There will be more data and proper atribution here (original author, steam link, original post date, etc) real soon, I promise. This is just like a technical test to see if they're coming in ok at all.
Waves » Trading Cards Now Available
It’s a long time coming but Trading Cards didn’t even exist on Steam when the game launched back in 2011.
Check your inventory if you already own the game as you have probably already gotten your drops based on playtime you’ve already racked up.
This is a Steam update only and there are no changes to the game associated with it.