fullscreen boolean flip = false;
void setup()
{
size (500, 500);
background(255);
smooth();
}
void draw()
{
background(255);
noStroke();
fill(0);
for ( float i = 0; i <= height; i+=17)
{
ellipse(width/2, height/2, width-i, height-i);
translate(0,-7);
fill( 255 );
if(flip)
fill(0);
flip = !flip;
noLoop();
}
}