Parley is loosely based on the card "game" War, although the rules are changed enough to allow for a good amount of strategy. First of all, you have a choice of two cards from your hand to play. Secondly, both your active hand and your opponent's are visible when deciding which card to play, so you can maximize your chances of success. If you win the battle, you gain one Clout point as well as the card you captured, which replaces your just-played card in your active hand. Replaying this card will earn you triple Clout points if you win again, a neat way to incorporate the competition theme as well as extend the strategy beyond simply choosing the highest card in your hand. Win a match by running your opponent out of cards.
Since so much information is out in the open, strategy becomes very subtle. You will know what cards will be in your hand and your opponent's hand for at least the next two turns, so there are situations where it might be suitable to sacrifice a card in the short-term for a better overall situation. Matt and Joe have crafted a game environment rich with possibilities.
Analysis: For this single-player implementation of Parley, the AI is not all that it could be. In the earlier levels, it seems as if there is no AI at all, like the computer is choosing cards at random. Even worse, at the later levels, the computer seems to choose its card based on the card that you already played — in effect, the computer gets a sneak preview and can then select the best card based on this extra information. To offset this advantage a bit, you can spend up to three bribes in a match to steal one of your opponent's cards, at the expense of clout.
Except that clout points are, for all intents and purposes, worthless. Whether you have positive or negative clout doesn't appear to have any effect on the game whatsoever. There's no minimum clout requirement to advance to the next level; in fact there's no requirement at all. You can start out at the top castle if you want.
Since first rolling out the game during the competition, Matt has made a couple of changes to the version that is now online that addresses some of the criticisms expressed here and in the comments. In this latest version, the AI increases gradually each level (as opposed to starting strong at level 5), and at its toughest it's only half as difficult as it was before. Also, he removed the "Earth Page" card that a number of players complained about since there is nothing that it can beat and is therefore worthless. Even with these changes, however, the AI still feels like it needs to be improved.
Parley is a great card game in theory, but the single-player implementation here fails to live up to the potential of the game. If the authors can improve the AI even more, or work out a head-to-head mode, it could very well be on the verge of habit-forming. Or maybe they could sell physical Parley decks on the Web. Hmmm... Oh well. Until then, play Parley right here.
Parley is also available to play on Matt's Skeptictank website.