cssAudio - Activefile-genericCSS - ActiveGeneric - ActiveHTML - ActiveImage - ActiveJS - ActiveSVG - ActiveText - Activefile-genericVideo - ActiveLovehtmlicon-new-collectionicon-personicon-teamlog-outoctocatpop-outspinnerstartv

Pen Settings

CSS Base

Vendor Prefixing

Add External CSS

These stylesheets will be added in this order and before the code you write in the CSS editor. You can also add another Pen here, and it will pull the CSS from it. Try typing "font" or "ribbon" below.

Quick-add: + add another resource

Add External JavaScript

These scripts will run in this order and before the code in the JavaScript editor. You can also link to another Pen here, and it will run the JavaScript from it. Also try typing the name of any popular library.

Quick-add: + add another resource

Code Indentation


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.

              <h1>Synching Animation Clocks with the Web Animation API</h1>
<p>This demo was made for <a href="http://www.smashingmagazine.com/?p=210830">my post on Smashing Magazine about where web animation is headed.</a> It uses a <a href="https://github.com/web-animations/web-animations-js">polyfill</a> to enable the Web Animation API. (Psst: Check out the JavaScript and CSS to see how it's done.) To learn more about the Web Animation API, <a href="http://rachelnabors.com/waapi/">check out my WAAPI resource page!</a></p>
<div id="CSSCats">
  <h2>Cats animated with <br />CSS Animations</h2>
  <p>Currently, it is impossible to synch two separate animations with CSS animations. Try adding new cats animated with CSS below. Notice that they do not run in synch with each other.</p>
  <div class="cat withCSS"></div>
  <button onclick="animateNewCatWithCSS()">Add a Cat</button>

<div id="WAAPICats">
  <h2>Cats animated with the <br />Web Animation API</h2>
  <p>But with the Web Animation API, you're able to set the <code>startTime</code> value across animations to properly synch them. When you add cats with the Web Animation API, they run lockstep!</p>
  <div class="cat" id="withWAAPI"></div>
  <button onclick="animateNewCatWithWAAPI()">Add a Cat</button>
              /* All cats have the same dimensions and the same sprite for a background image. */
.cat {
  background: url(http://stash.rachelnabors.com/24ways2012/cat_sprite.png) -800px 0 no-repeat; 
  height: 200px; width: 400px;

/* The cats animated with CSS have their running animations set with CSS */
.cat.withCSS {
  animation: run-cycle;
  animation-duration: .75s;
  animation-timing-function: steps(13,end);
  animation-iteration-count: infinite;

/* The keyframes for the run cycle.
   This moves the background image sprite around. */
@keyframes run-cycle {  
  0% {background-position: -800px 0; }
  100% {background-position: -800px -2591px; } 

/* More information on this spriting technique in my 24 Ways article: 

/* It's all presentational from here on. 
   Nothing to see here! */
#CSSCats, #WAAPICats {
  display: inline-block;
  text-align: center;
  vertical-align: top;
  width: 400px;

@media only screen and (min-width: 850px) {

  #CSSCats, #WAAPICats {
    margin: 3em 1em;

#CSSCats p, #WAAPICats p {
  text-align: left;  

body { 
  background: #e5e6e9;
  color: #071933;
  font-family: 'Lato', sans-serif;
  font-size: 1em; 
  line-height: 1.5em;
  margin: 1em 1em;
  text-align: center;
  width: 100%;

@media only screen and (min-width: 850px) { 
  body {
    margin: 4em auto;
    width: 80%;
h1 {
  font-family: 'Aleo', sans-serif;
  font-weight: 200;
  font-size: 2em;
  line-height: 1.25em;

h2 {
  font-family: 'Aleo', sans-serif;
  font-weight: 400;
  font-size: 1.5em;
  line-height: 1.25em;  

p {
  margin: .5em 0;

button {
  background: #2d0d3c;
  border: 0;
  color: #f7e6ff;
  cursor: pointer;
  font-size: .9em;
  padding: .7em 2em;

@media only screen and (min-width: 850px) { 
  button {
    padding: 1em 3em;
    font-size: 1em;

code { font-family: monospace;}

a:link { color: #1954c0; } a:visited {color: #702096; }
a:hover, a:active, a:focus {
  color: #646d97;

              // Here we set up a keyframes object containing values set in an '@keyframes' CSS rule
var keyframes = [
  {backgroundPosition: "-800px 0"},
  {backgroundPosition: "-800px -2591px"}
// and a timing object, which contains values we'd normally put in the 'animation' CSS rule
var timing = {
  duration: 750,
  iterations: Infinity,
  easing: "steps(13, end)"

/* with the WAAPI's animate function, we apply both keyframes and timing objects to .cat#withWAAPI 
(Have a look in your DOM inspector!)*/
var catRunning = document.getElementById ("withWAAPI").animate(keyframes, timing);

/* A function that makes new cats! 
Goodie! This will be useful below. */
function addCat(){
  var newCat = document.createElement("div");
  return newCat;

/* This is the function that adds a cat to the CSS column */
function animateNewCatWithCSS() {
  // make a new cat
  var newCat = addCat();
  // Add the CSS class that kicks off the CSS animation

/* This is the function that adds a cat to the WAAPI column */
function animateNewCatWithWAAPI() {
  // make a new cat
  var newCat = addCat();
  // animate said cat with the WAAPI's "animate" function
  var newAnimationPlayer = newCat.animate(keyframes, timing);
  // set that player object's start time to be the same as the original .cat#withWAAPI
  newAnimationPlayer.startTime = catRunning.startTime;
Loading ..................