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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.

!
Insecure Resource

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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

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Babel includes JSX processing.

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HTML 

              
                <header class="main-header">
  <h1>Your Logo Here</h1>
  <nav>
    <ul>
      <li>Your</li>
      <li>Nav</li>
      <li>Here</li>
    </ul>
  </nav>
</header>

<main class="content">
  <p>The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy My brothers. And you will know My name is the Lord when I lay My vengeance upon thee.</p>
  
  <p>You think water moves fast? You should see ice. It moves like it has a mind. Like it knows it killed the world once and got a taste for murder. After the avalanche, it took us a week to climb out. Now, I don't know exactly when we turned on each other, but I know that seven of us survived the slide... and only five made it out. Now we took an oath, that I'm breaking now. We said we'd say it was the snow that killed the other two, but it wasn't. Nature is lethal but it doesn't hold a candle to man.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>Now that we know who you are, I know who I am. I'm not a mistake! It all makes sense! In a comic, you know how you can tell who the arch-villain's going to be? He's the exact opposite of the hero. And most times they're friends, like you and me! I should've known way back when... You know why, David? Because of the kids. They called me Mr Glass.</p>
    
  <p>Your bones don't break, mine do. That's clear. Your cells react to bacteria and viruses differently than mine. You don't get sick, I do. That's also clear. But for some reason, you and I react the exact same way to water. We swallow it too fast, we choke. We get some in our lungs, we drown. However unreal it may seem, we are connected, you and I. We're on the same curve, just on opposite ends.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy My brothers. And you will know My name is the Lord when I lay My vengeance upon thee.</p>
  
  <p>You think water moves fast? You should see ice. It moves like it has a mind. Like it knows it killed the world once and got a taste for murder. After the avalanche, it took us a week to climb out. Now, I don't know exactly when we turned on each other, but I know that seven of us survived the slide... and only five made it out. Now we took an oath, that I'm breaking now. We said we'd say it was the snow that killed the other two, but it wasn't. Nature is lethal but it doesn't hold a candle to man.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>Now that we know who you are, I know who I am. I'm not a mistake! It all makes sense! In a comic, you know how you can tell who the arch-villain's going to be? He's the exact opposite of the hero. And most times they're friends, like you and me! I should've known way back when... You know why, David? Because of the kids. They called me Mr Glass.</p>
    
  <p>Your bones don't break, mine do. That's clear. Your cells react to bacteria and viruses differently than mine. You don't get sick, I do. That's also clear. But for some reason, you and I react the exact same way to water. We swallow it too fast, we choke. We get some in our lungs, we drown. However unreal it may seem, we are connected, you and I. We're on the same curve, just on opposite ends.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy My brothers. And you will know My name is the Lord when I lay My vengeance upon thee.</p>
  
  <p>You think water moves fast? You should see ice. It moves like it has a mind. Like it knows it killed the world once and got a taste for murder. After the avalanche, it took us a week to climb out. Now, I don't know exactly when we turned on each other, but I know that seven of us survived the slide... and only five made it out. Now we took an oath, that I'm breaking now. We said we'd say it was the snow that killed the other two, but it wasn't. Nature is lethal but it doesn't hold a candle to man.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>Now that we know who you are, I know who I am. I'm not a mistake! It all makes sense! In a comic, you know how you can tell who the arch-villain's going to be? He's the exact opposite of the hero. And most times they're friends, like you and me! I should've known way back when... You know why, David? Because of the kids. They called me Mr Glass.</p>
    
  <p>Your bones don't break, mine do. That's clear. Your cells react to bacteria and viruses differently than mine. You don't get sick, I do. That's also clear. But for some reason, you and I react the exact same way to water. We swallow it too fast, we choke. We get some in our lungs, we drown. However unreal it may seem, we are connected, you and I. We're on the same curve, just on opposite ends.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>

  <p>The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy My brothers. And you will know My name is the Lord when I lay My vengeance upon thee.</p>
  
