void setup() {

  smooth();

  size(400,400);

  rectMode(CENTER);

}

float i = 180; // PI

float amplitude = 200; // 400/2

void draw() {

  background(200);

  drawSquares(5, 3);

}

void drawSquares(float s, int speed) {

  float x = (width/2)+sin(radians(i))*amplitude;

  float y = (height/2)+cos(radians(i))*amplitude;

  fill(0);

  rect(x,y,s,s);

  i-=speed; //change radians at the rate of speed

  amplitude-=0.5; //decrease amplitude to spiral inwards

  if(i==-180) {

    i=180; // reset radians

  }

  

  if(amplitude==0) {

    amplitude=width/2; // reset amplitude

  }

}