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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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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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Packages

Add Packages

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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About Packages

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

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

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HTML 

              
                 <div class="App gsReveal">
        <h1>Hello CodeSandbox</h1>
        <h2>Start editing to see some magic happen!</h2>
      </div>
      <div class="gsReveal">
        Nullam id dolor id nibh ultricies vehicula ut id elit. Donec sed odio
        dui. Cras justo odio, dapibus ac facilisis in, egestas eget quam. Nulla
        vitae elit libero, a pharetra augue. Maecenas faucibus mollis interdum.
        Donec ullamcorper nulla non metus auctor fringilla. Donec id elit non mi
        porta gravida at eget metus. Cras mattis consectetur purus sit amet
        fermentum. Cum sociis natoque penatibus et magnis dis parturient montes,
        nascetur ridiculus mus. Praesent commodo cursus magna, vel scelerisque
        nisl consectetur et. Donec id elit non mi porta gravida at eget metus.
        Cras mattis consectetur purus sit amet fermentum. Lorem ipsum dolor sit
        amet, consectetur adipiscing elit. Donec id elit non mi porta gravida at
        eget metus. Morbi leo risus, porta ac consectetur ac, vestibulum at
        eros. Maecenas faucibus mollis interdum. Vestibulum id ligula porta
        felis euismod semper. Vivamus sagittis lacus vel augue laoreet rutrum
        faucibus dolor auctor. Vivamus sagittis lacus vel augue laoreet rutrum
        faucibus dolor auctor. Maecenas faucibus mollis interdum. Donec
        ullamcorper nulla non metus auctor fringilla. Integer posuere erat a
        ante venenatis dapibus posuere velit aliquet.
      </div>
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CSS
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JS 

              
                const animateFrom = (elem, direction = 1) => {
      let x = 0,
        y = direction * 50;
      if (elem.classList.contains("gsRevealFromLeft")) {
        x = -50;
        y = 0;
      } else if (elem.classList.contains("gsRevalFromRight")) {
        x = 50;
        y = 0;
      }

      gsap.fromTo(
        elem,
        { x, y, autoAlpha: 0 },
        {
          duration: 3,
          x: 0,
          y: 0,
          autoAlpha: 1,
          ease: "expo",
          overwrite: "auto"
        }
      );
    };

    const hide = elem => gsap.set(elem, { autoAlpha: 0 });
    gsap.utils.toArray(".gsReveal").forEach(elem => {
      hide(elem);
      ScrollTrigger.create({
        trigger: elem,
        onEnter: () => animateFrom(elem),
        onEnterBack: () => animateFrom(elem, -1),
        onLeave: () => hide(elem)
      });
    });
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999px

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