Ryūkyū (sometimes known as Ryu Kyu, or Ryuu Kyuu, and later known outside of Japan as Solitaire Poker) is a card-based puzzle game developed by ASCII and published by Login Soft for NEC PC-9801 and Sharp X68000 computers exclusively in Japan on August 1989. It was also released for the MSX (also exclusively in Japan) sometime in 1989.
In Ryuu Kyuu, players are given a 5x5 grid and four stacks of standard playing cards, where only the topmost card of each stack can be drawn (and only the top three cards of each stack are visible). Players have to choose which card to draw and which column of the grid to drop the card into, earning points based on the standard poker hand value of each row (5 in total), each column (5 in total), and both center diagonals (2 in total).
All 12 hand values are added up at the end of each stage to determine the player's score and, if they pass the threshold, they move onto the next stage. In most versions of the game, completing stages reveals more of a picture between rounds, with the goal being to reveal the complete picture. As the game is named for the Ryukyu Islands, the game has a theme that is both tropical and traditionally Japanese.
The game was later ported to arcades by Success on October 1990. Released exclusively in Japan by Sega, it ran on Sega System 16 hardware. The game was also ported to the PC Engine by Sankindo (and released by FACE exclusively in Japan on October 26, 1990). The PC Engine version was later ported to the Sega Game Gear on May 31, 1991, which was also released outside of Japan as Solitaire Poker. The Game Gear version supports linked multiplayer via the Gear-to-Gear Cable.
FACE's Hany character, from Hany in the Sky and Hany on the Road, makes a brief cameo during the PC Engine version's intro.