Contract Source Code:

pragma solidity ^0.4.21;

/**
 * @title SafeMath
 * @dev https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/math/SafeMath.sol
 * @dev Math operations with safety checks that throw on error
 */
library SafeMath {

    /**
    * @dev Multiplies two numbers, throws on overflow.
    */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        if (a == 0) {
            return 0;
        }
        uint256 c = a * b;
        assert(c / a == b);
        return c;
    }

    /**
    * @dev Integer division of two numbers, truncating the quotient.
    */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // assert(b > 0); // Solidity automatically throws when dividing by 0
        // uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold
        return a / b;
    }

    /**
    * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        assert(b <= a);
        return a - b;
    }

    /**
    * @dev Adds two numbers, throws on overflow.
    */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        assert(c >= a);
        return c;
    }
}

/**
 * @title Ownable
 * @dev https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/ownership/Ownable.sol
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
    address public owner;


    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(msg.sender == owner);
        _;
    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        require(newOwner != address(0));
        emit OwnershipTransferred(owner, newOwner);
        owner = newOwner;
    }

}

/**
 * @title StandardToken
 * @dev https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/contracts/token/ERC20/StandardToken.sol
 * @dev Standard ERC20 token
 */
contract StandardToken {
    using SafeMath for uint256;

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);

    mapping(address => uint256) internal balances_;
    mapping(address => mapping(address => uint256)) internal allowed_;

    uint256 internal totalSupply_;
    string public name;
    string public symbol;
    uint8 public decimals;

    /**
    * @dev total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        return totalSupply_;
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param _owner The address to query the the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address _owner) public view returns (uint256) {
        return balances_[_owner];
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed_ to a spender.
     * @param _owner address The address which owns the funds.
     * @param _spender address The address which will spend the funds.
     * @return A uint256 specifying the amount of tokens still available for the spender.
     */
    function allowance(address _owner, address _spender) public view returns (uint256) {
        return allowed_[_owner][_spender];
    }

    /**
    * @dev transfer token for a specified address
    * @param _to The address to transfer to.
    * @param _value The amount to be transferred.
    */
    function transfer(address _to, uint256 _value) public returns (bool) {
        require(_to != address(0));
        require(_value <= balances_[msg.sender]);

        balances_[msg.sender] = balances_[msg.sender].sub(_value);
        balances_[_to] = balances_[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }


    /**
     * @dev Transfer tokens from one address to another
     * @param _from address The address which you want to send tokens from
     * @param _to address The address which you want to transfer to
     * @param _value uint256 the amount of tokens to be transferred
     */
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
        require(_to != address(0));
        require(_value <= balances_[_from]);
        require(_value <= allowed_[_from][msg.sender]);

        balances_[_from] = balances_[_from].sub(_value);
        balances_[_to] = balances_[_to].add(_value);
        allowed_[_from][msg.sender] = allowed_[_from][msg.sender].sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
     *
     * Beware that changing an allowance with this method brings the risk that someone may use both the old
     * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
     * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     * @param _spender The address which will spend the funds.
     * @param _value The amount of tokens to be spent.
     */
    function approve(address _spender, uint256 _value) public returns (bool) {
        allowed_[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }
}

/**
 * @title EthTeamContract
 * @dev The team token. One token represents a team. EthTeamContract is also a ERC20 standard token.
 */
contract EthTeamContract is StandardToken, Ownable {
    event Buy(address indexed token, address indexed from, uint256 value, uint256 weiValue);
    event Sell(address indexed token, address indexed from, uint256 value, uint256 weiValue);
    event BeginGame(address indexed team1, address indexed team2, uint64 gameTime);
    event EndGame(address indexed team1, address indexed team2, uint8 gameResult);
    event ChangeStatus(address indexed team, uint8 status);

