Pen Settings



CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource


Babel is required to process package imports. If you need a different preprocessor remove all packages first.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource


Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.


<section id="links">
  <a target="_blank" href="">View over Https</a>
  <a target="_blank" href="">Read Blog Post</a>

<div id="screen">


                html {background:#efefef; font-family:"Lato", "Lucida Grande","Lucida Sans Unicode", Tahoma, Sans-Serif; letter-spacing:-0.2px;}
body {margin:0px; padding:0px;}
#links {
  display:flex; padding:5px;
  a {
    display:block; padding:5px 15px;
    border: 3px solid #343436; border-radius: 3px;
    text-align:center; text-decoration:none; color:#fff;
    &:hover {background-color:#4d4d50;}

    #screen {
      position: relative;
      width: 100vw; height: 100vh;
      background: black;
      display: flex;
      align-items: stretch;
    #screen section {
      background-color: white;
      background-image: linear-gradient(to bottom, black 50%, white 50%);
      background-size: 20vh 20vh;
    #screen section:nth-of-type(2n) {
      background-color: black;
      background-position: 0 10vh;


                // set up audio context
var audioContext = (window.AudioContext || window.webkitAudioContext);
// create audio class
if (audioContext) {
  // Web Audio API is available.
  var audioAPI = new audioContext();
} else {
  // Web Audio API is not available. Ask the user to use a supported browser.
  alert("Oh nos! It appears your browser does not support the Web Audio API, please upgrade or use a different browser");

// variables
var analyserNode,
    frequencyData = new Uint8Array(256);
const screen = document.querySelector('#screen'),
    allRepeatedEls = document.querySelectorAll('#screen section'),
    totalEls = allRepeatedEls.length;

// create an audio API analyser node and connect to source
function createAnalyserNode(audioSource) {
  analyserNode = audioAPI.createAnalyser();
  analyserNode.fftSize = 512;

// get's html elements, loops over them & attaches a frequency from analysed data - what you do is up to you!
function animateStuff() {

  for (let i=0; i<totalEls; i++) {

    var freqVol = frequencyData[i*16];

    if (freqVol <= 255 && freqVol > 150) {
      allRepeatedEls[i].style.flex = 2;
    } else if (freqVol <= 150 && freqVol > 90) {
      allRepeatedEls[i].style.flex = 1.5;
    } else if (freqVol <= 90 && freqVol > 40) {
      allRepeatedEls[i].style.flex = 0.5;
    } else { //50 or below
      allRepeatedEls[i].style.flex = 1;      


// getUserMedia success callback -> pipe audio stream into audio API
var gotStream = function(stream) {
    // Create an audio input from the stream.
    var audioSource = audioAPI.createMediaStreamSource(stream);

// pipe in analysing to getUserMedia
navigator.mediaDevices.getUserMedia({ audio: true, video: false })