BlackToWhite Rects

size(320,240);
background(0);

for(int i=0;i<250;i=i+1){
  int x = int(random(0,290));
  int y=int(random(0,200));
  int hw=int(random(10,40));
  fill(int(random(0,255)));
  stroke(255);rect(x,y,hw,hw);
}