size(500,500);
background(0);
smooth();
stroke(255, 20, 255);
rectMode(CENTER);

int shapeSize = 400;
int kindOfShape = 0;

while(shapeSize > 10){

if(kindOfShape == 0){

fill(20, 20, 230);
ellipse(250,250,shapeSize,shapeSize);
kindOfShape = 1;
fill(20, 20, 250);
ellipse(500,500,shapeSize,shapeSize);
fill(20, 20, 250);
ellipse(0,500,shapeSize,shapeSize);
fill(20, 20, 250);
ellipse(500,0,shapeSize,shapeSize);
fill(20, 20, 250);
ellipse(0,0,shapeSize,shapeSize);

}else{

fill(20, 200, 20);
rect(250,250,shapeSize,shapeSize);
kindOfShape = 0;


}

shapeSize = shapeSize - 40;

}