PROGRAMMING CHALLENGE: When the gravestone is clicked, a ghost arises from the grave, gets bigger, and flies off the screen. Constraints: 1. The ghost should increase in size as it flies across the screen. 2. When the animation is completed, it should be able to be restarted by clicking on the gravestone. EXTENSION CHALLENGE: Once the animation has started, additional clicks on the gravestone don't affect it until it's finished.
