Wonderturf, an artificial turf, is sensitive to the activity of people using it. It is able to distinguish whether the person just wanders around, or plays, for example, soccer. When a person or a group of people walks onto the turf, a body of light welcomes them and playfully moves along. The body invites the person actively to use the turf. For a group of people it might create a private space in which they can have a lazy afternoon. It can also invite or support play by providing appropriate lining for their ball game.