ReentrancyGuard.sol";
import "./introspection/ERC165.sol";
import "./utils/Strings.sol";
import "./access/Ownable.sol";

contract StonerCats is ERC721, Ownable, ReentrancyGuard {
    using SafeMath for uint8;
    using SafeMath for uint256;
    using Strings for string;

    // Price, so we can change it if needed
    uint public PRICE = 0.35 ether;
    // Max transaction limit, so we can change it it needed
    uint public MAX_TRANS_AMOUNT = 20;
    // Max NFTs total. Due to burning this won't be the max tokenId
    uint public constant MAX_TOKENS = 13420;
    // Max at launch before ltd edition chars unlock
    uint public constant MAX_TOKENS_INIT = 10420;
    // Track current supply cap in range [MAX_TOKENS_INIT, MAX_TOKENS]
    uint internal CURR_SUPPLY_CAP = MAX_TOKENS_INIT;

    // Allow for starting/pausing sale
    bool public hasSaleStarted = false;

    // Effectively a UUID. Only increments to avoid collisions
    // possible if we were reusing token IDs
    uint internal nextTokenId = 0;

    /*
     * Set up the basics
     *
     * @dev It will NOT be ready to start sale immediately upon deploy
     */
    constructor(string memory baseURI) ERC721("Stoner Cats","TOKEn") {
        setBaseURI(baseURI);
    }

    /*
     * Get the tokens owned by _owner
     */
    function tokensOfOwner(address _owner) external view returns(uint256[] memory ) {
        uint256 tokenCount = balanceOf(_owner);
        if (tokenCount == 0) {
            // Return an empty array
            return new uint256[](0);
        } else {
            uint256[] memory result = new uint256[](tokenCount);
            uint256 index;
            for (index = 0; index < tokenCount; index++) {
                result[index] = tokenOfOwnerByIndex(_owner, index);
            }
            return result;
        }
    }

    /*
     * Main function for the NFT sale
     *
     * Prerequisites
     *  - Not at max supply
     *  - Sale has started
     */
    function mewnt(uint256 numTokens) external payable nonReentrant {
        // Save users gas
        // - only call totalSupply once
        uint256 supply = totalSupply();
        require( hasSaleStarted == true,                    "Sale paused" );
        // Save users gas
        // - no one will be dumb enough to mint 0
        require( num <= MAX_TRANS_AMOUNT,                   "Exceeds max transaction value" );
        // Save users gas
        // - no need for totalSupply() < CURR_SUPPLY_CAP when you have to following
        require( supply + numTokens <= CURR_SUPPLY_CAP,     "Exceeds maximum Cats supply" );
        // Save users gas
        // - no need for safeMaths with something so simple
        // - no need for the price function
        require( msg.value >= PRICE * num,                  "Ether sent is not correct" );

        // Cleaned up loop
        // - uint i defaults to 0
        for (uint i; i < numTokens; i++) {
            uint mintId = nextTokenId++;
            _safeMint(msg.sender, mintId);
            _setTokenURI(mintId, Strings.strConcat(Strings.uint2str(mintId), "/index.json"));
        }
    }

    /*
     * Only valid before the sales starts, for giveaways/team thank you's
     */
    function reserveGiveaway(uint256 numTokens) public onlyOwner {
        // Save users gas
        // - only call totalSupply once
        uint256 currentSupply = totalSupply();
        // Save users gas
        // - with a magic number you dont need <=, just up the value by 1
        require( currentSupply + numTokens < 101,           "Exceeded giveaway supply" );
        require( hasSaleStarted == false,                   "Sale has already started" );

        // Cleaned up loop
        // - no need for uint index, just add it to the the for loop
        // Reserved for people who helped this project and giveaways
        for (uint index; index < numTokens; index++) {
            nextTokenId++;
            _safeMint(owner(), currentSupply + index);
            _setTokenURI(currentSupply + index,
                Strings.strConcat(Strings.uint2str(currentSupply + index), "/index.json"));
        }
    }

    /**
     * @dev See {IERC165-supportsInterface}.
     */
    function supportsInterface(bytes4 interfaceId) public view override(ERC165) returns (bool) {
        return ERC165.supportsInterface(interfaceId);
    }


    // Admin functions

    /*
     * @dev Under the max of 13420, new characters from future episodes may
     * get their own tokens. This makes room for those new ones,
     * but still cannot go past the supply cap.
     */
    function addCharacter(uint numTokens) public onlyOwner {
        require(CURR_SUPPLY_CAP + numTokens <= MAX_TOKENS,
            "Can't add new character NFTs. Would exceed MAX_TOKENS");

        CURR_SUPPLY_CAP = CURR_SUPPLY_CAP + numTokens;
    }

    function getCurrentSupplyCap() public view returns(uint) {
        return CURR_SUPPLY_CAP;
    }

    function setBaseURI(string memory baseURI) public onlyOwner {
        _setBaseURI(baseURI);
    }

    // Simplified to a single function
    function hasSaleStarted(bool value) public onlyOwner {
        hasSaleStarted = value;
    }

    function setPrice(uint newPrice) public onlyOwner {
        PRICE = newPrice;
    }

    function setMaxTransAmount(uint newAmount) public onlyOwner {
        MAX_TRANS_AMOUNT = newAmount;
    }

    function withdrawAll() public payable onlyOwner {
        require(payable(msg.sender).send(address(this).balance));
    }
}