// A simple Particle class, renders the particle as an image
  
  class Particle {
    PVector loc;
    PVector vel;
    PVector acc;
    float timer;
    PImage img;
  
    // One constructor
    Particle(PVector a, PVector v, PVector l, PImage img_) {
      acc = a.get();
      vel = v.get();
      loc = l.get();
      timer = 100.0;
      img = img_;
    }
  
    // Another constructor (the one we are using here)
    Particle(PVector l,PImage img_) {
      acc = new PVector(0.0,0.0,0.0);
      float x = (float) generator.nextGaussian()*0.3f;
      float y = (float) generator.nextGaussian()*0.3f - 1.0f;
      vel = new PVector(x,y,0);
      loc = l.get();
      timer = 100.0;
      img = img_;
    }
  
    void run() {
      update();
      render();
    }
    
    // Method to apply a force vector to the Particle object
    // Note we are ignoring "mass" here
    void add_force(PVector f) {
      acc.add(f);
    }  
  
    // Method to update location
    void update() {
      vel.add(acc);
      loc.add(vel);
      timer -= 2.5;
      acc.mult(0);
    }
  
    // Method to display
    void render() {
      imageMode(CORNER);
      tint(255,timer);
      image(img,loc.x-img.width/2,loc.y-img.height/2);
    }
  
    // Is the particle still useful?
    boolean dead() {
      if (timer <= 0.0) {
        return true;
      } else {
        return false;
      }
    }
  }