Pen Settings



CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URLs added here will be added as <link>s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.

+ add another resource


Babel includes JSX processing.

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


Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.


Auto Save

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.


  <div id="pulse_text" class="text">click to play</div>
  <div id="pulse" class="box">pulse</div>
  <div id="bounce_text" class="text">click to play</div>
  <div id="bounce" class="box">bounce</div>


                @import url('');

html {
  box-sizing: border-box;
  font-family: -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Oxygen-Sans,Ubuntu,Cantarell,"Helvetica Neue",sans-serif;
*, *:before, *:after {
  box-sizing: inherit;
body {
  margin: 0;
  padding: 0;

main {
  align-items: center;
  background-color: #1d1e22;
  display: flex;
  flex-direction: column;
  height: 100vh;
  width: 100vw;

.text {
  color: #E0E0E0;
  font-size: 16px;
  margin: 30px 0 10px;
  padding: 5px 40px;

#pulse {
  animation-iteration-count: 3;

.box {
  align-items: center;
  background-color: #fff;
  border: 4px solid rebeccapurple;
  color: rebeccapurple;
  cursor: pointer;
  display: flex;
  font-family: 'Luckiest Guy';
  font-size: 40px;
  height: 60px;
  justify-content: center;
  width: 400px;
  will-change: transform;


                // our elements
var pulseText = document.querySelector('#pulse_text');
var pulse = document.querySelector('#pulse');
var bounceText = document.querySelector('#bounce_text');
var bounce = document.querySelector('#bounce');

// function for playing our pulse animation
function playPulse () {
	// prevent extra clicks during animation
  pulse.removeEventListener('click', playPulse);
  // add the library's classes
  pulse.classList.add('animated', 'pulse');
  // hide the play text since we can't click during animation = 0;
// event listener calls a function so we can prevent extra clicks
pulse.addEventListener('click', playPulse);
// function to reset after animation ends
pulse.addEventListener('animationend', function () {
	// restore event listener
	pulse.addEventListener('click', playPulse);
  // remove library's classes so they can be placed again
  pulse.classList.remove('animated', 'pulse');
  // restore the text since we can now click again = 1;

// function to play our infinite bounce animation
bounce.addEventListener('click', function () {
	// check to see if library classes have been applied
	if (!bounce.classList.contains('animated')) {
  	// animation is not playing, we will start it
    // change text to explain how to stop animation
  	bounceText.innerText = 'click to stop';
    // add the library's classes
  	bounce.classList.add('animated', 'bounce', 'infinite');
  } else {
  	// animation is playing, we will stop it
    // change text to explain how to start animation
  	bounceText.innerText = 'click to play';
    // remove the library's classes
  	bounce.classList.remove('animated', 'bounce', 'infinite');