class RectParticle extends Particle {
public RectParticle() {}

  void draw() {
    push();
    translate(pos[0], pos[1], pos[2]);
    if (this == mPart) {
      fill(#00FF00);
    }
    else if (fixed()) {
      fill(#FF0000);
    }
    else {
      fill(200);
    }
    box(10, 10, 10);
    pop();
  }
}

PSystem ps;

Particle a;
Particle b;
Particle c;
Particle mPart;

void setup() {
  size(400,400);
  ps = (PSystem)loadPlugin("PSystem");

  a = new RectParticle();
  a.setPos(width/2 + 50, height/2 - 50, 0);
  a.fix();
  ps.addParticle(a);

  b = new RectParticle();
  b.setPos(width/2 + 30, height/2 - 30, 0);
  ps.addParticle(b);

  c = new RectParticle();
  c.setPos(width/2 + 20, height/2 - 20, 80);
  ps.addParticle(c);
  
  mPart = new RectParticle();
  mPart.setPos(width/2, height/2, 20);
  mPart.fix();
  ps.addParticle(mPart);
  ps.addMagnet(mPart, 2);

  ps.addSpring(a, b);
  ps.addSpring(b, c);
}


void mouseDragged() {
  a.setPos(mouseX, mouseY, 0);
}

void mousePressed() {
  a.setPos(mouseX, mouseY, 0);
}

void loop() {
  background(#99CCCC);
  ps.draw();
}