【p5.js】spiral

function setup() {
  createCanvas(400, 400);
  background(255);
  noStroke();
  fill(0);

  let x, y;
  let r, theta;
  const a = 5;

  for (let j = 0; j < 5; j++) {
    for (let i = 0; i <= 360; i+=10) {
      theta = map(i+360*j, 0, 360, 0, PI*2);
      r = a * theta;
      x = r * cos(theta) + width/2;
      y = -r * sin(theta) + height/2;
      ellipse(x, y, 5, 5);
    }
  }

  save('spiral.png');
}