A particle system is a system that controls particles. In our case, ParticleSystem is a class we will write that will spawn instances (lots of instances) of the Particle class (also a class we will write) that will create a simple, explosion-like effect.
Here is an image of some particles controlled by a particle system as it may appear by the end of this chapter:
Just for clarification, each of the colored squares is an instance of the Particle class and all the Particle instances are controlled and held by the ParticleSystem class. In addition, the user will create multiple (hundreds of) ParticleSystem instances by drawing with their finger. The particle systems will appear as dots or blocks until the user taps the pause button and they come to life. We will examine the code closely enough so that you will be able to amend in code the size, color, speed, and quantities of Particle and ParticleSystem instances.