class SmokeLayer extends Layer {
  ParticleSystem system;
  Particle last;
  int smokeAmount = 12;
  int smokeSize = 15;

  SmokeLayer(PApplet parent) {
    super(parent);
  }

  void setup() {
    fill(255, 64);
    system = new ParticleSystem(-0.1f, 0.001f);
    ellipseMode(LaserBurn.CENTER);
    smooth();
  }

  void draw() {
    background(0, 0);
    noStroke();

    int dx = (int)(random(-5, 5));
    int dy = (int)(random(-5, 5));
    if (mousePressed) {
      for (int i = 0; i < smokeAmount; i++) {
        Particle p = system.makeParticle(1.0f, mouseX + dx, mouseY + dy, 0);
        p.velocity().set(random(-1, 1), random(-2, -5), 0);
        if (last != null)
          system.makeSpring(p, last, 0.1f, 0.1f, 10);
        last = p;
      }
    }
    system.tick();
    setVisible(false);
    for (int i = 0; i < system.numberOfParticles(); ++i) {
      Particle p = system.getParticle(i);
      if (p.age() > 40) {
        system.removeParticle(p);
        continue;
      }
      setVisible(true);
      fill(200, 128/( (p.age()*2)+1));
      ellipse(p.position().x(), p.position().y(), smokeSize, smokeSize);
    }
  }
}