​

function setup() {

  createCanvas(windowWidth, windowHeight - 30);

  slider = createSlider(0, 10, 0.5, 0.01);

}

​

function sgn(a) {

  if (a > 0) {

    return 1;

  } else if (a < 0) {

    return -1;

  } else {

    return 0;

  }

}

​

function draw() {

  background(0);

  translate(width / 2, height / 2);

  stroke(255);

  noFill();

​

  let a = 100,

    b = a,

    n = slider.value();

​

  beginShape();

  for (let angle = 0; angle < TWO_PI; angle += 0.1) {

    let na = 2 / n;

    let x = pow(abs(cos(angle)), na) * a * sgn(cos(angle));

    let y = pow(abs(sin(angle)), na) * b * sgn(sin(angle));

​

    vertex(x, y);

  }

  endShape(CLOSE);

}