Interactive  art is any type of art that involves the viewer in the creative process. The viewer becomes a user. Interactive art attempts to challenge the traditional boundary between artist and "audience". It may use a physical medium, as in the case of installation art, or it may be purely digital and Internet-based. Interactive art often employs computing power to govern responses to user actions. The art movements of the early 1900s in Europe and North America laid the groundwork for the emergence of interactive art. People began questioning the role of the artist, work, and viewer in art. French-American artist Marcel Duchamp may have created one of the first examples of interactive art with his 1920 device Rotary Glass Plates. His machine used a motor to spin rectangular pieces of glass that had segments of circles painted on them. When viewed from a distance of 3.28 feet (1 meter), an optical illusion of full circles was formed. Technology usually factors prominently in interactive art. For a work of art to be interactive, it must have some way of sensing a user's actions. This can be in the form of physical sensors or, in the case of Internet-based art, computer input devices like the mouse or touch screens. The work typically must also have a specific way of responding to inputs. Often, a large number of outcomes are possible with much room for viewer interpretation.