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HTML

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

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

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 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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Using packages here is powered by Skypack, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ES6 import usage.

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

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HTML 

              
                <div class="page">
  
  <!--Sidebar-->
  <div class="sidebar">
    <div class="panel">
     <div class="panel-header ">Project</div>

		  <!--Tree-->
      <div class="panel-body">
        
		    <ul class="tree-group">
          
          <li class="tree-item tree-item--chevron-down">
            <span class="tree-item-label tree-item-label--repo">vintage-shop</span>
            <ul class="tree-group">
              <li class="tree-item tree-item--chevron-right">
                <span class="tree-item-label tree-item-label--file-directory">git</span>
              </li>
              <li class="tree-item tree-item--chevron-right">
                <span class="tree-item-label tree-item-label--file-directory">dist</span>
              </li>
              <li class="tree-item tree-item--chevron-right">
                <span class="tree-item-label tree-item-label--file-directory">node_modules</span>
              </li>
              <li class="tree-item tree-item--chevron-right">
                <span class="tree-item-label tree-item-label--file-directory">src</span>
              </li>
              <li class="tree-item">
                <span class="tree-item-label tree-item-label--file-text">.editconfig</span>
              </li>
              <li class="tree-item">
                <span class="tree-item-label tree-item-label--file-text">build.js</span>
              </li>
              <li class="tree-item">
                <span class="tree-item-label tree-item-label--file-text">development.html</span>
              </li>
              <li class="tree-item">
                <span class="tree-item-label tree-item-label--file-text">LICENSE</span>
              </li>
              <li class="tree-item">
                <span class="tree-item-label tree-item-label--file-text">package-lock.json</span>
              </li>
              <li class="tree-item">
                <span class="tree-item-label tree-item-label--file-text">production.html</span>
              </li>
              <li class="tree-item">
                <span class="tree-item-label tree-item-label--file-book">README.md</span>
              </li>
              <li class="tree-item">
                <span class="tree-item-label tree-item-label--file-text">test.html</span>
              </li>
            </ul>
          </li>
         </ul>
       </div>

    </div>
  </div><!--Sidebar ends-->

  
  <div class="editor">
    
    <!--Editor 1 -->
    <div class="panel">
      
      <div class="panel-header">
        <div class="tabs">
          <div class="tab-item">scafolding.less</div>
          <div class="tab-item tab-item--selected">styles.less</div>
          <div class="tab-item">cart-item.stash</div>
        </div>
      </div>

