The Ktarian game is a one player device worn over the ears and using a visual interface. The game displays a grid pattern on which the player has to direct hovering disks into cone shaped objects over the course of multiple levels.
In 2368, Etana Jol introduced it to William T. Riker, while he was vacationing on Risa, who then helped spread it aboard the USS Enterprise-D en route for the Phoenix Cluster for the purpose of gaining control of Starfleet.
Wesley Crusher and Robin Lefler analyzed the game using a computer aboard the USS Enterprise and found that it rewards a player's successful attempt by stimulating the pleasure center of the brain creating a psychotropic addiction affecting higher reasoning and rendering that player completely submissive.
Data used an optical burst from a modified palm beacon to counter the effect of the device on the bridge crew. (TNG: "The Game")