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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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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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Packages

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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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HTML 

              
                %p#reset
  %button Reset stack
#stack
  .card._1
    .front
      %p HTML
    .back
      %p HyperText Markup Language
  .card._2
    .front
      %p CSS
    .back
      %p Cascading Style Sheets
  .card._3
    .front
      %p PHP
    .back
      %p Hypertext Preprocessor
  .card._4
    .front
      %p SQL
    .back
      %p Structured Query Language
!

CSS 

              
                $cardW: 300px
$cardH: 180px
$bg: white
$line1: hotpink
$line2: lightblue
$flipTime: 1s

body
  background: #420
  font-family: Indie Flower, sans-serif

// button styles  
#reset
  text-align: center
  button
    background: rgba(0, 0, 0, 0.4)
    border: 0
    color: white
    font-size: 12pt
    margin: auto
    width: 120px
    height: 30px
    &:active
      background: rgba(0, 0, 0, 0.8)

// deck styles
#stack
  margin: auto
  position: relative
  width: $cardW

// card styles
.card
  border: 1px solid #888
  position: absolute
  width: $cardW
  height: $cardH
  transform-origin: 0% 0%
  .front
    background: $bg
    font-size: 24pt
    position: absolute
    width: $cardW
    height: $cardH
    z-index: 2
    p
      line-height: 3em
      text-align: center
  .back
    background: $bg linear-gradient(transparent, transparent 20%, $line1 20%, $line1 21%, transparent 21%, transparent 31%, $line2 31%, $line2 32%, transparent 32%, transparent 42%, $line2 42%, $line2 43%, transparent 43%, transparent 53%, $line2 53%, $line2 54%, transparent 54%, transparent 64%, $line2 64%, $line2 65%, transparent 65%, transparent 75%, $line2 75%, $line2 76%, transparent 76%, transparent 86%, $line2 86%, $line2 87%, transparent 87%, transparent 97%)
    font-size: 11pt
    position: absolute
    width: $cardW
    height: $cardH
    transform: rotateY(180deg)
    z-index: 1
    p
      margin: 40px 5px 5px 5px
      
// make hidden cards slightly visible
$maxCards: 4
@for $i from 1 through $maxCards
  ._#{$i}
    top: 0px + ($i * 3) - 3
    right: 0px + ($i * 2) - 2
    z-index: $maxCards - $i

// card states
.flipped
  transform: rotateY(180deg) translateX(30px)
  animation: flip $flipTime
  
.showingBack
  animation: showBack $flipTime
  
// animations for card states
@keyframes flip
  from
    transform: rotateY(0deg) translateX(0px)
  to
    transform: rotateY(180deg) translateX(30px)
  
@keyframes showBack
  0%
    z-index: 2
  25%
    z-index: 2
  50%
    z-index: 0
!

JS 

              
                $(function(){
  var maxCards = $('.card').length;
  // turn card
  for (var i = 1; i <= maxCards; ++i) {
    $('._' + i).click(function(){
      $(this).addClass('flipped');
      $(this).find('.front').addClass('showingBack');
      $(this).find('.front').css("z-index", 0);
      $(this).css("z-index", i);
    });
  }
  // reset stack
  $('#reset button').click(function(){
    $('.card').removeClass('flipped');
    $('.card').find('.front').removeClass('showingBack');
    $('.card').find('.front').css("z-index", 2);
    for (var j = 0; j < maxCards; ++j) {
      $('.card:eq(' + j + ')').css("z-index", maxCards - j);
    }
  });
});
!
999px

Console