      <div class="panel-body">
        <ol class="editor-container">
          <li class="editor-line"></li>
          <li class="editor-line"><span class="editor-content">Hey there!</span></li>
          <li class="editor-line"></li>
                  <p>
          Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse
          enim tortor, interdum eu consequat ac, ullamcorper ac lacus. Morbi
          sagittis diam a dui rhoncus, eget egestas augue tempor. Ut vitae
          ornare ex. Morbi malesuada, felis non molestie sollicitudin, arcu
          lorem blandit velit, non ultrices dolor quam quis metus. Nunc ut nisi
          eget dolor imperdiet gravida. Donec dapibus volutpat leo. Nullam
          suscipit efficitur nibh, pretium laoreet ante malesuada eu. Nam vitae
          bibendum ante. Ut vitae dolor eget nibh sagittis imperdiet at at
          lacus. Curabitur elementum luctus velit. Curabitur non molestie neque,
          at venenatis enim. Praesent imperdiet non risus nec sagittis.
          Phasellus interdum consequat volutpat. Vestibulum ante ipsum primis in
          faucibus orci luctus et ultrices posuere cubilia curae; Aenean cursus
          mauris est, at maximus turpis sollicitudin ut. Aliquam pretium velit
          enim, ut bibendum mi posuere a.
        </p>
        <p>
          Aliquam erat volutpat. Morbi justo mauris, viverra eu nibh in, rhoncus
          gravida quam. Fusce quis faucibus nisl, vel ultrices enim. Integer
          ornare at turpis nec feugiat. Aliquam erat volutpat. Curabitur
          fringilla varius velit ut vestibulum. Fusce finibus, metus nec congue
          pretium, massa erat efficitur nisl, quis faucibus erat mi sed tortor.
          Sed tincidunt neque sit amet aliquam pulvinar. Integer urna turpis,
          elementum ac tempor et, viverra eget justo. Mauris sed quam id enim
          euismod luctus.
        </p>
        <p>
          Nunc aliquam eros sem, id faucibus nisi tincidunt ut. Nam a lorem
          rhoncus, pulvinar arcu finibus, placerat arcu. Cras vestibulum cursus
          metus at fringilla. Suspendisse potenti. Nam magna mauris, ultricies
          at fringilla et, porta vel leo. Nam sit amet congue velit. Nullam
          vitae ligula ante. Proin sollicitudin tellus nec enim dictum, ac
          dictum orci malesuada. Praesent arcu nunc, volutpat vel tempor eu,
          pulvinar condimentum nisl.
        </p>
        <p>
          Vestibulum ante ipsum primis in faucibus orci luctus et ultrices
          posuere cubilia curae; Phasellus feugiat vehicula ligula, vitae dictum
          neque. Quisque purus ante, rutrum a rutrum non, ullamcorper ut lorem.
          Mauris auctor mauris a justo imperdiet, laoreet placerat mi hendrerit.
          Ut elementum, elit in feugiat facilisis, massa quam accumsan neque,
          aliquet maximus turpis justo eget quam. Nunc egestas sodales
          fringilla. Vestibulum placerat consectetur elementum.
        </p>
        <p>
          Phasellus tincidunt aliquet ipsum, ac semper mi viverra ultrices.
          Donec lacus turpis, maximus quis eleifend a, volutpat ut ante. Nulla
          sed libero nec purus luctus efficitur. Nullam hendrerit elit ut augue
          blandit ullamcorper. Vestibulum ante ipsum primis in faucibus orci
          luctus et ultrices posuere cubilia curae; Integer posuere ac elit et
          pretium. Vivamus eleifend risus quis diam pharetra, et ultrices turpis
          volutpat. Curabitur id aliquet nulla, eu commodo diam.
        </p>
        <p>
          Vestibulum facilisis massa vehicula, mollis urna sit amet, ullamcorper
          est. Mauris egestas dui vel consectetur vehicula. Aliquam erat
          volutpat. Sed velit ante, tincidunt vel lobortis a, bibendum at magna.
          Curabitur euismod non lorem sit amet porttitor. Praesent dignissim
          tellus nec laoreet tempus. Curabitur congue blandit nisl, in lobortis
          ligula ullamcorper eu. Donec tincidunt, nunc in condimentum dictum,
          leo velit egestas dui, sit amet tempor lectus odio quis massa. Morbi
          ac ex malesuada, gravida magna ac, vulputate arcu. Sed laoreet mattis
          urna vitae molestie. Vestibulum in velit sed augue rhoncus ultrices.
        </p>
        <p>
          Proin tempus libero at convallis vulputate. Mauris eu eros lacus. Cras
          libero ipsum, posuere non ante eget, dignissim rutrum velit. Curabitur
          ultrices magna eget orci volutpat, in porta dolor laoreet. Quisque
          ullamcorper consequat pellentesque. Aenean facilisis eget nisi sed
          lobortis. Suspendisse id tincidunt magna. Aenean facilisis nisi ex,
          non tempus nulla tristique et. Vestibulum ante ipsum primis in
          faucibus orci luctus et ultrices posuere cubilia curae; Pellentesque
          sed sapien massa. Integer felis ligula, malesuada et arcu ut, viverra
          pellentesque justo. Morbi congue, nisi a blandit ornare, enim felis
          sagittis justo, nec ultrices ex dolor porttitor magna. Integer ut nibh
          tempus, commodo orci imperdiet, sodales enim. Donec blandit nunc a
          aliquam congue. Aenean placerat rhoncus massa, ut auctor massa tempor
          vitae. Etiam ut lacus dignissim, bibendum purus in, egestas tellus.
        </p>
        <p>
          Ut in lectus et risus varius tristique eu et nulla. Curabitur velit
          nulla, pharetra nec porttitor ut, tempor at mi. Sed risus sapien,
          hendrerit sit amet tortor sed, ultrices vehicula leo. Pellentesque sed
          semper justo, et finibus justo. Morbi ultricies scelerisque magna,
          eget accumsan leo aliquam quis. Sed vestibulum bibendum augue, ut
          feugiat quam dictum vitae. Fusce hendrerit lectus sem, vel
          sollicitudin ex viverra maximus.
        </p>
         </ol>
       </div>
     </div>

