function balanceOfUnclaimedRaceCoin(address player) internal view returns (uint256) {
        uint256 lastSave = lastRaceCoinSaveTime[player];
        if (lastSave > 0 && lastSave < block.timestamp) {
            return (getRaceCoinProduction(player) * (block.timestamp - lastSave)) / 100;
        }
        return 0;
    }