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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

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

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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 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

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

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HTML 

              
                <body>
  
  <div id="container"></div>
  <script id="template">
    <div class="flip-card" on-click="toggle('flipCard')">{{ flipCard ? 'Reset' : 'Animate' }}</div>
    <div class="contact-wrapper">
        <div class="envelope {{ flipCard ? 'active' : '' }}">
          <div class="back paper"></div>
          <div class="content">
            <div class="form-wrapper">
              <form>
                <div class="top-wrapper">
                  <div class="input">
                    <label>Name</label>
                    <input type="text" name="name"/>
                  </div>
                  <div class="input">
                    <label>Phone</label>
                    <input type="text" name="phone"/>
                  </div>
                  <div class="input">
                    <label>Email</label>
                    <input type="text" name="_replyto"/>
                  </div>
                </div>
                <div class="bottom-wrapper">
                  <div class="input">
                    <label>Subject</label>
                    <input type="text" name="_subject"/>
                  </div>
                  <div class="input">
                    <label>Message</label>
                    <textarea rows="5" name="message"></textarea>
                  </div>
                  <div class="submit">
                    <div class="submit-card" on-click="toggle('flipCard')">Send Mail</div>
                  </div>
                </div>
              </form>
            </div>
          </div>
          <div class="front paper"></div>
        </div>
      </div>
    
  </script>
  
</body>
!

CSS 

              
                body
  background linear-gradient(45deg, #BB1881, #F88B50)
  font-family sans-serif

.contact-wrapper
  position absolute
  top 50%
  transform translateY(-50%)
  width 100%
  
.flip-card
  border-radius 0.5em
  position fixed
  top 1em
  left 1em
  width 5em
  padding 0.5em
  border 0.1em solid #fff
  color #fff
  text-align center
  cursor pointer
  z-index 9
.envelope
  position relative
  display block
  width 30em
  height 35em
  margin 0 auto
  &.active
    .content
      padding 15em 2em 2em
    .paper.front,
    .paper.back
      animation-duration 1.5s
      animation-direction normal
      animation-timing-function ease-in-out
      animation-fill-mode forwards
    .paper.front
      animation-name envelope-front
    .paper.back
      animation-name envelope-back
      &:before
        animation-duration 0.5s
        animation-direction normal
        animation-timing-function ease-in-out
        animation-fill-mode forwards
        animation-delay 1.25s
        animation-name envelope-back-before
    .bottom-wrapper
      transform rotateX(180deg)
      &:after
        z-index 0
        opacity 1
  
  .content
    padding 2em
    box-sizing border-box
    position relative
    z-index 9
    transition all 0.5s ease-in-out
    transition-delay 1s
    
  .top-wrapper,
  .bottom-wrapper
    box-sizing border-box
    background #03A9F5
    color #fff
    
  .top-wrapper
    padding 2em 2em 0
    border-top-left-radius 0.5em
    border-top-right-radius 0.5em
  
  .bottom-wrapper
    padding 0 2em 2em
    border-bottom-left-radius 0.5em
    border-bottom-right-radius 0.5em
    transition all 0.5s ease-in-out
    transform-origin top
    transform-style preserve-3d
    position relative
    overflow hidden
    margin-top -1px
    &:after
      position absolute
      content ''
      display block
      opacity 0
      background #03A9F5
      top 0
      left 0
      width 100%
      height 100%
      z-index -1
    
  form
    label
      display block
      padding-bottom 0.5em
    input,
    textarea
      width 100%
      box-shadow 0
      background transparent
      color #fff
    input
      border-width 0 0 0.1em
      border-color #fff
      border-style solid
    textarea
      border 0.1em solid #fff
      border-radius 0.25em
    .submit-card
      background #fff
      color #222
      text-align center
      padding 0.5em
      box-sizing border-box
      background #fff
      width 100%
      border 0
      box-shadow none
      border-radius 0.25em
      cursor pointer
    .input
      padding-bottom 1em
      
  .paper
    position absolute
    display block
    top 0
    left 0
    border-bottom-left-radius 0.5em
    border-bottom-right-radius 0.5em
    overflow hidden
    &.back
      top 0
      &:before
        content ''
        display block
        width 0
        height 0
        margin-bottom -1px
        border-style solid
        border-width 0 15em 10em 15em
        border-color transparent transparent #d3d3d3 transparent
        transform-origin bottom
        transform-style preserve-3d
        z-index 0
      &:after
        content ''
        display block
        background-color #d3d3d3
        width 30em
        height 20em
    &.front
      top 10em
      box-shadow 0.1em 0.5em 0.5em rgba(0,0,0,0.25)
      z-index 0
      &:before
        content ''
        display block
        width 0
        height 0
        border-style solid
        border-width 10em 15em 0 15em
        border-color transparent #fff
      &:after
        content ''
        display block
        width 30em
        height 10em
        background #fff
        margin-top -1px
@keyframes envelope-front {
  0 {
    top: 10em;
    z-index: 0;
  }
  
  50% {
    top: 15em;
    z-index: 9;
  }
  
  100% {
    top: 10em;
    z-index: 9;
  }
}

@keyframes envelope-back {
  0 {
    top: 0;
  }
  
  50% {
    top: 5em;
  }
  
  100% {
    top: 0;
  }
} 

@keyframes envelope-back-before {
  0 {
    border-color transparent transparent #d3d3d3 transparent
    transform: rotateX(0deg);
    z-index: 0;
  }
  
  100% {
    border-color transparent transparent #fff transparent
    transform: rotateX(180deg);
    z-index: 99;
    position: relative;
  }
}
!

JS 

              
                var ractive = new Ractive({
  el: '#container',
  template: '#template',
  data: {}
});
!
999px

Console