One cool thing is the ability to create your own deck and the ability to share with other users.

There are a lot of existing games already in the system and plenty more shared on the reddit group: https://www.reddit.com/r/PlayingCardsIO/

Also there is an open-source clone available: https://virtualtabletop.io/

And somewhat related, /r/digitaltabletop has a huge list of options to play games online: https://www.reddit.com/r/digitaltabletop/comments/gg4sfx/big...