I didn't dive too far into it but are the cards one-time use? Or do you just collect them and can use them in any game you want?
I was told to "build a deck" and stuffed like every card I had into a "deck" and still had slots left over which seemed...excessive? But then started thinking maybe I burned all those forever.
To my understanding, cards are basically perks that are randomly drawn each round, you select them and they become active until the campaign is completed. Or so I think.