int i;
size(300,300);
for(i=0;i<300;i+=10){
line(i,0,i,300);
}
 point(150,150);
 point(75,150);
 point(75,75);
 point(225,225);
 point(225,150);
 point(150,75);
 point(150,225);
 point(225,75);
 point(75,225);
 line(0,0,300,300);
 line(75,75,225,75);
 line(75,75,75,225);
 line(75,225,225,225);
 line(225,225,225,75);
 line(0,300,300,0);
 rect(150,150,20,20);
 rect(170,170,20,20);
 rect(190,150,20,20);
 rect(210,170,20,20);
 rect(230,150,20,20);
 rect(150,190,20,20);
 rect(150,230,20,20);
 rect(190,190,20,20);
 rect(230,190,20,20);
 rect(230,150,20,20);
 fill(255,0,0);
 stroke(0,255,0);
 rect(50,50,50,50);

 noFill();
 stroke(255,255,255);
 rect(85,85,40,40);
 fill(255,0,0);
 noStroke();
 rect(50,150,50,50);
 noStroke();
 fill(255,0,0);
 rect(50,200,50,50);