let extraCanvas;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  extraCanvas = createGraphics(windowWidth, windowHeight);

  extraCanvas.clear();

  background(0);

}

​

function draw() {

  rainbow(extraCanvas);

  image(extraCanvas, 0, 0, windowWidth, windowHeight);

}

​

function rainbow(canvas) {

  let r = noise(offset * 0.2) * 255;

  let g = noise(offset * 0.3) * 255;

  let b = noise(offset * 0.1) * 255;

​

  canvas.stroke(r, g, b);

  canvas.strokeWeight(20);

​

  let w = noise(offset * 0.1) * width;

  let h = noise(offset * 0.1) * height * 1.5;

​

  offset += 0.01;

​

  canvas.arc(width / 2, (height / 10) * 8, w, h, PI, 0);

}

​