     <!--Editor 2 -->
     <div class="panel window-2">
         
       <div class="panel-header">
         <div class="tabs">
           <div class="tab-item tab-item--selected">styles.less</div>
         </div>
       </div>

       <div class="panel-body">
         <ol class="editor-container">
           <li class="editor-line"></li>
           <li class="editor-line"><span class="editor-content">Hey there!</span></li>
           <li class="editor-line"></li>
         </ol>
       </div>
       
      </div>
    
  </div><!--Editor ends-->

	<!--Footer-->
	<div class="footer">
    <div class="footer-file-info">
      <span class="file-info-source">src/styles.less</span>
      <span class="file-info-location">2:5</span>
      </div>
    <div class="footer-controls">
      <a href="">LF</a>
      <a href="">UTF-8</a>
      <a href="">Less</a>
      <a href=""><span class="icon-git-branch"></span>master</a>
      <a href="">⬇︎ 5 ⬆︎</a>
      <a href=""><span class="icon-diff"></span>1 file</a>
      <a href=""><span class="icon-squirrel"></span></a>
    </div>
  </div>
  
</div><!--Grid structure ends-->

<!-- Control Bar for demo purposes-->
<div class="control-bar">
  <button id="window-1">Close Tabs to the Right</button>
	<button id="window-2">Split Right</button>
</div>
!

CSS 

              
                /** Read the guide at: http://bit.ly/2xIdHu0 **/

/** Variables & Mixins **/

@bar-height: 30px;

.ellipsis {
  overflow: hidden;
	text-overflow: ellipsis;
	white-space: nowrap;
}


/** Scafolding --------------------**/
body {
	margin: 0;
}

.page {
	display: grid;
	grid-template-rows: auto @bar-height;
	grid-template-columns: 300px 1fr;
	height: 100vh;
}


/** Panel Module **/
.panel {
	display: grid;
	grid-template-rows: @bar-height auto;
	height: calc(~"100vh -" @bar-height);
}

.panel-body {
	overflow: auto; 
}


/** Tabs Module **/
.tabs {
	display: grid;
	grid-template-columns: repeat(3, 1fr);
	height: 100%;
}

.tab-item {
	.ellipsis;
	text-align: center;
  padding: 6px;
}


/** Editor **/
.editor {
  display: grid;
  .window-2  {
    display: none;
  }
  &.editor--2-windows-layout {
		grid-template-columns: 1fr 1fr;
      .window-2 { 
       display: grid;
	  }
	}
}


/** Footer **/
.footer {
  display: grid;
  grid-template-columns: 1fr auto;
	grid-column-start: 1;
	grid-column-end:   3;
}

.footer-file-info {
  .ellipsis;
}

.footer-controls {
  display: flex;
  height: 100%;
  justify-content: flex-end;
  a {
    height: 100%;
    display: flex;
    align-items: center;
  }
}


