Koi-Koi

Koi-Koi (こいこい) is a two-player hanafuda game. Capture cards of the same month, build the four scoring piles, and decide whether to Stop or call Koi-Koi and play on.

The deck is the 48 traditional hanafuda cards, four for each month. There are no bonus cards. Each card belongs to one month and one kind:

The Sake Cup is an animal, and it also counts as one chaff.

Months follow the Japanese order. Paulownia, with the Phoenix, is December. Willow, with the Rain Man, the swallow, a plain ribbon, and the lightning chaff, is November. A card's face shows its month numeral. The plant name appears when you inspect the card.

The first dealer is chosen at random. After that, the player who scored the round deals the next one. A drawn round keeps the same dealer.

Cards are dealt two at a time: two to the opponent, two face up to the table, two to the dealer, repeated until each player has 8 and the table has 8. The remaining 24 cards are the stock.

If the table is showing all four cards of one month, the cards are gathered and dealt again. That redeal does not count as a round. Three of one month on the table is legal and stays.

Lucky hands are a lobby option, off by default. Before play, a hand of four of one month (teshi) or four different months of two cards each (kuttsuki) wins the round for 6 points. There is no doubling. That player deals next.

If both players hold a lucky hand, the round is drawn, it counts as played, and the same dealer deals again.

On your turn, play one card from your hand, then flip the top card of the stock.

Capture is compulsory. A card you just played to the table can be matched by the stock card you flip immediately afterwards.

Captured cards are sorted into Brights, Animals, Ribbons, and Chaff.

Only captured cards score. Bright yaku do not stack with each other. Every other yaku stacks.

Three brights that include the Rain Man score no brights yaku. Moon Viewing and Flower Viewing can still score beside them, and they can score together.

There is no red-ribbon yaku. The willow ribbon is an ordinary ribbon.

The tracker beside your captures shows a completed yaku with its points, and an unfinished one as progress, such as Boar-Deer-Butterfly 2/3. The chaff count includes the Sake Cup.

At the end of your turn, after the stock card is resolved, you may Stop or call Koi-Koi when your yaku total is higher than it was at your last decision this round.

Stop ends the round. Your points are your yaku total. If that total is 7 or more, it is doubled. If your opponent has called Koi-Koi this round, it is doubled again. Your own Koi-Koi calls never change your own score. The opponent scores nothing for the round.

Koi-Koi keeps the round going. A later rise in your yaku asks you again. Both players may call. Whoever stops first wins the round, and that player deals next.

If the rise happens on the turn that empties your hand, you Stop automatically. There is no prompt. The same doublings apply, including your opponent's Koi-Koi.

The dealer runs out of cards one turn before the other player. The round does not end just because the dealer is out, unless the dealer stops.

A Koi-Koi call stays marked on that player for the rest of the round.

If both hands are empty and nobody has stopped, the round is scored from the last Koi-Koi call:

The stock never runs out before the hands do. Sixteen cards are drawn during play, and eight stay unused.

A drawn round counts toward the match.

A match is 12 rounds, or 6 if that lobby option is chosen. Each round's points add to the match score. The higher total wins. Equal totals draw the match.

The hwatu card faces are used under CC BY-SA 4.0 — by Spenĉjo (Wikimedia Commons), from work by Marcus Richert, based on hanafuda graphics by Louie Mantia, Jr. Full credits are in the hwatu-deck package README. The card back is original Gameweave artwork.