In uno, the timer pauses when choosing a colour. I think it would be fair to implement the same feature in 99 for 10 and Ace.

That'll take the fun out of it. Although I understand it is somewhat tricky for people with slower connection. I wish have an option like shift enter or control enter will play 11 vs 1 similary minus ten and plus.

Hello,
there is a difference between how this works in Uno and in Ninety nine:
In Uno, when you play a wild, you already put the card down, and you can't do anything else after you played it other than choose a color, so it makes sense for the timer to stop while you do so. If it doesn't stop, it leaves the game in a confusing state if your time expires. Which color should be chosen? Some random one? Annoying for everybody.
In Ninety nine, when you play an ace or a ten, nothing is yet decided, you did not even play the card until you make your choice. If the timer stops, you can use that to cheat, play an ace, wait a little to think about the current total, press Escape to cancel that and play something totally different. In fact due to the way this currently works, your opponent does not even know why the timer stopped. Of course all of that can be changed so an ace is played right away and then you make your decision, but honestly, I like the proposal by Fawaz, and it is what I was thinking about myself.
It's just that we can't use CTRL+Enter, this is used to open a link in the current message, so instead, I would say it should be left/right arrows, left arrow to play the lower/negative variant directly, so minus 10 and 1, and right arrow to play the higher/positive variant directly, plus 11 or plus 10.

The arrow system is a good idea but I think up or down arrow would be better.

I am quite curious how that would work.

YNWA just wanted to write a message it seems nothing else.
Don't get me started. You already know up and down arrows go through the cards in the list. Do we have to complicate it furthermore and change the system? :D