private void SendEnterRoom()
    {
        errorText.text = "";

        bool validRoomTokenField = roomTokenInputField.text.Length != 0;

        if (validRoomTokenField)
        {
            UInt64 roomToken = Convert.ToUInt64(roomTokenInputField.text);

            gameSystem.EnteringRoomScreen(username, roomToken);
        }
        else
        {
            errorText.text += roomTokenErrorText + "\n";
        }
    }