size(400, 400);
background(0);
stroke(255, 255, 255);
smooth();
fill(0);
strokeWeight(1);
int circleSize = 600;
int rectSize = 400;


while(circleSize > 2){
rect(200,200,rectSize,rectSize);
ellipse(200,200,circleSize,circleSize);
circleSize = circleSize - 20;
rectSize = rectSize - 20;

}