This is an example of a very simple Pen project. Click the green flag to create a new random pattern. If you look inside, you'll see three synchronized forever loops in the "Loop" broadcast handlers: Sprite1 bounces randomly across the stage and saves it's position in a list which stores the last 50 positions (x & y: 100 items in the list). Sprite2 moves to the oldest position stored in the list, thus following Sprite1 at a distance. The Pen sprite continuously change pen color slightly and draws a line between Sprite1 and Sprite2. All code by me (@kriblo).
