Problems working on Fisica. Please Help, Urgent!

I am working on a sketch with the contributed library, Fisica. I am trying to use the function of anchor and contact resize. But I don't know why my codes are not working with the contact resize part. Please....I really need your help, it frustrates me for a few days.

Here are my codes,

import fisica.*;

float frequency = -35;
float damping = -5;
float puenteY;


FBody[] steps = new FBox[15];
FWorld world;

int boxWidth = 500/(steps.length) -20;


void setup() {
  size(600, 600);
  smooth();

  puenteY = height/4;
  Fisica.init(this);

  world = new FWorld();
  world.setGravity(0, 100);
  world.setEdges();
  world.remove(world.left);
  world.remove(world.right);
  world.remove(world.top);
  world.setGrabbable(false);

  FCircle bola = new FCircle(40);
  bola.setPosition(width/2, puenteY-50);
  bola.setDensity(0.2);
  bola.setFill(random(50,200));
  bola.setNoStroke();
  world.add(bola);

  for (int i=0; i<steps.length; i++) {
    steps[i] = new FBox(boxWidth,10);
    steps[i].setPosition(map(i, 0, steps.length-1, boxWidth, width-steps.length), puenteY);
   // steps[i].setPosition(boxWidth*i+50, puenteY);
    steps[i].setNoStroke();
    steps[i].setFill(183, 218, 232);
    world.add(steps[i]);
  }

 for (int i=1; i<steps.length; i++) {
    FDistanceJoint junta = new FDistanceJoint(steps[i-1], steps[i]);
    junta.setAnchor1(boxWidth/2, 0);
    junta.setAnchor2(-boxWidth/2, 0);
    junta.setFrequency(frequency);
    junta.setDamping(damping);
    junta.setFill(118);
    junta.setNoStroke();
    junta.calculateLength();
    world.add(junta);
 }

  FCircle left = new FCircle(10);
  left.setStatic(true);
  left.setPosition(0, puenteY);
  left.setDrawable(false);
  world.add(left);

  FCircle right = new FCircle(10);
  right.setStatic(true);
  right.setPosition(width, puenteY);
  right.setDrawable(false);
  world.add(right);

  FDistanceJoint juntaPrincipio = new FDistanceJoint(steps[0], left);
  juntaPrincipio.setAnchor1(-boxWidth/2, 0);
  juntaPrincipio.setAnchor2(0, 0);
  juntaPrincipio.setFrequency(frequency);
  juntaPrincipio.setDamping(damping);
  juntaPrincipio.calculateLength();
  juntaPrincipio.setFill(118);
  juntaPrincipio.setNoStroke();
  world.add(juntaPrincipio);

  FDistanceJoint juntaFinal = new FDistanceJoint(steps[steps.length-1], right);
  juntaFinal.setAnchor1(boxWidth/2, 0);
  juntaFinal.setAnchor2(0, 0);
  juntaFinal.setFrequency(frequency);
  juntaFinal.setDamping(damping);
  juntaFinal.calculateLength();
  juntaFinal.setFill(118);
  juntaFinal.setNoStroke();
  world.add(juntaFinal);


}
void draw() {
  background(255);


    world.step();
  world.draw();
 if(keyPressed){
    if(key==' '){
      world.setGravity(0, -100);}
      else {
        world.setGravity(0, 100);}
  }


      if (frameCount % 100 == 0) {
    FCircle b = new FCircle(random(10, 40));
    b.setPosition(random(0,width), 50);
    b.setVelocity(0, 100);
    b.setRestitution(0);
    b.setNoStroke();
    b.setFill(random(50,200));
    world.add(b);
  }
}

void contactEnded(FContact c) {  
  if (!c.getBody1().isStatic()) {
    FCircle b = (FCircle)c.getBody1();
    if (b.getSize()>5) {
      b.setSize(b.getSize()*0.9);
    }
  } 

  if (!c.getBody2().isStatic()) {
    FCircle b = (FCircle)c.getBody2();
    if (b.getSize()>5) {
      b.setSize(b.getSize()*0.9);
    }
  }
}


void mousePressed() {
  float radius = random(10, 40);
  FCircle bola = new FCircle(radius);
  bola.setPosition(mouseX, mouseY);
  bola.setDensity(0.2);
  bola.setFill(random(50,200));
  bola.setNoStroke();
  world.add(bola);  
}



void keyReleased(){
    if(key==' '){
        world.setGravity(0, 100);}
      else {
        world.setGravity(0, -100);}

  }



void keyPressed() {
  if (key == 's' || key == 'S') saveFrame("_##.png");

}