When you run Whorld, you'll see a dialog asking if you want to view the demo. This dialog can be permanently suppressed by checking the "don't show me this again" checkbox. The demo can be viewed later, by selecting View/Demo from the main menu. To stop the demo, select View/Demo again.
During the demo, you can experiment with Whorld's effects. For example, try pressing:
Note that fill and X-Ray may cause the animation to slow down or become jerky; see performance.