I’m working this week on Chapter 3 of my upcoming Nature of Code book. For the most part, if you are looking to connect particles with springs, I recommend the wonderful verlet physics of toxiclibs, and I have some examples for that here. Nevertheless, I am including an elementary implementation of a single “bob” connected to an “anchor” point via a “spring” force. The example implements Hooke’s Law (Spring Force = -k * displacement) with the PVector class, using the Euler integration model of all my other examples. Here it is below.