With the seemingly unending popularity of Tetris, it's no surprise that some think there's something special about the classic that makes it hook into players' minds. The BBC has published a report exploring that psychological hook: apparently it's the game's ability to continually provide a new frustrating piece to deal with followed by the gratification of putting a piece in the right spot that's so appealing. In psychology it's related to the Zeigarnik Effect, which refers to the mind's ability to better recall incomplete tasks — and therefore hunger to complete them — but the catchy music doesn't hurt, either.