TxIndexRoll.sol

// SPDX-License-Identifier: WTFPL
// Author: [email protected]

pragma solidity >=0.7.0 <0.9.0;

/**
 * @title TxIndexRoll
 * @dev Roll your place amongst the TxIndex top of your block
 */
contract TxIndexRoll {

    uint256 public number;
    uint256 public lastBlock;
    address payable public winner;

    event LOSER(address, uint256);
    event TOPPLAYER(address, uint256);
    event WINNER(address, uint256);

    /**
     * @dev Check if your tx index is the top player of your block
     */
    function roll() public payable {
        uint256 txIndex;
        require(msg.value > 0, "You got to pay to participate");
        assembly {
          txIndex := verbatim_0i_1o(hex"49")
        }
        // New block pay the previous winner!
        if (lastBlock != block.timestamp) { // https://www.youtube.com/watch?v=T_WSXXPQYeY
            lastBlock = block.timestamp; // UUID
            number = 0; // You got to revert if you are last
            if (winner != address(0x0)) { // First time contract is called?
                emit WINNER(winner, address(this).balance);
                winner.transfer(address(this).balance); // Do the reentrancy dance https://www.youtube.com/watch?v=I1188GO4p1E
            }
            if (txIndex == 0) { // First transaction of the block has the highest probability of loosing
                winner = payable(msg.sender);
                emit TOPPLAYER(winner, address(this).balance);
                return;
            }
        }
        // You are the the top player https://youtu.be/vzA7kCCBiRw?t=176
        if (txIndex > number) {
            winner = payable(msg.sender);
            number = txIndex;
            emit TOPPLAYER(winner, address(this).balance);
            return;
        }
        emit LOSER(msg.sender, address(this).balance);
    }
}