The game's title sounds like a psychological phenomenon — and it is, in fact, exactly that, where players start "seeing" the patterns of "Tetris" in the world or in their mind as they drift off to sleep. "Tetris Effect," the game, takes that and twists it back on itself.
During gameplay, a synaesthetic journey takes place in the background. With each twist of the "Tetris" block ("tetronimo") and lateral movement, the game's music responds in turn. While this auditory collaboration occurs, the game's background visuals take players on a journey through space, or the oceans, or across a vast desert.
It's surreal, and beautiful, and intense — and it's much more than a parlor trick.
Beyond offering an additional audio/visual component, these synaesthetic effects serve to further imprint the game's seemingly simplistic gameplay into consciousness. It deepens an already flow-like experience.