Trefoil

let c = [];
function setup() {
  s = min(windowWidth, windowHeight);
  createCanvas(s * 0.9, s * 0.9);
  c[0] = [];
  c[1] = [];
  trefoil();
}
function draw() {
  t = frameCount / 100;
  background(255 * cos(t / 3));
  translate(width / 2, height / 2);
  for (let i = 0; i < int(width / 10); i++) {
    stroke(10 + i * 9 * abs(sin(t / 10)));
    strokeWeight(0.1);
    plotT(i + (width / 4) * sin(t / 2));
  }
}
function trefoil() {
  for (let i = 0; i < TWO_PI * 70; i++) {
    c[0][i] = sin(i) + 2 * sin(2 * i);
    c[1][i] = cos(i) - 2 * cos(2 * i);
  }
}

function plotT(r) {
  noFill();
  beginShape();
  for (let i = 0; i < c[0].length; i++) {
    vertex(r * c[0][i], r * c[1][i]);
  }
  endShape(CLOSE);
}