Token

// SPDX-License-Identifier: MIT
pragma solidity 0.8.34;

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address recipient, uint256 amount) external returns (bool);
    function allowance(address owner, address spender) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
}

contract Token is IERC20 {
    string public name;
    string public symbol;
    uint8 public constant decimals = 18;
    uint256 private constant _totalSupply = 1000000e18;

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

    constructor(string memory name_, string memory symbol_) {
        name = name_;
        symbol = symbol_;

        balanceOf[msg.sender] = _totalSupply;
        emit Transfer(address(0), msg.sender, _totalSupply);
    }

    function totalSupply() public pure override returns (uint256) {
        return _totalSupply;
    }

    function transfer(address to, uint256 amount) external returns (bool) {
        require(to != address(0), "Zero address");
        require(balanceOf[msg.sender] >= amount, "Balance too low");

        balanceOf[msg.sender] -= amount;
        balanceOf[to] += amount;

        emit Transfer(msg.sender, to, amount);
        return true;
    }

    function approve(address spender, uint256 amount) external returns (bool) {
        require(spender != address(0), "Zero address");

        allowance[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(address from, address to, uint256 amount) external returns (bool) {
        require(to != address(0), "Zero address");
        require(balanceOf[from] >= amount, "Balance too low");
        require(allowance[from][msg.sender] >= amount, "Allowance too low");

        allowance[from][msg.sender] -= amount;
        balanceOf[from] -= amount;
        balanceOf[to] += amount;

        emit Transfer(from, to, amount);
        return true;
    }
}