So, still a few things to cover in CARDS. Namely how things works on the GMs side. Obviously since characters use an entire 54 card deck for their "hit points" they won't be going down without a lot of punishment. If each monster or NPC had their own deck things are going to get ridiculous. So, there's got to be a separate mechanic for NPCs and a fairly specific structure for games.
So, once everyone has created a character they should get a deck of cards and shuffle it and draw their first hand and the Adventure begins. The Adventure basically consists of the plot for your game. It could be an adventure of courtly intrigue tracking down hidden assassins or (more likely) a journey through a deep, dangerous dungeon to snag some loot. Essentially an Adventure is the period where things are happening, risks are taken and cards are played.
Normally a player keeps the same deck throughout an Adventure. Cards that are played or discarded are put in a separate discard pile. In many cases Adventures will be simple and can likely be resolved in a single play session but if you're running a longer term adventure then it's easy enough to separate your deck and discard with a strip of colored paper or something similar and stick it back in the box.
It's not normally possible to "heal" damage during an Adventure unless you're using a Trick or benefiting from some sort of magic item. Even if you spend the night at an inn, receive first aid or make camp in the woods you can't recover from the strain of adventuring. Full restoration (shuffling your hand and discard back into your deck) normally only happens at the end of an Adventure but for long-term adventures the GM may allow the players to restore their deck under special circumstances (blessing of a divine entity, dousing in a healing spring, a powerful artifact, etc). GMs should keep in mind that restoring a player's deck not only lets them keep going longer, but also gives them back any of the powerful face cards they may have used, making it an extremely potent gift. Don't hand that sort of thing out lightly.
When planning your adventure keep in mind that there's just about no fight a character can't win with a full deck of cards. A 1st-level warrior could probably take down a dragon in a one-on-one fight. Even low-level characters have a full range of face cards for each suit. Higher level characters have more reliability and a powerful suite of Tricks, but if you burn through all your cards in one sitting you're going to end up with a hefty dose of powerful cards before burning through all 54. And no matter how mighty they may be there is no foe who can simply strike down a PC with a full deck in a single blow. Pacing is important in this system, battles are about attrition and forcing the player to make choices about conserving their resources.
After an Adventure is over, foes are slain and the loot has been dragged back to down everyone can shuffle their cards back into their deck and start Downtime. Downtime is when XP is handed out and players have an opportunity to handle personal projects, buy equipment and kill time. You don't play cards in downtime normally, generally there shouldn't be much that would call for it. If things start happening that really need cards to be played then it should probably represent the start of a new Adventure.
NPCs and Monsters
So, if a PCs deck makes it more or less impossible for them to be taken down in a single fight, how does it work for their foes? Obviously an orcish warrior isn't going to be toting around fifty-ish cards of their own.
Instead, each NPC has 4 statistics associated with a card suit: Clubs, Diamonds, Hearts and Spades. Whenever taking an appropriate action they can automatically be considered to play a card with the appropriate rating.
Take an "average" human. They have a rating in 3 in all four categories (2 would be the equivalent of a deficient score, while 1 is practically worthless). If this guy decides to try and clock you with a chair treat his attack as a 3 of Clubs. If he tries to figure out that you're lying he is treated as playing a 3 of Diamonds, etc. Keep in mind that face cards represent immensely powerful abilities, and no one (except perhaps a powerful god) should have an Ace.
As far as taking punishment goes that depends on the opponent's Threat Level, which are as follows:
Fodder: These guys are the weakest of threats and mostly represent nameless human or humaniod monsters who hang around in gangs and are fairly worthless on their own. They generally do not have any stats above a 5 or so and any successful attack will take a Fodder character out. Fodder might have a Talent or two.
Fodder Gangs: A group of Fodder NPCs can team up to take on stronger foes. Treat a band of Fodder as a single character that attacks and defends as a unit. They have the stats of a single member of the gang, with a bonus based on the number of members. Two Fodder NPCs get a +1 to the Card Value of attacks using Clubs and this increases by +1 every time the gang doubles in size (+2 at four members, +3 at eight members, +4 at 16 members, etc.). Each point of damage inflicted on a gang kills one its members. In addition to the Talents of its members a Fodder gang may occasionally have a teamwork based Trick it can perform.
