void setup (){
  size (600,600);
  background(255);
  smooth();
  noLoop();
  frameRate(60);
}

void draw (){

  int s = int(random(3,15));
  println(s);
  for (int x=0; x<width-5; x=x+s) {
    for (int y=0; y<height-5; y=y+s) {
      int a= int(random(2));     
      if (a==1){
        fill(255);
      }
      else {
        fill(random(255));
      }
      noStroke();
      ellipseMode(CORNER);
      ellipse(x, y, s, s);
    }
  }
  
  // save frame
  if(keyPressed) {
    if (key == 's' || key == 'S') {
      saveFrame("image-####.png");
    }
  }

}

void mousePressed() {
  background(255);
  redraw();
}