  <p>You think water moves fast? You should see ice. It moves like it has a mind. Like it knows it killed the world once and got a taste for murder. After the avalanche, it took us a week to climb out. Now, I don't know exactly when we turned on each other, but I know that seven of us survived the slide... and only five made it out. Now we took an oath, that I'm breaking now. We said we'd say it was the snow that killed the other two, but it wasn't. Nature is lethal but it doesn't hold a candle to man.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>Now that we know who you are, I know who I am. I'm not a mistake! It all makes sense! In a comic, you know how you can tell who the arch-villain's going to be? He's the exact opposite of the hero. And most times they're friends, like you and me! I should've known way back when... You know why, David? Because of the kids. They called me Mr Glass.</p>
    
  <p>Your bones don't break, mine do. That's clear. Your cells react to bacteria and viruses differently than mine. You don't get sick, I do. That's also clear. But for some reason, you and I react the exact same way to water. We swallow it too fast, we choke. We get some in our lungs, we drown. However unreal it may seem, we are connected, you and I. We're on the same curve, just on opposite ends.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy My brothers. And you will know My name is the Lord when I lay My vengeance upon thee.</p>
  
  <p>You think water moves fast? You should see ice. It moves like it has a mind. Like it knows it killed the world once and got a taste for murder. After the avalanche, it took us a week to climb out. Now, I don't know exactly when we turned on each other, but I know that seven of us survived the slide... and only five made it out. Now we took an oath, that I'm breaking now. We said we'd say it was the snow that killed the other two, but it wasn't. Nature is lethal but it doesn't hold a candle to man.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>Now that we know who you are, I know who I am. I'm not a mistake! It all makes sense! In a comic, you know how you can tell who the arch-villain's going to be? He's the exact opposite of the hero. And most times they're friends, like you and me! I should've known way back when... You know why, David? Because of the kids. They called me Mr Glass.</p>
    
  <p>Your bones don't break, mine do. That's clear. Your cells react to bacteria and viruses differently than mine. You don't get sick, I do. That's also clear. But for some reason, you and I react the exact same way to water. We swallow it too fast, we choke. We get some in our lungs, we drown. However unreal it may seem, we are connected, you and I. We're on the same curve, just on opposite ends.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy My brothers. And you will know My name is the Lord when I lay My vengeance upon thee.</p>
  
  <p>You think water moves fast? You should see ice. It moves like it has a mind. Like it knows it killed the world once and got a taste for murder. After the avalanche, it took us a week to climb out. Now, I don't know exactly when we turned on each other, but I know that seven of us survived the slide... and only five made it out. Now we took an oath, that I'm breaking now. We said we'd say it was the snow that killed the other two, but it wasn't. Nature is lethal but it doesn't hold a candle to man.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>Now that we know who you are, I know who I am. I'm not a mistake! It all makes sense! In a comic, you know how you can tell who the arch-villain's going to be? He's the exact opposite of the hero. And most times they're friends, like you and me! I should've known way back when... You know why, David? Because of the kids. They called me Mr Glass.</p>
    
  <p>Your bones don't break, mine do. That's clear. Your cells react to bacteria and viruses differently than mine. You don't get sick, I do. That's also clear. But for some reason, you and I react the exact same way to water. We swallow it too fast, we choke. We get some in our lungs, we drown. However unreal it may seem, we are connected, you and I. We're on the same curve, just on opposite ends.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>

  <p>The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy My brothers. And you will know My name is the Lord when I lay My vengeance upon thee.</p>
  
  <p>You think water moves fast? You should see ice. It moves like it has a mind. Like it knows it killed the world once and got a taste for murder. After the avalanche, it took us a week to climb out. Now, I don't know exactly when we turned on each other, but I know that seven of us survived the slide... and only five made it out. Now we took an oath, that I'm breaking now. We said we'd say it was the snow that killed the other two, but it wasn't. Nature is lethal but it doesn't hold a candle to man.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>Now that we know who you are, I know who I am. I'm not a mistake! It all makes sense! In a comic, you know how you can tell who the arch-villain's going to be? He's the exact opposite of the hero. And most times they're friends, like you and me! I should've known way back when... You know why, David? Because of the kids. They called me Mr Glass.</p>
    
