Each steam-trading-cards-enabled game has a certain number of cards that are automatically earned just by spending time playing the game. (3-5 from what I've seen so far) What I haven't been able to figure out is, how long does this take?
How many minutes do I have to spend playing each game before I earn the first (and second, third, etc) card drop? Is it randomized or fixed? Are they the same for every game?