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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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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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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.

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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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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 

              
                <article>
  <h1>Fancy Blockquote Style</h1>
  <p>Spaceflights cannot be stopped. This is not the work of any one man or even a group of men. It is a historical process which mankind is carrying out in accordance with the natural laws of human development.</p>

  <blockquote><p>I believe every human has a finite number of heartbeats. I don't intend to waste any of mine.</p></blockquote>

  <p>The regret on our side is, they used to say years ago, we are reading about you in science class. Now they say, we are reading about you in history class.</p>

  <p>Science has not yet mastered prophecy. We predict too much for the next year and yet far too little for the next 10.</p>
</article>
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CSS 

              
                @import url(https://fonts.googleapis.com/css?family=Droid+Serif:400,700);

body {
  padding: 25px;
  font-family: 'Droid Serif', serif;
  background: #4F7482;
  @media screen and (min-width: 750px) {
    padding: 50px;
  }
}

article {
  margin: 0 auto;
  background: #fff;
  max-width: 600px;
  border-radius: 3px;
  padding: 36px 50px;
  box-shadow: 0 2px rgba(0,0,0,.25);
  h1 {
    margin-top: 0;
    font-size: 2em;
    color: #4F7482;
    font-weight: 700;
    padding-bottom: .2em;
    border-bottom: 1px solid #c2c2c2;
  }
  p {
    font-size: 18px;
    line-height: 1.5em;
    margin-bottom: 28px;
  }
  blockquote {
    width: 100%;
    margin-left: -50px;
    padding: 36px 50px;
    position: relative;
    background: #c2c2c2;
    margin-bottom: 28px;
    &::before, &::after {
      top: 0;
      bottom: 0;
      width: 25px;
      content: '';
      position: absolute;
      background: #c2c2c2;
      box-shadow: 0 2px rgba(0,0,0,.25);
    }
    &::before {
      right: 100%;
    }
    &::after {
      left: 100%;
    }
    p {
      margin: 0;
      font-size: 1.5em;
      &::before {
        top: 0;
        left: 16px;
        color: #fff;
        content: '“';
        font-size: 3em;
        position: absolute;
        text-shadow: -3px 0 #c2c2c2;
      }
      &::after {
        right: 16px;
        color: #fff;
        content: '”';
        bottom: -32px;
        font-size: 3em;
        position: absolute;
        text-shadow: 3px 0 #c2c2c2;
      }
    }
  }
  
  @media screen and (min-width: 750px) {
    h1 {
      font-size: 3em;
    }
    blockquote {
      padding-right: 0;
      width: calc(100% + 50px);
      &::before {
        display: none;
      }
      &::after {
        width: 50px;
        border-radius: 0 3px 3px 0;
      }
      p {
        font-size: 2.5em;
        &::after {
          bottom: -56px
        }
      }
    }
  }
}
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JS
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