    /**
    * @dev Token price based on ETH
    */
    uint256 public price;
    /**
    * @dev status=0 buyable & sellable, user can buy or sell the token.
    * status=1 not buyable & not sellable, user cannot buy or sell the token.
    */
    uint8 public status;
    /**
    * @dev The game start time. gameTime=0 means game time is not enabled or not started.
    */
    uint64 public gameTime;
    /**
    * @dev If the time is older than FinishTime (usually one month after game).
    * The owner has permission to transfer the balance to the feeOwner.
    * The user can get back the balance using the website after this time.
    */
    uint64 public finishTime;
    /**
    * @dev The fee owner. The fee will send to this address.
    */
    address public feeOwner;
    /**
    * @dev Game opponent, gameOpponent is also a EthTeamContract.
    */
    address public gameOpponent;

    /**
    * @dev Team name and team symbol will be ERC20 token name and symbol. Token decimals will be 3.
    * Token total supply will be 0. The initial price will be 1 szabo (1000000000000 Wei)
    */
    function EthTeamContract(
        string _teamName, string _teamSymbol, address _gameOpponent, uint64 _gameTime, uint64 _finishTime, address _feeOwner
    ) public {
        name = _teamName;
        symbol = _teamSymbol;
        decimals = 3;
        totalSupply_ = 0;
        price = 1 szabo;
        gameOpponent = _gameOpponent;
        gameTime = _gameTime;
        finishTime = _finishTime;
        feeOwner = _feeOwner;
        owner = msg.sender;
    }

    /**
    * @dev Sell Or Transfer the token.
    *
    * Override ERC20 transfer token function. If the _to address is not this EthTeamContract,
    * then call the super transfer function, which will be ERC20 token transfer.
    * Otherwise, the user want to sell the token (EthTeamContract -> ETH).
    * @param _to address The address which you want to transfer/sell to
    * @param _value uint256 the amount of tokens to be transferred/sold
    */
    function transfer(address _to, uint256 _value) public returns (bool) {
        if (_to != address(this)) {
            return super.transfer(_to, _value);
        }
        // We are only allowed to sell after end of game
        require(_value <= balances_[msg.sender] && status == 0 && gameTime == 0);
        balances_[msg.sender] = balances_[msg.sender].sub(_value);
        totalSupply_ = totalSupply_.sub(_value);
        uint256 weiAmount = price.mul(_value);
        msg.sender.transfer(weiAmount);
        emit Transfer(msg.sender, _to, _value);
        emit Sell(_to, msg.sender, _value, weiAmount);
        return true;
    }

    /**
    * @dev Buy token using ETH
    * User send ETH to this EthTeamContract, then his token balance will be increased based on price.
    * The total supply will also be increased.
    */
    function() payable public {
        // We are not allowed to buy after game start
        require(status == 0 && price > 0 && gameTime > block.timestamp);
        uint256 amount = msg.value.div(price);
        balances_[msg.sender] = balances_[msg.sender].add(amount);
        totalSupply_ = totalSupply_.add(amount);
        emit Transfer(address(this), msg.sender, amount);
        emit Buy(address(this), msg.sender, amount, msg.value);
    }

    /**
    * @dev The the game status.
    *
    * status = 0 buyable & sellable, user can buy or sell the token.
    * status=1 not buyable & not sellable, user cannot buy or sell the token.
    * @param _status The game status.
    */
    function changeStatus(uint8 _status) onlyOwner public {
        require(status != _status);
        status = _status;
        emit ChangeStatus(address(this), _status);
    }

    /**
    * @dev Change the fee owner.
    *
    * @param _feeOwner The new fee owner.
    */
    function changeFeeOwner(address _feeOwner) onlyOwner public {
        require(_feeOwner != feeOwner && _feeOwner != address(0));
        feeOwner = _feeOwner;
    }

    /**
    * @dev Finish the game
    *
    * If the time is older than FinishTime (usually one month after game).
    * The owner has permission to transfer the balance to the feeOwner.
    * The user can get back the balance using the website after this time.
    */
    function finish() onlyOwner public {
        require(block.timestamp >= finishTime);
        feeOwner.transfer(address(this).balance);
    }

