Particalsystem.pde

class Firework {

  ArrayList<Particle> particles;
  Particle firework;
  float hu;

  Firework() {
    hu = random(270, 330); 
    firework = new Particle(random(width), height, hu);
    particles = new ArrayList<Particle>(); 
  }

  boolean done() {
    if (firework == null && particles.isEmpty()) {
      return true;
    } else {
      return false;
    }
  }

  void run() {
    if (firework != null) {
      fill(hu, 255, 255);
      firework.applyForce(gravity);
      firework.update();
      firework.display();

      if (firework.explode()) {
        for (int i = 0; i < 100; i++) {
          particles.add(new Particle(firework.location, hu));  
        }
        firework = null;
      }
    }

    for (int i = particles.size() - 1; i >= 0; i--) {
      Particle p = particles.get(i);
      p.applyForce(gravity);
      p.run();
      if (p.isDead()) {
        particles.remove(i);
      }
    }
  }
}