Please press "Leave" before leaving. It will help the game and the UNO! community. Also, to keep the game going, wait until the next person has started the countdown before leaving. Otherwise all play will stop. If you click Leave or End, don't click anything but the green flag if you want to join. No other buttons.
If you click "End", that will end the game and force the current players to rejoin. If you want to leave but someone joined after you, end the game. Otherwise the game will glitch. Two timers may be shown, but only at the start of a game.