    /**
    * @dev Start the game
    *
    * Start a new game. Initialize game opponent, game time and status.
    * @param _gameOpponent The game opponent contract address
    * @param _gameTime The game begin time. optional
    */
    function beginGame(address _gameOpponent, uint64 _gameTime) onlyOwner public {
        require(_gameOpponent != address(this));
        // 1514764800 = 2018-01-01
        require(_gameTime == 0 || (_gameTime > 1514764800));
        gameOpponent = _gameOpponent;
        gameTime = _gameTime;
        status = 0;
        emit BeginGame(address(this), _gameOpponent, _gameTime);
    }

    /**
    * @dev End the game with game final result.
    *
    * The function only allow to be called with the lose team or the draw team with large balance.
    * We have this rule because the lose team or draw team will large balance need transfer balance to opposite side.
    * This function will also change status of opposite team by calling transferFundAndEndGame function.
    * So the function only need to be called one time for the home and away team.
    * The new price will be recalculated based on the new balance and total supply.
    *
    * Balance transfer rule:
    * 1. The rose team will transfer all balance to opposite side.
    * 2. If the game is draw, the balances of two team will go fifty-fifty.
    * 3. If game is canceled, the balance is not touched and the game states will be reset to initial states.
    * 4. The fee will be 5% of each transfer amount.
    * @param _gameOpponent The game opponent contract address
    * @param _gameResult game result. 1=lose, 2=draw, 3=cancel, 4=win (not allow)
    */
    function endGame(address _gameOpponent, uint8 _gameResult) onlyOwner public {
        require(gameOpponent != address(0) && gameOpponent == _gameOpponent);
        uint256 amount = address(this).balance;
        uint256 opAmount = gameOpponent.balance;
        require(_gameResult == 1 || (_gameResult == 2 && amount >= opAmount) || _gameResult == 3);
        EthTeamContract op = EthTeamContract(gameOpponent);
        if (_gameResult == 1) {
            // Lose
            if (amount > 0 && totalSupply_ > 0) {
                uint256 lostAmount = amount;
                // If opponent has supply
                if (op.totalSupply() > 0) {
                    // fee is 5%
                    uint256 feeAmount = lostAmount.div(20);
                    lostAmount = lostAmount.sub(feeAmount);
                    feeOwner.transfer(feeAmount);
                    op.transferFundAndEndGame.value(lostAmount)();
                } else {
                    // If opponent has not supply, then send the lose money to fee owner.
                    feeOwner.transfer(lostAmount);
                    op.transferFundAndEndGame();
                }
            } else {
                op.transferFundAndEndGame();
            }
        } else if (_gameResult == 2) {
            // Draw
            if (amount > opAmount) {
                lostAmount = amount.sub(opAmount).div(2);
                if (op.totalSupply() > 0) {
                    // fee is 5%
                    feeAmount = lostAmount.div(20);
                    lostAmount = lostAmount.sub(feeAmount);
                    feeOwner.transfer(feeAmount);
                    op.transferFundAndEndGame.value(lostAmount)();
                } else {
                    feeOwner.transfer(lostAmount);
                    op.transferFundAndEndGame();
                }
            } else if (amount == opAmount) {
                op.transferFundAndEndGame();
            } else {
                // should not happen
                revert();
            }
        } else if (_gameResult == 3) {
            //canceled
            op.transferFundAndEndGame();
        } else {
            // should not happen
            revert();
        }
        endGameInternal();
        if (totalSupply_ > 0) {
            price = address(this).balance.div(totalSupply_);
        }
        emit EndGame(address(this), _gameOpponent, _gameResult);
    }

    /**
    * @dev Reset team token states
    *
    */
    function endGameInternal() private {
        gameOpponent = address(0);
        gameTime = 0;
        status = 0;
    }

    /**
    * @dev Reset team states and recalculate the price.
    *
    * This function will be called by opponent team token after end game.
    * It accepts the ETH transfer and recalculate the new price based on
    * new balance and total supply.
    */
    function transferFundAndEndGame() payable public {
        require(gameOpponent != address(0) && gameOpponent == msg.sender);
        if (msg.value > 0 && totalSupply_ > 0) {
            price = address(this).balance.div(totalSupply_);
        }
        endGameInternal();
    }
}