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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

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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).

Add External Stylesheets/Pens

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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.

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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="grid" dir="ttb">
  <main>
    <h1>This is the title of my main content</h1>
    <p>
      Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras convallis sodales erat vel accumsan. Nam eget massa nec sem vulputate ullamcorper vel quis justo. Duis rhoncus tempor tempus. Nulla facilisi. Maecenas nulla ante, lacinia ac consectetur non, aliquet sollicitudin libero. Quisque congue odio sodales dui fermentum ac laoreet mauris eleifend. Nulla facilisi. Phasellus vel erat a ante pharetra pharetra.</p>
    <div class="banner">
      <h2>This is an awesome banner</h2>
      <p>Depending on the container, this will adjust its font-size and paddings to fit perfectly</p>
    </div>
  </main>
  <aside>
    <ul>
      <li>Lorem ipsum dolor sit amet</li>
      <li>lacinia ac consectetur non</li>
      <li>Phasellus vel erat a ante</li>
      <li> Nulla facilisi</li>
      <li>ac consectetur non</li>
    </ul>
    <div class="banner">
      <h2>This is an awesome banner</h2>
      <p>Depending on the container, this will adjust its font-size and paddings to fit perfectly</p>
    </div>
  </aside>
</div>
!

CSS 

              
                @import url("https://fonts.googleapis.com/css2?family=Open+Sans:wdth@75..100&family=Oswald:wght@600&display=swap");
@layer presentation, defaultgrid, demo;

@layer demo {
  /*   Set container type */
  .grid > * {
    container-type: inline-size;
  }

  /* Style banner with cq units */
  .banner {
    padding: 3cqi;
    background: #55673e;
    font-size: clamp(1rem, 2cqi + 0.5rem, 1.5rem);
    border-radius: 0.5rem;
  }

  .banner h2 {
    font-size: clamp(1.3rem, 3cqi + 0.5rem, 2.4rem);
    margin: 0 0 1cqi;
  }

  /* Set container name for aside */
  aside {
    container-name: aside;
  }

  /* change the bgcolor when in the sidebar */
  @container aside (min-inline-size: 100px) {
    .banner {
      background-color: #2f1127;
    }
  }
}

@layer defaultgrid {
  .grid {
    display: grid;
    inline-size: 100%;
    max-inline-size: 1400px;
    gap: 3vmin;
    background: #69385c;
    border-radius: 2rem;
    overflow: hidden;
    > * {
      padding: 1.5rem;
    }
    @media screen and (min-width: 768px) {
      grid-template-columns: 2fr 1fr;
    }
  }
  aside {
    background: #715b64;
  }

  .banner p {
    margin: 0;
  }
}

@layer presentation {
  *,
  *::before,
  *::after {
    box-sizing: border-box;
  }

  body {
    display: flex;
    flex-direction: column;
    margin: 0;
    padding: 1rem;
    font-family: "Open Sans", sans-serif;
    font-size: 1.1rem;
    line-height: 1.55;
    color: white;
    min-block-size: 100dvb;
    place-content: center;
    place-items: center;
    background: #d3bdb0;
    /*     writing-mode: tb-rl; 
  }

  h1 {
    font-size: clamp(2rem, 5cqi + 0.5rem, 3rem);
  }

  h1,
  h2 {
    font-family: "Oswald", sans-serif;
    font-weight: 600;
  }
}
!

JS
!
999px

Console