The idea is to have a box, which contains a number of objects. When the cursor is located inside the box, then we want to apply a scale and alpha value to each object dependent on the distance between each object and the cursor. On the other hand, when the mouse is located outside the box, we want each object to return to its original state.
The author wrote this tutorial to explain the infamous effect originally created by Joshua Davis of www.praystation.com. The tutorial was written with his personal permission and the source is simply a modification of the file available at PrayStation.com.