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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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CSS

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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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HTML 

              
                <div class="header" id="top">
   <h1>Scroll Down</h1>
   <i class="fa fa-angle-down animated bounce"></i>
</div>

<div class="section animate">
   <div class="middle">
      <img src="https://images.unsplash.com/photo-1460400408855-36abd76648b9?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
   </div>
   <div class="left title">
      <div class="content">
         <h2>A glorious nature shot.</h2>
         <p>Wow. What a wonderful image. And look! there are even more images on the right side. Amazing. If you click below, I bet you'll get teleported to a magical land.</p>
         <a href="#" class="btn-primary">Learn more</a>
      </div>
   </div>
   <div class="right tiles">
      <img src="https://images.unsplash.com/photo-1460400408855-36abd76648b9?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1460400408855-36abd76648b9?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1460400408855-36abd76648b9?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1460400408855-36abd76648b9?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
   </div>
</div>

<div class="section">
   <div class="middle">
      <img src="https://images.unsplash.com/photo-1464655646192-3cb2ace7a67e?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
   </div>
   <div class="right title">
      <div class="content">
         <h2>Check out this guy.</h2>
         <p>What an interesting looking person! I wonder if they've ever climbed Mount Everest, or seen the Egyptian Pyramids. If not, I hope that one day they get to. You go random stock image person! Follow your dreams!</p>
      </div>
   </div>
   
   <div class="left tiles">
      <img src="https://images.unsplash.com/photo-1464655646192-3cb2ace7a67e?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1464655646192-3cb2ace7a67e?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1464655646192-3cb2ace7a67e?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1464655646192-3cb2ace7a67e?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
   </div>
   
</div>

<div class="section">
   <div class="middle">
      <img src="https://images.unsplash.com/photo-1465326117523-6450112b60b2?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
   </div>
   <div class="left title">
      <div class="content">
         <h2>That is one pretty building.</h2>
         <p>I once thought about becoming an architect. I wanted to create a house fit for a king. But then I failed maths. So I became a frontend developer instead.</p>
      </div>
   </div>
   
   <div class="right tiles">
      <img src="https://images.unsplash.com/photo-1465326117523-6450112b60b2?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1465326117523-6450112b60b2?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1465326117523-6450112b60b2?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1465326117523-6450112b60b2?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
   </div>
   
</div>

<div class="section">
   <div class="middle">
      <img src="https://images.unsplash.com/photo-1464822759023-fed622ff2c3b?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
   </div>
   <div class="right title">
      <div class="content">
         <h2>The future is now.</h2>
         <p>Check out that technology! Imagine if we went back in time and put one of those in the hands of a neanderthal. Do you think they'd be impressed, or just try to club us to death?</p>
      </div>
   </div>
   
   <div class="left tiles">
      <img src="https://images.unsplash.com/photo-1464822759023-fed622ff2c3b?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1464822759023-fed622ff2c3b?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1464822759023-fed622ff2c3b?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
      <img src="https://images.unsplash.com/photo-1464822759023-fed622ff2c3b?dpr=2&auto=format&crop=entropy&fit=crop&w=250&h=250&q=80" />
   </div>
   
</div>

<div class="footer">
   <a href="#top" class="scrollTo"><i class="fa fa-angle-up animated bounce"></i></a>
   <h1>Scroll Up</h1>
</div>
!

CSS 

              
                @mixin vertical-align {
    position: relative;
    top: 50%;
    -webkit-transform: translateY(-50%);
    -ms-transform: translateY(-50%);
    transform: translateY(-50%);
}

@mixin transition {
    -moz-transition:    0.3s ease-in-out all;
    -o-transition:      0.3s ease-in-out all;
    -webkit-transition: 0.3s ease-in-out all;
    transition:         0.3s ease-in-out all;
}

@mixin filter($filter) {
   -webkit-filter: $filter;
   -moz-filter: $filter;
   -o-filter: $filter;
}

@import url(https://fonts.googleapis.com/css?family=Roboto:300,900);

$sm: 480px;
$md: 768px;
$lg: 992px;

body {
   font-family: 'Roboto', sans-serif;
}

.header, .footer {
   //height: 350px;
   background: #2e2e2e;
   color: #fff;
   padding: 30px;
   text-align:center;
   
   a {
      color: #fff;
   }
   //box-sizing: border-box;
   
