PSystem ps;
Particle a, b, c;

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

  a = new Particle(width/2 - 50, 0, 0);
  a.fix();
  ps.addParticle(a);

  b = new Particle(width/2 + 50, 0, 0);
  ps.addParticle(b);
  
  c = new Particle(width/2, 70, 0);
  ps.addParticle(c);
  
  ps.defaultSpringDamping = 0.0001;
  
  ps.addSpring(a, b);
  Spring s = ps.addSpring(b, c);
  s.restLength = 100;
  ps.addSpring(c, a);
  
  ps.setGravity(0.06);
}

void loop() {

  a.setPos(mouseX, mouseY, 0);
  background(255);

  
  fill(10, 200, 30, 200);
  noStroke();
  beginShape(TRIANGLES);
  vertex(a.pos[0], a.pos[1], a.pos[2]);
  vertex(b.pos[0], b.pos[1], b.pos[2]);
  vertex(c.pos[0], c.pos[1], c.pos[2]);
  endShape();
  
  stroke(200, 100, 100, 150);
  fill(255, 0, 0);  
  ps.draw();
}