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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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Adding Classes

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About the <head>

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. If you need things in the <head> of the document, put that code here.

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Insecure Resource

The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.

CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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You can apply a script from anywhere on the web to your Pen. Just put a URL to it here and we'll add it, in the order you have them, before the JavaScript in the Pen itself.

If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.

You can also link to another Pen here, and we'll pull the JavaScript from that Pen and include it. If it's using a matching preprocessor, we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.

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Packages

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.

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About Packages

Using packages here is powered by Skypack, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ES6 import usage.

All packages are different, so refer to their docs for how they work.

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HTML 

              
                <ol reversed class="paces" lang="en">
	<li class="pace js">JS+<blockquote class="quote js">JS+: The JavaScript ecosystem (not the language!): Anyone else feels overwhelmed by the rate of rapid changes here?</blockquote>
	</li>
	<li class="pace css">CSS<blockquote class="quote css">CSS: This is moving in a nice click lately, with lots of useful new stuff enabled in the browsers</blockquote></li>
	<li class="pace html">HTML<blockquote class="quote html">HTML: Started with 20 something "tags", now we have over 100 "elements", but I feel that I've been able to keep up with the pace of change here</blockquote></li>
	<li class="pace url">URLs<blockquote class="quote url">URLs: Sadly they are frequently changing; links die. We should work hard to keep URLs unchanged, but that's not how it is</blockquote></li>
	<li class="pace http">HTTP<blockquote class="quote http">HTTP: Gradually changed (http/2), but it kind of feels good that it doesn't constantly change underneath us</blockquote></li>
	<li class="pace tcpip">TCP/IP<blockquote class="quote tcpip">TCP/IP: Deliberately dumb, simple, all it does is move packets around</blockquote></li>	
</ol>
<footer><blockquote><p>Fast gets all the attention,<br>
	but Slow has all the power</p><cite>Stewart Brand "Pacelayers"</cite>
</blockquote><a href="https://vimeo.com/373128517">The Layers of the Web - Jeremy Keith</a></footer>
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CSS 

              
                body {
	font-family: sans-serif;
	font-size: calc(0.5em + 1vmin);
	color: #eee;
	background-color: #111;
	width: 90%;
	max-width: 35em;
	margin-left: auto;
	margin-right: auto;
	padding: 2em;
}
.paces {
	margin: 0;
	padding: 0;
	list-style-type: none;
	position: relative;
	padding-top: 100%;
}
.pace {
	font-size: 90%;
	position: absolute;
	left: 0;
	top: 0;
	right: 0;
	bottom: 0;
	padding: 0.5em;
	text-align: center;
	border: 1px solid #fff;
	border-radius: 60%;
	background-color: rgba(255, 255, 255, 0.1);
	transition: all ease-in-out 0.2s;
	.quote {
		opacity: 0;
		margin: 0;
		padding: 0;
	}
	&:hover,
	&:focus,
	&:active {
		cursor: grabbing;
		background-color: #111;
		color: #111;
		animation: none !important;
		.quote {
			color: #fff;
			hyphens: auto;
			z-index: 100;
			opacity: 1;
			position: absolute;
			top: 50%;
			left: 50%;
			transform: translate(-50%, -50%);
		}
	}
}
.pace {
	&.js {
		margin: 5%;
		animation: 2.5s infinite linear rotate;
		box-shadow: 0 0 5em #fff;
	}
	&.css {
		margin: 10%;
		animation: 5s infinite linear rotate;
	}
	&.html {
		margin: 15%;
		animation: 10s infinite linear rotate;
	}
	&.url {
		margin: 20%;
		animation: 15s infinite linear rotate;
	}
	&.http {
		margin: 25%;
		animation: 25s infinite linear rotate;
	}
	&.tcpip {
		margin: 30%;
		animation: 35s infinite linear rotate;
	}
}
.quote {
	&.js {
		padding: 10%;
	}
	&.css {
		padding: 5%;
	}
	&.html {
		padding: 4%;
	}
}
footer {
	text-align: center;
	background-color: #111;
	transform: translateY(-80%);
	padding-top: 2em;
	padding-bottom: 2.5em;
	padding-left: 2em;
	padding-right: 2em;
	margin-left: -2em;
	margin-right: -2em;
	box-shadow: 0 -1em 1em #111;
	a {
		color: #666;
		text-decoration: none;
		&:hover,
		&:focus,
		&:active {
			color: #fff;
		}
	}
}
.quotes .quote {
	opacity: 0;
	&:target {
		position: absolute;
		top: 0;
		opacity: 1;
	}
}

@keyframes rotate {
	from {
		transform: rotate(0deg);
	}

	to {
		transform: rotate(360deg);
	}
}
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JS
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999px

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