// SPDX-License-Identifier: MIT
pragma solidity ^0.5.16;

contract ERC20 {
    string public name;
    string public symbol;
    uint8 public decimals;
    uint256 public totalSupply;

    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);

    constructor(
        string memory _name,
        string memory _symbol,
        uint8 _decimals,
        uint256 _initialSupply
    ) public {
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
        totalSupply = _initialSupply * 10 ** uint256(decimals);
        balanceOf[msg.sender] = totalSupply;
        emit Transfer(address(0), msg.sender, totalSupply);
    }

    function transfer(address _to, uint256 _value) public returns (bool) {
        _transfer(msg.sender, _to, _value);
        return true;
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        require(_value <= allowance[_from][msg.sender], "Insufficient allowance");
        allowance[_from][msg.sender] = allowance[_from][msg.sender] - _value;
        _transfer(_from, _to, _value);
        return true;
    }

    function approve(address _spender, uint256 _value) public returns (bool) {
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function _transfer(address _from, address _to, uint256 _value) internal {
        require(_from != address(0), "Invalid sender address");
        require(_to != address(0), "Invalid recipient address");
        require(balanceOf[_from] >= _value, "Insufficient balance");

        balanceOf[_from] = balanceOf[_from] - _value;
        balanceOf[_to] = balanceOf[_to] + _value;
        emit Transfer(_from, _to, _value);
    }
}

{
  "compilationTarget": {
    "BLX.sol": "ERC20"
  },
  "evmVersion": "istanbul",
  "libraries": {},
  "optimizer": {
    "enabled": true,
    "runs": 200
  },
  "remappings": []
}