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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

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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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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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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.

If the stylesheet 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 CSS 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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About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient. For instance, CoffeeScript can help prevent easy-to-make mistakes and offer a cleaner syntax and Babel can bring ECMAScript 6 features to browsers that only support ECMAScript 5.

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You're using npm packages, so we've auto-selected Babel for you here, which we require to process imports and make it all work. If you need to use a different JavaScript preprocessor, remove the packages in the npm tab.

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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Use npm Packages

We can make npm packages available for you to use in your JavaScript. We use webpack to prepare them and make them available to import. We'll also process your JavaScript with Babel.

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HTML

            
              input#cbx.inp-cbx(type='checkbox' style='display: none;')
label.cbx(for='cbx')
  span
    svg(width='12px' height='9px' viewbox='0 0 12 9')
      polyline(points='1 5 4 8 11 1')
  span Reward yourself with a nap
!

CSS

            
              $primary: #3c53c7
$gray:  #B9B8C3

body
  min-height: 100vh
  display: flex
  justify-content: center
  align-items: center
  font-family: "Open Sans", sans-serif
  font-size: 16px
  color: #00104B
  
.cbx
  -webkit-user-select: none
  user-select: none
  -webkit-tap-highlight-color: transparent
  cursor: pointer
  span
    display: inline-block
    vertical-align: middle
    transform: translate3d(0,0,0)
    &:first-child
      position: relative
      width: 24px
      height: 24px
      border-radius: 50%
      transform: scale(1)
      vertical-align: middle
      border: 1px solid $gray
      transition: all .2s ease
      svg
        position: absolute
        z-index: 1
        top: 8px
        left: 6px
        fill: none
        stroke: white
        stroke-width: 2
        stroke-linecap: round
        stroke-linejoin: round
        stroke-dasharray: 16px
        stroke-dashoffset: 16px
        transition: all .3s ease
        transition-delay: .1s
        transform: translate3d(0,0,0)
      &:before
        content: ""
        width: 100%
        height: 100%
        background: #506EEC
        display: block
        transform: scale(0)
        opacity: 1
        border-radius: 50%
        transition-delay: .2s
    &:last-child
      margin-left: 8px
      &:after
        content: ""
        position: absolute
        top: 8px
        left: 0
        height: 1px
        width: 100%
        background: $gray
        transform-origin: 0 0
        transform: scaleX(0)
  &:hover span:first-child
    border-color: $primary
 
.inp-cbx:checked + .cbx
  span
    &:first-child
      border-color: $primary
      background: $primary
      animation: check .6s ease
      svg
        stroke-dashoffset: 0
      &:before
        transform: scale(2.2)
        opacity: 0
        transition: all .6s ease
    &:last-child
      color: $gray
      transition: all .3s ease
      &:after
        transform: scaleX(1)
        transition: all .3s ease
    
@keyframes check
  50%
    transform: scale(1.2)
!

JS
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