solidity homework

PiggyWallet.sol

// SPDX-License-Identifer: MIT 

pragma solidity ^0.8.0;

contract PiggyWallet {
    address payable private owner;
    mapping (address => uint256) private wallet;

    function putMoney() public payable {
        wallet[msg.sender] += msg.value;
    }

    function withdrawMoney(uint256 amount) public {
        if (wallet[msg.sender] < amount) {
            revert('Not enough money');
        }
        wallet[msg.sender] -= amount;

        payable(msg.sender).transfer(amount);
    }

    function showMoney() public view returns(uint256) {
        return wallet[msg.sender];
    }
}