Sheer lunacy was an electronic puzzle game that was solved when the player deactivated all the lights on the sides simultaneously.
Tom Paris introduced the game to the crew of the USS Voyager in 2375. Captain Kathryn Janeway, who spent two fruitless hours trying to solve it, recalled that he was also "behind the last ship-wide craze – yo-yos."
Seven of Nine solved the game quickly by scanning it and determining that it operated on a simple fractal regression. When Paris told her that was cheating, she replied that "cheating is often more efficient". This provided inspiration for the Voyager crew to devise a strategy against the Think Tank. (VOY: "Think Tank")