Processing - rotating square

float angle;
float widthVar;
float rotationSpeed;

void setup()
{
  //set the size of the panel
  size(600,200);

  //initialization of parameters
  angle = 3;
  widthVar = 0;
  rotationSpeed = 0.1;

  fill(100);
  noStroke();
  rectMode(CENTER);
  rect(width/2,height/2, 40,40);
}

void draw()
{
  background(0);

  pushMatrix();
  //move the origin to the pivot point
  translate(width/2, height/2);
  //pivot the grid
  rotate(radians(angle));
  //
  rectMode(CENTER);
  fill(133*cos(widthVar)*cos(widthVar) + 130);
  rect(0, 0, 40*cos(widthVar),40);
  popMatrix();
  angle = angle + 2.5;
  widthVar = widthVar + rotationSpeed;
}