An archetypal smiley face blinks, looks at viewers, and smiles only when no one is looking directly at it. Viewers get a glimpse of the smile as they look away, but when they look back the smiley no longer smiles. The piece is mounted on a gallery window and can be seen from both sides, but interacts only with visitors outside the gallery.
As much as viewers are looking at the piece, the piece is looking at them, and by smiling only when no one is looking, the piece is disdainful of the viewer's participation. It asks, "why are you looking at me," when of course, without viewers the piece wouldn't exist.
There are two ways to view this piece. From outside the gallery, viewers interact directly with the smiley face. From inside, viewers watch this interaction between the computer and the outside viewers.