Koi-Koi is played with hanafuda ("flower cards"), a 48-card deck of twelve months of four cards each that emerged when Western playing cards were banned in Edo-period Japan. When you complete a scoring combination you may stop — or call "koi-koi" and gamble it all on a bigger hand.
Status
Not implemented. This game appears in the catalog and is visible in the app,
but it is marked *Coming Soon* and cannot be played.
Pending: the full yaku set and the koi-koi doubling decision deserve a dedicated implementation. The 48-card hanafuda deck itself is already modelled in the engine primitives.
We would rather show an honest placeholder than ship a rules approximation of a
game that people actually play.