gorgos

pragma solidity 0.6.6;
pragma experimental ABIEncoderV2;

import "https://github.com/Uniswap/uniswap-v2-core/blob/master/contracts/interfaces/IUniswapV2Pair.sol";
import "https://github.com/Uniswap/uniswap-lib/blob/master/contracts/libraries/FixedPoint.sol";
import "https://github.com/Uniswap/uniswap-lib/blob/master/contracts/libraries/FullMath.sol";
import "https://github.com/Uniswap/uniswap-lib/blob/master/contracts/libraries/Babylonian.sol";
import "https://github.com/Uniswap/uniswap-lib/blob/master/contracts/libraries/BitMath.sol";

library SafeMath {

gorgos

// SPDX-License-Identifier: MIT
pragma solidity ^0.7.4;

interface IERC20 {
    function balanceOf(address owner) external view returns (uint256);
    function approve(address spender, uint256 amount) external returns (bool);
    function transfer(address to, uint256 amount) external returns (bool);
    function transferFrom(address from, address to, uint256 amount) external returns (bool);
}

gorgos

// SPDX-License-Identifier: MIT
pragma solidity 0.7.2;

interface PoolInterface {
    function swapExactAmountIn(address, uint, address, uint, uint) external returns (uint, uint);
    function swapExactAmountOut(address, uint, address, uint, uint) external returns (uint, uint);
}

interface TokenInterface {
    function balanceOf(address) external returns (uint);

gorgos

// SPDX-License-Identifier: MIT
pragma solidity 0.6.10;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/Ownable.sol";

interface ExternalContractInterface {
    function game() external returns(ExtCodeHashExample);
    function payoutToWinner(address winner) external;
    function withdrawTo(uint roundId, address receiver) external;
    receive() external payable;

gorgos

mapping (address => uint256) gameWeiValues;
mapping (address => uint256) blockHashesToBeUsed;

function playGame() public {
    if (!blockHashesToBeUsed[msg.sender]) {
        // first run, determine block hash to be used                          
        blockHashesToBeUsed[msg.sender] = block.number + 2; // use 2 or more
        gameWeiValues[msg.sender] = msg.value;
        return;
    }