ArrayList particles;

void setup(){
  size(200,200);  smooth();
  
  particles = new ArrayList();		  // Initialize the arraylist  
  for (int i = 0; i < 15; i++)   particles.add(new Particle(random(width), random(height)));  
  println(particles.size()+" new particles");
}



void draw() {
  background(0);
  run();
  addParticle(mouseX,mouseY);
  
  fill(200);
  rect(0,0,5,particles.size());
}


//this is where I suspect the problem is
void run() {
  // Cycle through the ArrayList backwards b/c we are deleting 
  // I got this from the official example
  for (int i = particles.size()-1; i >= 0; i--) {
    Particle p = (Particle) particles.get(i);
    p.run();
    if (p.dead()) {
	particles.remove(i);
    }
  }
}


void addParticle(float _x, float _y) {
  particles.add(new Particle(_x, _y));
}

boolean dead() {
  if (particles.isEmpty())   return true;
  else   return false;
  }

 

class Particle {
  float r;
  float timer;
  float x,y;

  Particle(float _x, float _y) {
    x = _x;
    y = _y;
    r = 10.0;
    timer = random(50,130);
  }

  void run() {
    update();
    render();
  }

  // update location
  void update() {
    x+=random(-1,1);
    y+=random(-1,1);
    timer -= 1;
  }

  void render() {
    ellipseMode(CENTER);
    noStroke();
    fill(255,timer);
    ellipse(x,y,r,r);
  }
  
  boolean dead() {
    if (timer <= 0)   return true;
    else  return false;
    }
    
    
}