Box [] boxes = new Box[500];

void setup() {
  background(0);
  size( $(window).width(),
        $(window).height() );
  noSmooth();
  noStroke();
  rectMode(CENTER);
  
  
  for(int i = 0; i < boxes.length; i++) {
    boxes[i]=new Box();
  }
  
}

void draw() {
  for(int i = 0; i < boxes.length; i++) {
    boxes[i].update();
    boxes[i].draw();
  }

}

class Box {
  int x, y;
  float rwidth, rheight;
  
  Box() {
  }
  
  void update() {
    rwidth = random(50);
    rheight = random(50);
    float dark = random(-.1, 1.1);
    fill(
    random(100, 120)*dark, 
    random(100, 120)*dark, 
    random(90, 110)*dark, 
    25
    );
//    fill(random(90), 25);
    x = int(random(-1,101))*width/100;
    y = int(random(-1,101))*height/100;
  }
  
  void draw() {
    rect(x, y, rwidth, rheight);
  }
  
}