// SPDX-License-Identifier: MIT pragma solidity ^0.7.1; contract Fallback { mapping(address => uint) public contributions; address public owner; constructor() { owner = msg.sender; contributions[msg.sender] = 1000 * (1 ether); } modifier onlyOwner { require( msg.sender == owner, "caller is not the owner" ); _; } function contribute() public payable { require(msg.value < 0.001 ether); contributions[msg.sender] += msg.value; if(contributions[msg.sender] > contributions[owner]) { owner = msg.sender; } } function getContribution() public view returns (uint) { return contributions[msg.sender]; } function withdraw() public onlyOwner { payable(owner).transfer(address(this).balance); } receive() external payable { require(msg.value > 0 && contributions[msg.sender] > 0); owner = msg.sender; } } 0.7.1