This interaction is the origin of the Distance Pot, which was essentially a fork of this design. The idea was to use the familiar touch screen gesture of ‘pinch to zoom’ as a ‘range type’ number input. The high degree of proprioception in the hand means that the gesture maps well to continuous adjustment and is conducive to what I call interaction fluency. Using a finger and thumb gives a strong sense of the value, as you can easily sense the distance between the fingers without having to look at them.

This makes it well suited to situations where you want the focus to be on the thing being adjusted and not the widget being used to do the adjusting. It works nicely on an peripheral (a trackpad, or phone as a controller) to adjust whichever parameter is currently selected on the primary device.

Flexibility

The gesture is so simple that it makes it possible for the user to interact with it in a number of ways: the classic pinch-to-zoom, with two hands, moving one finger while tapping the other to move in steps.

Demo

(Touch screen devices only!)

Source Code