Valve has introduced a card game to Steam called Steam Trading Cards.

Steam Trading Cards are a kind of reward system. Players collect and earn virtual cards as they play through participating games on Valve’s service. Valve says about half of a game’s “deck” will drop in an average play-through, while the other half will be unlocked through trading with others.

“For example, Half-Life 2 has 8 cards in its set, you can receive 4 card drops by playing it,” writes Valve in its FAQ. “You'll need to collect the other half of the set from other community members.”

As players build “decks” they’ll earn badges, and “marketable” items such as emoticons, profile backgrounds, and coupons, says Valve. Coupons can include 50 per cent discounts on games, and DLC packs.

All badges will also have an XP value attached, and as players increase their Steam level, they’ll earn non-tradeable items such as profile showcases, and extra friend slots.

Currently, cards only drop based on how much time players have spent playing any participating game.

“We will definitely look into adding more rules for how cards are dropped in the future, but there are a few problems with in-game achievements that prevented us from using them right now,” says Valve. “Many games have achievements that are grindy or un-fun to get, and we want the act of getting game cards to be fun for all users in games.”

Steam Trading Cards will move out of beta at 7am Thursday morning NZST.