Theta is a puzzle solving videogame released only in Japan that features two puzzles called "Kaiten Puzzle" and "Aquarium Puzzle". In the first one the player spins the theta-shaped wheels to move the colored spheres to the right place of the same color. In the second one the player moves the colored spheres inside the right vortex to make them disappear according to the image on the upper screen, trying not to be interrupted by other spheres of different colors attracted by the vortex.