Divided Ranks

Rules summary

Goal

Draft 10 cards and divide them into two five-card poker hands. Whoever holds the single weakest hand at the table loses.

Cards

Use 21 cards: the 10, J, Q, K, and A of each suit, and 1 Joker. What the Joker can do is set out under Hand rankings.

Setup

Deal 1 card face down as the reserve. Nobody looks at it. The other 20 cards are the stock.

Play

Split. Each round one player is the splitter. The splitter takes the top 4 cards of the stock, looks at them, and divides them into two pairs. One pair is offered face up and the other face down.
Choose. The other player takes either pair into their hand: the face-up pair or the face-down pair without seeing it first. The splitter takes the other pair.
Five rounds. The splitter changes every round. After 5 rounds the stock is used up and each player holds 10 cards. One player has split 3 rounds and the other 2.
The reserve. Each player in turn may swap one card from their hand for the reserve, or keep their hand. The player who split only 2 rounds goes first. The swap is blind. You give up a card you choose and take the reserve without seeing it first, and your card goes face down as the new reserve. So the second player swaps with whatever the first player left there.
Build. Both players divide their 10 cards in secret into two five-card poker hands, using every card, and then show them. Each player’s lower hand is their weaker hand and the other is their stronger hand.

Scoring

Compare the players’ hands in this order, and stop at the first difference:

the category of each weaker hand, such as a full house or a straight;
the category of each stronger hand;
the two weaker hands in full, card for card;
the two stronger hands in full.

The player who comes out lower loses. So if both weaker hands are full houses, a stronger hand of four of a kind beats a stronger full house, even when its owner has the lower weaker full house. If all four steps are equal, the game is drawn.

Hand rankings

With only the 10 to the Ace in the pack, some hands work out differently:

The only straight is 10, J, Q, K, A.
Five cards of one suit are always the 10 to the Ace, so every flush is a royal flush.
Five cards with no pair are always a straight, so a hand is never just a high card.

These are the hands this pack can make, strongest first.

Royal Flush 10, J, Q, K, and A, all one suit
Four of a Kind 4 cards of one rank
Full House 3 cards of one rank and 2 of another
Straight 10, J, Q, K, and A, not all one suit
Three of a Kind 3 cards of one rank
Two Pair 2 cards of one rank and 2 of another
Pair 2 cards of one rank

The Joker is wild only for a straight or a royal flush. Anywhere else it counts below a 10, so it never makes a pair, three of a kind, four of a kind, or full house. Between two otherwise equal hands, the one without the Joker wins. Here it’s the missing Jack of a straight:

Variants

Face-up swap. Every swap at the reserve is made face up, so both players see the card given and the card taken. The first player still swaps without seeing the reserve. If they swap, the second player can see exactly which card is on offer.

Open the rules page

What you’re allowed to know

The pack is small and closed, so nearly everything is knowable if you’re paying attention. Rather than make that a memory test, the game keeps the books for you:

Your hand marks every card your opponent has watched arrive: the ones they can count on you holding.
What you know about their hand shows the faces you have seen and a back for every card you haven’t.
Unaccounted for names every card whose whereabouts you can’t pin down, and says what they could be.

Where the information comes from is worth understanding, because it’s the heart of the split: the splitter sees all four cards, so they always learn the two that go across the table. You only learn what the splitter kept by taking the hidden pair: take the visible pair and they walk off with two cards you have never seen.

And one piece of arithmetic worth carrying to the end: twenty-one cards are ten, ten and the reserve. So once the pack is spent, all but one of the cards you can’t place is in your opponent's hand: you can narrow their holding to eleven candidates and no further, because the odd one out is the reserve and nothing tells you which. That last unknown is what your blind swap is a bet on, and the panel shows you the exact odds.

Prototype notes (what the numbers say)

Divided Ranks is a prototype, and these came out of a few hundred Expert-versus-Expert games:

The bottom of the poker ladder is unreachable. With only five ranks, five cards with no pair are a straight, so "high card" can’t happen and a bare pair never did. The weakest hand at the table is a straight or a full house three times in four, and both players land in the same category more than a third of the time, which puts a lot of games on a single kicker.
The draft is dead even, and the first reserve turn is the only real asymmetry. With the reserve turn assigned by a coin flip so the two could be told apart, three splits and three choices are worth the same (50.3% over 450 games): the chooser takes the better of two pairs, the splitter sees all four cards, and it cancels. But whoever goes FIRST at the reserve wins about 59% under a blind swap, because the second player draws whatever the first one threw away: a card somebody deliberately rejected. Neither order balances the game; this one is used because it’s the literal reading of the rules.
Face up cuts that in half. With the "Face up" swap option the first turn is worth +5 instead of +9, because the second player can see the card and only takes it when it helps: they improve their weakest hand 87% of the times they swap, against the first player's 67%. The cost is that the reserve stops being a gamble for them at all.
And it’s entirely a skill effect. Between two Skilled bots the reserve order makes no measurable difference at all. It only bites once both players are good at picking which card to throw away: the better the first player is at spotting junk, the worse the second player's blind draw.
Scoring on categories first pulled most games off the kickers. Comparing the weakest hand's category, then the best hand's category, then the hands themselves, settles 83% of games on shape alone; only 15% come down to a card-for-card comparison. Under a rule that compared the weakest hands in full first, every one of the 32% of games where both weakest hands share a category went to a kicker.
A flush is a royal flush. Each suit holds exactly five cards, so any flush is the whole suit: which makes "flush" the second-best hand in the game rather than a middling one.
Concentration beats balance, which isn’t the intuition the cards suggest. Two of every rank makes two straights; three aces, three kings and two each of two more ranks makes two full houses, and four aces with four kings makes two lots of four of a kind.
Dividing the ten cards is a solved puzzle, not a decision: there are 126 ways to do it and exactly one is best, which is why Auto-arrange can always find it.
Swapping is right about three times in four, which is more often than a blind gamble sounds like it should be: with only five ranks most ten-card holdings have one card doing no work, and almost anything is an upgrade on it.

Divided Ranks

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Goal

Cards

Setup

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Scoring

Hand rankings

Variants

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Setup

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Variants

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