  <p>Your bones don't break, mine do. That's clear. Your cells react to bacteria and viruses differently than mine. You don't get sick, I do. That's also clear. But for some reason, you and I react the exact same way to water. We swallow it too fast, we choke. We get some in our lungs, we drown. However unreal it may seem, we are connected, you and I. We're on the same curve, just on opposite ends.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>

  <p>The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy My brothers. And you will know My name is the Lord when I lay My vengeance upon thee.</p>
  
  <p>You think water moves fast? You should see ice. It moves like it has a mind. Like it knows it killed the world once and got a taste for murder. After the avalanche, it took us a week to climb out. Now, I don't know exactly when we turned on each other, but I know that seven of us survived the slide... and only five made it out. Now we took an oath, that I'm breaking now. We said we'd say it was the snow that killed the other two, but it wasn't. Nature is lethal but it doesn't hold a candle to man.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>Now that we know who you are, I know who I am. I'm not a mistake! It all makes sense! In a comic, you know how you can tell who the arch-villain's going to be? He's the exact opposite of the hero. And most times they're friends, like you and me! I should've known way back when... You know why, David? Because of the kids. They called me Mr Glass.</p>
    
  <p>Your bones don't break, mine do. That's clear. Your cells react to bacteria and viruses differently than mine. You don't get sick, I do. That's also clear. But for some reason, you and I react the exact same way to water. We swallow it too fast, we choke. We get some in our lungs, we drown. However unreal it may seem, we are connected, you and I. We're on the same curve, just on opposite ends.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>

  <p>The path of the righteous man is beset on all sides by the iniquities of the selfish and the tyranny of evil men. Blessed is he who, in the name of charity and good will, shepherds the weak through the valley of darkness, for he is truly his brother's keeper and the finder of lost children. And I will strike down upon thee with great vengeance and furious anger those who would attempt to poison and destroy My brothers. And you will know My name is the Lord when I lay My vengeance upon thee.</p>
  
  <p>You think water moves fast? You should see ice. It moves like it has a mind. Like it knows it killed the world once and got a taste for murder. After the avalanche, it took us a week to climb out. Now, I don't know exactly when we turned on each other, but I know that seven of us survived the slide... and only five made it out. Now we took an oath, that I'm breaking now. We said we'd say it was the snow that killed the other two, but it wasn't. Nature is lethal but it doesn't hold a candle to man.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>
  
  <p>Now that we know who you are, I know who I am. I'm not a mistake! It all makes sense! In a comic, you know how you can tell who the arch-villain's going to be? He's the exact opposite of the hero. And most times they're friends, like you and me! I should've known way back when... You know why, David? Because of the kids. They called me Mr Glass.</p>
    
  <p>Your bones don't break, mine do. That's clear. Your cells react to bacteria and viruses differently than mine. You don't get sick, I do. That's also clear. But for some reason, you and I react the exact same way to water. We swallow it too fast, we choke. We get some in our lungs, we drown. However unreal it may seem, we are connected, you and I. We're on the same curve, just on opposite ends.</p>
  
  <p>Now that there is the Tec-9, a crappy spray gun from South Miami. This gun is advertised as the most popular gun in American crime. Do you believe that shit? It actually says that in the little book that comes with it: the most popular gun in American crime. Like they're actually proud of that shit.</p>

</main>
!

