Simple guessing game on Solidity

GuessingGame.sol

pragma solidity ^0.4.18;

// Problem - generate a random rumber

contract GuessingGame {
    
    uint nonce = 0;
    
    event UserWon(address user, uint numberGenerated);
    event UserLost(address user, uint numberGenerated);
    
    // start with an empty payable function so users can fund the game with ETH
    function() public payable {
        
    }
    
    // get balance of contract
    function getBalance() public constant returns(uint) {
        return this.balance;
    }
    
    function playGame() public payable {
        
        // RULE 1: Users needs to pay 0.01 ETH to play
        
        // use code bellow if using JavaScript VM, comment assert
        // if(msg.value != 0.01 ether) {
        //     throw;
        // }
        // use if using Injected Web3
        assert(msg.value == 0.01 ether);
        
        // generate a random number by getting the block No
        uint randomNumber = uint(keccak256(block.blockhash(block.number), nonce)) % 100;
        nonce++;
        
        // RULE 2: User gets 0.02 back if number is even
        if(randomNumber % 2 == 0) {
            // even, send the user 0.02 ether
            msg.sender.transfer(msg.value * 2);
            UserWon(msg.sender, randomNumber);
        } else {
            // odd
            UserLost(msg.sender, randomNumber);
        }
    }
}