Pen Settings

HTML

About HTML Preprocessors

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

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. So you don't have access to higher-up elements like the <html> tag. If you want to add classes there that can affect the whole document, this is the place to do it.

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).

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.

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About External Resources

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

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

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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.

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.

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About External Resources

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 esm.sh, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ESM usage.

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

If you're using React / ReactDOM, make sure to turn on Babel for the JSX processing.

Behavior

Auto Save

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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

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Visit your global Editor Settings.

HTML 

              
                <div class="entry frankenstein"></div>
!

CSS 

              
                black(alpha)
  rgba(0,0,0,alpha)
  
body
  background-color: #444
  position: relative
  height: 100vh
  
.entry
  position: absolute
  left: 50%
  top: 50%

  &:before,
  &:after
    display: block
    content: ''
    position: absolute
    
  &.frankenstein
    width: 130px
    height: 160px
    margin-left: -(@width/2)
    margin-top: -(@height/2)

    background-image: linear-gradient(to top, black(.1), black(.1)),
                      linear-gradient(to right, seagreen, seagreen),
                      linear-gradient(to bottom, darken(silver,10) 50%, silver 50%),
                      radial-gradient(circle, darken(seagreen,10) 25%,
                                              seagreen 25%,
                                              seagreen 50%,
                                              transparent 50%),
                      radial-gradient(circle, darken(seagreen,10) 25%,
                                              seagreen 25%,
                                              seagreen 50%,
                                              transparent 50%)
    background-repeat: no-repeat
    background-size: 50px 15px,
                     50px 100%,
                     70px 10px,
                     30px 30px,
                     30px 30px
    background-position: center 92%,
                         center 0,
                         center 95%,
                         -2px 60%,
                         103% 60%

    &:before
      width: 100px
      height: 135px
      left: 15px
      background-color: seagreen
      background-image: linear-gradient(to bottom, #222, #222),
                        radial-gradient(ellipse, #222 50%, transparent 50%),
                        radial-gradient(ellipse, #222 50%, transparent 50%),
                        radial-gradient(ellipse, #222 50%, transparent 50%),
                        radial-gradient(ellipse, #222 50%, transparent 50%),
                        radial-gradient(ellipse, #222 50%, transparent 50%),
                        radial-gradient(circle, #222 15%,
                                                tomato 15%,
                                                tomato 30%,
                                                white 30%,
                                                white 50%,
                                                transparent 50%),
                        radial-gradient(circle, #222 15%,
                                                tomato 15%,
                                                tomato 30%,
                                                white 30%,
                                                white 50%,
                                                transparent 50%),
                        linear-gradient(seagreen, seagreen),
                        radial-gradient(circle, seagreen 40%,
                                                darken(seagreen,10) 40%,
                                                darken(seagreen,10) 53%,
                                                transparent 42%),
                        linear-gradient(#333, #333)
      background-repeat: no-repeat
      background-size: 100% 15px,
                       15px 40px,
                       15px 40px,
                       15px 40px,
                       15px 40px,
                       15px 40px,
                       24px 24px,
                       24px 24px,
                       25px 13px,
                       25px 25px,
                       40px 2px
      background-position: 0 0,
                           -5px -10px,
                           6px -14px,
                           17px -12px,
                           93% -14px,
                           106% -10px,
                           18px 70px,
                           56px 70px,
                           center 70%,
                           center 75%,
                           center 85%
      border-radius: 6px 6px 15px 15px

    &:after
      width: 35px
      height: 12px
      left: 28px
      top: 68px
      background-color: #222
      border-radius: 4px
      box-shadow: 38px 0 0 #222,
                  -2px -8px 0 4px darken(seagreen,4),
                  30px -8px 0 4px darken(seagreen,4),
                  41px -8px 0 4px darken(seagreen,4)
!

JS
!
999px

Console