CSS 

              
                * { box-sizing: border-box; }

html { font-size: 62.5%; }

body { 
  margin: 0;
  font-size: 1.8rem;
  font-family: 'Avenir', Arial, sans-serif;
}

.main-header {
  position: fixed;
  left: 0;
  top: 0;
  width: 100%;
  height: 6rem;
  color: white;
  background: #444;
  line-height: 6rem;
  transform: translateY(0);
  transform: translate3d(0,0,0);
  transition: .25s transform;
  backface-visibility: hidden;
}

.heads-up {
  transform: translateY(-6rem);
  transform: translate3d(0,-6rem,0);
}

.main-header h1 {
  float: left;
  font-size: 1.4rem;
  margin: 0 0 0 2rem;
  text-transform: uppercase;
}

.main-header nav {
  float: right;
  font-size: 1.4rem;
}

.main-header nav ul { 
  margin: 0; 
  padding: 0; 
}

.main-header nav li {
  display: inline-block;
  padding: 0 2rem;
  border-left: .1rem solid #555;
}

main { 
  padding: 10rem 6rem;
  background: #EEE;
}
!

JS 

              
                /*
* HeadsUp 1.5.6
* @author Kyle Foster (@hkfoster)
* @license MIT
*/
;(function( window, document, undefined ) {

  'use strict';

  // Extend function
  function extend( a, b ) {
    for( var key in b ) {
      if( b.hasOwnProperty( key ) ) {
        a[ key ] = b[ key ];
      }
    }
    return a;
  }

  // Throttle function (https://bit.ly/1eJxOqL)
  function throttle( fn, threshhold, scope ) {
    threshhold || ( threshhold = 250 );
    var previous, deferTimer;
    return function () {
      var context = scope || this,
          current = Date.now(),
          args    = arguments;
      if ( previous && current < previous + threshhold ) {
        clearTimeout( deferTimer );
        deferTimer = setTimeout( function () {
        previous   = current;
        fn.apply( context, args );
        }, threshhold );
      } else {
        previous = current;
        fn.apply( context, args );
      }
    };
  }

  // Class management functions
  function classReg( className ) {
    return new RegExp( '(^|\\s+)' + className + '(\\s+|$)' );
  }

  function hasClass( el, cl ) {
    return classReg( cl ).test( el.className );
  }

  function addClass( el, cl ) {
    if ( !hasClass( el, cl ) ) {
      el.className = el.className + ' ' + cl;
    }
  }

  function removeClass( el, cl ) {
    el.className = el.className.replace( classReg( cl ), ' ' );
  }

  // Main function definition
  function headsUp( selector, options ) {
    this.selector = document.querySelector( selector );
    this.options  = extend( this.defaults, options );
    this.init();
  }

  // Overridable defaults
  headsUp.prototype = {
    defaults : {
      delay       : 300,
      sensitivity : 20
    },

    // Init function
    init : function( selector ) {

      var self         = this,
          options      = self.options,
          selector     = self.selector,
          oldScrollY   = 0, 
          winHeight;

      // Resize handler function
      function resizeHandler() {
        winHeight = window.innerHeight;
        return winHeight;
      }

      // Scroll handler function
      function scrollHandler() {

        // Scoped variables
        var newScrollY = window.pageYOffset,
            docHeight  = document.body.scrollHeight,
            pastDelay  = newScrollY > options.delay,
            goingDown  = newScrollY > oldScrollY,
            fastEnough = newScrollY < oldScrollY - options.sensitivity,
            rockBottom = newScrollY < 0 || newScrollY + winHeight >= docHeight;

        // Where the magic happens
        if ( pastDelay && goingDown ) {
          addClass( selector, 'heads-up' );
        } else if ( !goingDown && fastEnough && !rockBottom || !pastDelay ) {
          removeClass( selector, 'heads-up' );
        }

        // Keep on keeping on
        oldScrollY = newScrollY;
      }

      // Attach listeners
      if ( selector ) {
        
        // Trigger initial resize
        resizeHandler();

        // Resize function listener
        window.addEventListener( 'resize', throttle( resizeHandler ), false );

        // Scroll function listener
        window.addEventListener( 'scroll', throttle( scrollHandler, 100 ), false );
      }
    }
  };

  window.headsUp = headsUp;

})( window, document );

// Instantiate HeadsUp
new headsUp( '.main-header' );
!
999px

Console