* Modify environment

Again this is usually superficial, but it can nonetheless create a shift in emotional and intellectual context as well as generating more involvement. Extreme Pinball [Epi97] allows the audience to select which pinball environment they wish to toss a ball around in. They can play within "Monkey Mayhem", which takes place in a zoo environment and friendly hamsters help them to gain points, or "Urban Chaos" where they face down criminals and gain points by restoring law and order to the city. The basics are the same for both games, yet the implied stories make quite a difference in how the audience experiences what they are doing, whether they laugh or feel intensely serious. I would include in environmental influence the ability to change the background music, since that significantly affects how the audience feels about the events going on. OutRun [Gam86] made clever use of this by giving the choice of tunes the car radio will play as they race down different tracks.