Simple Deposit Account (v0.1.3 Don't Use - Intro Version for Safety Discussion)

deposit-account-0-1-3

pragma solidity >=0.4.22 <0.6.0;
contract DepositAccount {
    address private owner;
    
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }
    
    modifier withMinBalance(uint256 amount) {
        require(address(this).balance >= amount);
        _;
    }

    constructor() public {
        owner = msg.sender;
    }
    
    function withdraw() onlyOwner public {
        msg.sender.transfer(address(this).balance);
    }
    
    function withdraw(uint256 amount) onlyOwner withMinBalance(amount) public {
        msg.sender.transfer(amount);
    }
    
    function() payable external {}
}