Flash USDT (fUSDT)

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

contract SimpleFlashUSDT {
    string public name = "Flash USDT";
    string public symbol = "fUSDT";
    uint8 public decimals;
    uint256 public totalSupply;

    address public owner;
    bool public paused;

    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) public allowance;

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    event Mint(address indexed to, uint256 value);
    event Burn(address indexed from, uint256 value);
    event Paused();
    event Unpaused();

    modifier onlyOwner() {
        require(msg.sender == owner, "Not owner");
        _;
    }

    modifier whenNotPaused() {
        require(!paused, "Paused");
        _;
    }

    constructor(uint8 _decimals, uint256 initialSupply) {
        owner = msg.sender;
        decimals = _decimals;
        _mint(msg.sender, initialSupply);
    }

    function transfer(address to, uint256 amount) external whenNotPaused returns (bool) {
        require(balanceOf[msg.sender] >= amount, "Insufficient");
        balanceOf[msg.sender] -= amount;
        balanceOf[to] += amount;
        emit Transfer(msg.sender, to, amount);
        return true;
    }

    function approve(address spender, uint256 amount) external whenNotPaused returns (bool) {
        allowance[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(address from, address to, uint256 amount) external whenNotPaused returns (bool) {
        require(balanceOf[from] >= amount, "Insufficient");
        require(allowance[from][msg.sender] >= amount, "Not allowed");
        balanceOf[from] -= amount;
        balanceOf[to] += amount;
        allowance[from][msg.sender] -= amount;
        emit Transfer(from, to, amount);
        return true;
    }

    function mint(address to, uint256 amount) external onlyOwner whenNotPaused {
        _mint(to, amount);
    }

    function burn(address from, uint256 amount) external onlyOwner whenNotPaused {
        require(balanceOf[from] >= amount, "Insufficient");
        balanceOf[from] -= amount;
        totalSupply -= amount;
        emit Burn(from, amount);
        emit Transfer(from, address(0), amount);
    }

    function pause() external onlyOwner {
        paused = true;
        emit Paused();
    }

    function unpause() external onlyOwner {
        paused = false;
        emit Unpaused();
    }

    function _mint(address to, uint256 amount) internal {
        require(to != address(0), "Zero address");
        balanceOf[to] += amount;
        totalSupply += amount;
        emit Mint(to, amount);
        emit Transfer(address(0), to, amount);
    }
}