   @media (min-width: $md) {
      padding: 100px 30px;
   }
   
   h1 {
      font-size: 4em;
      font-weight: 300;
   }
   
   i.fa {
      font-size: 4em;
   }
   
   .bounce {
      -webkit-animation-name: bounce;
      animation-name: bounce;
      -webkit-transform-origin: center bottom;
      transform-origin: center bottom;
      animation-iteration-count: infinite;
      -webkit-animation-iteration-count: infinite;
   }
   
   .animated {
     -webkit-animation-duration: 2s;
     animation-duration: 2s;
     -webkit-animation-fill-mode: both;
     animation-fill-mode: both;
   }
}

.section {
   width: 100%;
   position: relative;
   //height: 300px;
   
   .left, .middle, .right {
      width:100%;
      display: block;
      color: #fff;
      box-sizing: border-box;
      left: 0;
      padding: 30px;
      text-align:center;
      overflow:hidden;
      
      @include transition;
      
      .content {
         @media (min-width: $sm) {
            @include vertical-align();
         }
      }
      
      @media (min-width: $sm) {
         width: 50%;
         font-size:0.9em;
         padding: 10px;
         left: 0;
         float: left;
         position: absolute;
      }
      
      @media (min-width: $md) {
         width: 33.33333%;
         left: 33.33%;
         padding: 10px;
      }
      
      @media (min-width: $lg) {
         padding: 30px;
         font-size: 1em;
      }
   }
   
   &.animate {
      .left {
         left:0;
         
         @media (min-width: $sm) {
            left: 50%;
         }
         
         @media (min-width: $md) {
            left:0;
         }
      }
      
      .right {
         left:0;
         
         @media (min-width: $sm) {
            left: 50%;
         }
         
         @media (min-width: $md) {
            left:66.66%;
         }
      }
      
      
   }
   
   .title {
      background: tomato;
      
      h2 {
         margin-top:0;
      }
      
      p {
         line-height:1.55em;
         margin-bottom: 0.75em;
      }
      
      .btn-primary {
         color: #fff;
         background: darken(tomato, 10%);
         padding: 10px;
         text-decoration:none;
         border-radius: 3px;
         display:inline-block;
         @include transition;
         
         &:hover {
            background: darken(tomato, 15%);
         }
         
      }
   }
   
   .tiles {
      padding:0;
      background: #fff;
      clear:both;
      display:none;
      float:none;
      
      img {
         width:50%;
         float:left;
         height:auto;
         opacity: 0.7;
         @include transition;
         @include filter(grayscale(100%)); 
         
         
         &:hover {
            opacity:1;
            @include filter(grayscale(0%));
         }
      }
      
      @media (min-width: $md) {
           display:block;
      }
   }
   
   .middle {
      background: slategray;
      z-index: 2;
      padding:0;
      
      img {
         width: 100%;
         height: auto;
         display:block;
      }
   }
}

@-webkit-keyframes bounce {
    0%, 20%, 50%, 80%, 100% {-webkit-transform: translateY(0);}
    40% {-webkit-transform: translateY(-20px);}
    60% {-webkit-transform: translateY(-10px);}
} 
 
@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {transform: translateY(0);}
    40% {transform: translateY(-20px);}
    60% {transform: translateY(-10px);}
}
!

JS 

              
                $(document).ready(function(){

   var $sm = 480;
   var $md = 768;

   function resizeThis() {
      $imgH = $('.middle img').width();
      if ($(window).width() >= $sm) {
         $('.left,.right,.section').css('height', $imgH);
      } else {
         $('.left,.right,.section').css('height', 'auto');
      }
   }

   resizeThis();

   $(window).resize(function(){
      resizeThis();
   });

   $(window).scroll(function() {
      $('.section').each(function(){
         var $elementPos = $(this).offset().top;
         var $scrollPos = $(window).scrollTop();

         var $sectionH = $(this).height();
         var $h = $(window).height();
         var $sectionVert = (($h/2)-($sectionH/4));


         if (($elementPos - $sectionVert) <= $scrollPos && ($elementPos - $sectionVert) + $sectionH > $scrollPos) {
            $(this).addClass('animate');
         } else {
            $(this).removeClass('animate');
         }
      });
   });

   $('.btn-primary').click(function(){
      alert('I lied');
   });
});

$(function() {
  $('a[href*="#"]:not([href="#"])').click(function() {
    if (location.pathname.replace(/^\//,'') == this.pathname.replace(/^\//,'') && location.hostname == this.hostname) {
      var target = $(this.hash);
      target = target.length ? target : $('[name=' + this.hash.slice(1) +']');
      if (target.length) {
        $('html, body').animate({
          scrollTop: target.offset().top
        }, 1000);
        return false;
      }
    }
  });
});
!
999px

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