const bg = 255;

​

const stepSize = 20;

const maxHeight = 50;

​

function setup() {

  createCanvas(400, 400);

  noLoop();

}

​

function draw() {

  background(bg);

  fill(bg);

  for(let y = 0; y < height; y += height/(lines + 1)) {

    drawLine(y);

  }

}

​

function drawLine(y) {

  beginShape();

  curveVertex(0, y);

  curveVertex(0, y);

  let x = 0;

  while(x < width) {

    curveVertex(x, y - maxHeight * random(0.2, 1) * volatility(x));

    x += stepSize;

  }

  curveVertex(width, y);

  curveVertex(width, y);

  endShape();

}

​

function volatility(x) {

  let t = (x/width) -0.25;

  return (0.5 * sin((t * TAU))) + 0.5;

}