createCanvas(500,500);
background(255);
noStroke();
stroke(0);
strokeWeight(5);
for(let i=0; i<19; i++){ arc(250,250,400-i*20,400-i*20,i*10-90,i*10); }
arc(250,250,400-i*20,400-i*20,i*10-90,i*10);
}