/** Theme --------------------- **/


/** Icons 
  * From https://octicons.github.com/
**/
@font-face {
  font-family: 'octicons';
  src: url("data:application/x-font-ttf;charset=utf-8;base64,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") format('truetype');
  font-weight: normal;
  font-style: normal;
}

[class^="icon-"], [class*=" icon-"] {
  font-family: 'octicons' !important;
  speak: none;
  font-style: normal;
  font-weight: normal;
  font-variant: normal;
  text-transform: none;
  line-height: 1;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}
.icon-squirrel:before {
  content: "\e900";
}
.icon-repo:before {
  content: "\e901";
}
.icon-git-branch:before {
  content: "\e902";
}
.icon-diff:before {
  content: "\e905";
}


/** Variables **/
@gray-dark: #2c313a;
@gray-base: #5c6370;
@gray-light: #c5cad3;
@gray-lighter: #d7dae0;
@gray-lightest: #dcdfe4;
@blue: #1f96ff;
@border-default: 1px solid @gray-light;

/** Styles **/
body {
	background-color: @gray-lighter;
	font-family: -apple-system, system-ui, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
	font-size: 0.8rem;
	color: @gray-dark;
}


.sidebar {
	border-right: @border-default;
	.tree-group {
		padding: 0;
		margin: 0;
	}
	.tree-item {
		padding: 5px 0 5px 25px;
		list-style: none;
    position: relative;
    &:before {
     font-family: 'octicons' !important; 
     position: absolute;
     left: 10px;
    }
    &.tree-item--chevron-down:before {
      content: "\e907";
    }
    &.tree-item--chevron-right:before {
      content: "\e908";
    }
	}
  .tree-item-label {
    display: flex;
    &:before {
     font-family: 'octicons' !important; 
     font-size: 17px;
     margin-right: 10px;
    }
    &.tree-item-label--repo:before {
      content: "\e901";
    }
    &.tree-item-label--file-directory:before {
      content: "\e903";
    }
    &.tree-item-label--file-text:before {
      content: "\e904";
    }
    &.tree-item-label--file-book:before {
      content: "\e906";
    }
  }
	.panel-header {
		display: flex;
	  align-items: center;
	  justify-content: center;
	}
}

.editor {
	.tab-item {
		border-right: @border-default;
		border-bottom: @border-default;
    color: @gray-base;
		&.tab-item--selected {
			background-color: @gray-dark;
			color: @gray-lightest;
			border-color: @gray-dark;
		}
	}
	.panel-body {
		background-color: @gray-dark;
		color: @gray-lightest;
		font-family: "Courier New";
		font-size: 1rem;
		.editor-container {
			padding-left: 45px;
			margin-top: 0;
		}
		.editor-line {
			color: @gray-base;
		}
		.editor-content {
			color: @gray-light;
		}
	}
  .window-2  {
    border-left: 1px solid @gray-light;
  }
}

.footer {
  align-items: center;
	border-top: @border-default;
}
.footer-file-info {
  .file-info-source {
    padding: 0 10px;
  }
}
.footer-controls {
  a {
    padding: 0 10px;
    color: initial;
    text-decoration: none;
    [class*="icon-"] {
      font-size: 15px;
      margin-right: 5px;
    }
    &:hover {
      background-color: @gray-light;
    }
    .icon-squirrel {
      color: @blue;
    }
  }
}

/** Control Bar for demo purposes **/
.control-bar {
	position: fixed;
	bottom: 50px;
	right: 20px;
}
#window-1 {
  display: none;
}
!

JS 

              
                $( "#window-2" ).click(function (){
	$( ".editor" ).addClass( "editor--2-windows-layout" );
  $( "#window-1" ).show();
  $( "#window-2" ).hide();
});

$( "#window-1" ).click(function (){
	$( ".editor" ).removeClass( "editor--2-windows-layout" );
  $( "#window-2" ).show();
  $( "#window-1" ).hide();
});
!
999px

Console