ethereumLife

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

interface IERC20 {
    function totalSupply() external view returns (uint256);
    function balanceOf(address account) external view returns (uint256);
    function transfer(address to, 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 from, address to, 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 ethereumLife is IERC20 {
    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;
    
    uint256 private _totalSupply = 21000000000000000000000000;
    string public name = unicode"以太坊人生";
    string public symbol = unicode"以太坊人生";
    uint8 public decimals = 18;
    
    constructor() {
        _balances[msg.sender] = _totalSupply;
        emit Transfer(address(0), msg.sender, _totalSupply);
    }
    
    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }
    
    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }
    
    function transfer(address to, uint256 amount) public override returns (bool) {
        require(_balances[msg.sender] >= amount, "Insufficient balance");
        _balances[msg.sender] -= amount;
        _balances[to] += amount;
        emit Transfer(msg.sender, to, amount);
        return true;
    }
    
    function allowance(address owner, address spender) public view override returns (uint256) {
        return _allowances[owner][spender];
    }
    
    function approve(address spender, uint256 amount) public override returns (bool) {
        _allowances[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }
    
    function transferFrom(address from, address to, uint256 amount) public override returns (bool) {
        require(_balances[from] >= amount, "Insufficient balance");
        require(_allowances[from][msg.sender] >= amount, "Insufficient allowance");
        _balances[from] -= amount;
        _balances[to] += amount;
        _allowances[from][msg.sender] -= amount;
        emit Transfer(from, to, amount);
        return true;
    }
}