float n = 100; // number of frames per animation cycle

void setup(){
  size(400, 400);
  frameRate(50); // number of frames per second
}

void draw(){
  background(255); // don't forget to clear at each frame

  float r1 = frameCount % n / n;
  rect(0, 0, width * r1, height * r1);

  float r2 = r1 - 0.5;
  ellipse(width * 0.5, height * 0.5, width * r2, height * r2);
  
  for(int i = 0; i < frameCount % n; i++){
    float y = height / n * i;
    line(0, y, y, y);
  }
}

void mouseMoved(){
}

void mouseDragged(){
}

void mousePressed(){
}

void mouseClicked(){
}