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Best
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Japanese flower cards. Match by month, build yaku, then choose: bank your points or call koi-koi for more.
Hanafuda is a deck of forty eight Japanese flower cards, twelve months of four cards each. Cards match only by month, so the large number printed on every card is the only thing you have to read. The colour tells you what the card is worth: gold for brights, green for animals, red or blue for ribbons, and plain slate for chaff.
On your turn, tap a card in your hand. If a card on the table shares its month, you capture both. If nothing matches, your card stays on the table for later. Then the top card of the deck is flipped and matched the same way. When two table cards share the month, you choose which one to take, and when three share it you sweep all four.
Captured cards form yaku, the scoring sets. Three brights are worth five, the boar, deer and butterfly together are worth five, the three red poem ribbons are worth five, five animals are worth one with a point for every extra, and ten chaff work the same way. The panel under the table shows every yaku you currently hold and its value.
The moment you complete a yaku or make an existing one bigger, the round stops and you choose. Stop banks your points and ends the round. Koi-koi keeps the round alive for a bigger hand, and doubles your score if you go on to win. The risk is real: if the rival completes a yaku first and stops, you score nothing at all, and their score is doubled because you were the one who called. A match is six rounds, and your final score is your total minus the rival's.
The whole game turns on one number: how many cards of a month are still unseen. Each month has exactly four cards. If you hold two of March and a third is face up on the table, the fourth is the only one that can ever take your pair away, and you can play the pair safely. The reverse matters more — never drop a lone valuable card onto the table when its month is still wide open, because the rival takes it for free on their next turn.
The cheapest yaku are the ones to aim at first. Ten chaff is worth one point and there are twenty four chaff in the deck, so it arrives almost by itself if you take chaff whenever nothing better is on offer. Five ribbons is the same. Those small yaku are not worth much on their own, but they are what gives you the option to stop, and the option to stop is what makes koi-koi safe to call later.
September's sake cup is the most valuable single card in the deck, because it makes a five point yaku with March's curtain and another with August's moon. If either bright is already in your captures, the cup is worth chasing hard, and if the rival holds a bright you should take the cup purely to deny them. The same logic applies to the boar, deer and butterfly: three ordinary looking animals that are worth five together.
Call koi-koi when your points are small and your hand is long, and stop when either of those stops being true. With one or two cards left you have almost no chance to improve, so calling is close to a pure gift. Watch the rival's captured counts as well: if they already show three ribbons or four animals, they are one card from a yaku of their own, and stopping with three points beats losing six.