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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>

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Insecure Resource

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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).

Add External Stylesheets/Pens

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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.

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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 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.

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HTML 

              
                - word = 'Thanks'
%a.h-button.centered{'data-text'=>"Hover me","href"=>"#","aria-label"=>"#{word}"}
  - word.split(//).each do |letter|
    %span #{letter}
!

CSS 

              
                @import url('https://fonts.googleapis.com/css?family=Roboto:900')
$letters: 6

body
  background: #111
  
a
  font-family: 'Roboto', sans-serif
  font-weight: 900
  color: black
  text-decoration: none
  
.centered
  position: absolute
  left: 50%
  top: 50%
  transform: translate(-50%, -50%)
  
.h-button
  background: white
  padding: 20px
  width: 250px
  text-align: center
  
  span
    display: inline-block
    min-width: 0.30em
    text-transform: uppercase
    transition: .25s cubic-bezier(0.5,-1, 0.5, 2)
    opacity: 0
    transform: translate(0,-20px)
    
  &:before
    content: attr(data-text)
    position: absolute
    width: 100%
    left: 0
    transition: .25s cubic-bezier(0.5,-1, 0.5, 2)
    text-transform: uppercase
    letter-spacing: 3.5px
    opacity: 1
    transform: translate(0,0px)
    
  &:hover,&:focus
    &:before
      opacity: 0
      transform: translate(0, 20px) 
  
    span
      opacity: 1
      transform: translate(0, 0)
   
    @for $i from 1 through $letters
      span:nth-child(#{$i})
        transition-delay: 0.025s * $i
!

JS 

              
                // Nothing here ¯\_(ツ)_/¯
!
999px

Console