size(300, 220); 
background(0);
smooth();
noStroke();
fill(255);
rect(20, 20, 80, 80);
fill(255, 0, 0);
rect(40, 40, 80, 80);
fill(255, 0, 0);
rect(150, 20, 80, 80);
fill(255);
rect(170, 40, 80, 80);