The whistle is an item that can be obtained by the player in the video game World of Goo. To perform this action, the player need only simply click and hold down while not selecting a Goo. Their cursor will begin to whistle, and all Goos not part of a structure will begin to move faster and toward the noise. This technique is first unlocked in Leap Hole, and is necessary to complete the level Whistler. It is first unlocked in Chapter 2, and is mandatory for many timed OCD targets found later in levels.