Minor Threat: A minor threat is an opponent who is not tough enough to present a significant challenge to a PC, but a group of them might make for a decent fight. They're often the leaders of a group of fodder (such as a guard captain or an orcish war-leader). Minor threats can take 5 points of damage before going down and generally have stats around 4-6 in their relevant areas. Minor threats usually have 2 or 3 Talents and may have a Trick or two.
Moderate Threats: A single moderate threat might be able to hold their own against a band of PCs for a couple of rounds. A group of them might present a real danger, especially to an exhausted team. They will usually have some stats above 5 and can take 10 damage before giving out. They will have at least 3 Talents and a small selection of Tricks.
Major Threats: Major threats are the really big opponents, dragons, giants, arch-mages, etc. These are usually the "boss battles" of an adventure. A single Major threat could easily burn through half a PCs deck before being taken down...and usually you don't face them until you're already exhausted. A group of these opponents would be suitable only for high-level players. They are likely to have around 5 or so Talents and 3-5 powerful Tricks. They can also take 20 points of damage before being taken down.
Extreme! Threats: Want to challenge your level 10 party? Well, an Extreme! threat is the way to go. These are things like gigantic dragons, titans, master liches and demi-gods. They'll have some stats at 10 or possibly higher. They'll have a selection of talents and unique Tricks as well, likely around 6 or more (although they could easily have 3-5 extremely powerful ones). Extreme! threats can take 40 damage before expiring. Keep in mind that even a threat of this magnitude can't expect to win against PCs with a full deck of cards...save them for final fights.
The DM's Deck
Obviously a monster with stats in the 3-4 range isn't going to be enjoying much success unless they're facing a particularly unlucky PC...and may not be able to act at all if things are Difficult. That's where the DM's deck comes in. The DM has a deck of cards as well that he can use to help out NPCs facing off against players. Any time an NPC takes an action or reaction the DM can play a card from his hand which replaces the monster's suit stat. If the task involved is Difficult the DM can choose to play the extra cards from his hand (or just play two or more and replace the original suit entirely).
Example: The DM is in charge of an ogre that is battling 3 PCs and has a 5 of diamonds, a 9 and a 7 of clubs, a 5 of spades and a two of hearts. The ogre has the following stats: 5C, 2D, 4H, 3S. On the monster's turn it wants to try and smash the puny warrior before finishing off his two companions. However, the warrior's player has a couple of defensive Talents and the GM is fairly sure that he'll be able to beat the ogre's automatic 5 of Clubs without a problem. So he decides to play his 7 of clubs. This replaces the ogre's score of 5 for this attack and forces the warrior to play an 8 of Hearts to successfully defend. Now it's the PCs turn. The Trickster uses a Trick in order to make the Ogre's defenses Difficult for the round and his two allies attack. The wizard is low on cards and plays a measely 3 of clubs. Normally this would be beaten by the ogre's Hearts stat easily but since this is difficult he's got to produce another card to defend. The DM decides to accept the failure and plays that 2 of hearts. That's still a failure, but only by one and the ogre takes a single point of damage.
Just like the PCs the DM will draw a hand of 5 cards at the start of the adventure and after playing any cards will draw up to 5. The DM does not "take damage" and generally only discards cards to active a monster's Tricks. If the DM's deck runs completely dry he is forced to use up the cards in his hand and once that happens he shuffles his deck back together and draws a new hand (however, the PCs get a healthy XP reward every time the DM burns through his deck, see below).
Levels and XP:
I'm still mulling over how levels and experience are handled. Here's what I've got so far:
Five XP is enough to level up until you hit level 4. That point it doubles to 10 XP per level until level 7 when it increases to 15 XP per level. Earning XP is pretty simple:
*2 XP for defeating a Major Threat, 5 for defeating an Extreme! threat.
*3 XP any time the DM refreshes their deck.
*2-4 XP for completing an Adventure, depending on length.
*1 XP for doing something amazing unrelated to any of the above.
You get 3 Talents at 1st level and you get an extra talent every odd level. I also think that at say levels 4, 7 and 10 you should get to increase the size of your hand by 1 but I haven't decided that for sure.
So, I think I'll spend some time organizing all these thoughts, maybe throw them into a pdf and playtest a little.