/// @return The balance of the user after the deposit is made
function deposit() public payable returns (uint) {
    // Use 'require' to test user inputs, 'assert' for internal invariants
    // Here we are making sure that there isn't an overflow issue
    require((balances[msg.sender] + msg.value) >= balances[msg.sender]);

    balances[msg.sender] += msg.value;
    // no "this." or "self." required with state variable
    // all values set to data type's initial value by default

    LogDepositMade(msg.sender, msg.value); // fire event

    return balances[msg.sender];
}