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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

The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.

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

Any URLs added here will be added as <link>s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.

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You can apply CSS to your Pen from any stylesheet on the web. Just put a URL to it here and we'll apply it, in the order you have them, before the CSS in the Pen itself.

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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.

Add External Scripts/Pens

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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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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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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 

              
                <!-- copied over from https://developer.mozilla.org/en-US/blog/getting-started-with-css-container-queries/ -->

<div class="wrapper-container">
  <div class="wrapper">
    <main class="grid-container">
      <h2>Latest stories</h2>
      <ul class="grid">
        <li class="article-container">
          <article>
            <img
              src="https://images.unsplash.com/photo-1550098612-4838745601bf?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NTQ1ODh8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Bluetit on a branch" />
            <div>
              <h3>
                Why all fossil fuels must decline rapidly to stay below 1.5C
              </h3>
              <p>
                Lorem ipsum dolor, sit amet consectetur adipisicing elit.
                Exercitationem, nihil explicabo adipisci iste saepe reiciendis.
              </p>
            </div>
          </article>
        </li>
        <li class="article-container">
          <article>
            <img
              src="https://images.unsplash.com/photo-1551802230-22c087b11df2?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NjE2MDN8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Tree at sunset" />
            <div>
              <h3>
                Africa's extreme weather has killed at least 15,000 people in
                2023
              </h3>
              <p>
                Lorem ipsum dolor, sit amet consectetur adipisicing elit. Aut
                illo, possimus voluptates.
              </p>
            </div>
          </article>
        </li>
        <li class="article-container" style="--featured: true">
          <article>
            <img
              src="https://images.unsplash.com/photo-1589787787683-59c1409124c7?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NjE2NTB8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Robin on a branch" />
            <div>
              <h3>
                Fixing the gaps in England's ‘biodiversity net-gain' policy
              </h3>
              <p>
                Lorem ipsum dolor sit, amet consectetur adipisicing elit. Vitae
                sapiente quisquam voluptate omnis.
              </p>
            </div>
          </article>
        </li>
        <li class="article-container">
          <article>
            <img
              src="https://images.unsplash.com/photo-1546367564-e9be23af3d14?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NjE5NzV8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Car driving in snow" />
            <div>
              <h3>Factcheck: 21 misleading myths about electric vehicles</h3>
              <p>
                Lorem ipsum dolor, sit amet consectetur adipisicing elit. Aut
                illo, possimus voluptates accusamus nihil culpa odit vitae.
              </p>
            </div>
          </article>
        </li>
        <li class="article-container">
          <article>
            <img
              src="https://images.unsplash.com/photo-1582032951374-314efb7ccb76?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NjE0Njd8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Arctic sea ice" />
            <div>
              <h3>Global temperatures throughout mid-2023 shatter records</h3>
              <p>
                Lorem ipsum dolor, sit amet consectetur adipisicing elit. Aut
                illo, possimus voluptates accusamus nihil culpa odit vitae.
              </p>
            </div>
          </article>
        </li>
        <li class="article-container">
          <article>
            <img
              src="https://images.unsplash.com/photo-1509391366360-2e959784a276?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NjE3MDR8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Solar panels" />
            <div>
              <h3>
                UK renewables still cheaper than gas, despite auction setback
                for offshore wind
              </h3>
              <p>
                Lorem ipsum dolor, sit amet consectetur adipisicing elit. Aut
                illo, possimus voluptates accusamus nihil culpa odit vitae.
              </p>
            </div>
          </article>
        </li>
        <li class="article-container">
          <article>
            <img
              src="https://images.unsplash.com/photo-1679820024011-d7c428c47a36?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NjE4MjZ8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Wind turbine from below" />
            <div>
              <h3>
                EU's use of fossil fuels for electricity falls 17% to ‘record
                low' in first half of 2023
              </h3>
              <p>
                Lorem ipsum dolor, sit amet consectetur adipisicing elit. Aut
                illo, possimus voluptates accusamus nihil culpa odit vitae.
              </p>
            </div>
          </article>
        </li>
      </ul>
    </main>

    <aside class="grid-container">
      <h2>Popular this week</h2>
      <ul class="grid">
        <li class="article-container">
          <article>
            <img
              src="https://images.unsplash.com/photo-1615053835734-7752878e939e?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NjE5MDh8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Power plant" />
            <div>
              <h3>
                Plans for new oil and gas power plants have grown by 13% in 2023
              </h3>
              <p>
                Lorem ipsum dolor, sit amet consectetur adipisicing elit. Aut
                illo, possimus voluptates accusamus nihil culpa odit vitae.
              </p>
            </div>
          </article>
        </li>
        <li class="article-container">
          <article>
            <img
              src="https://images.unsplash.com/photo-1635351235165-23b8cd066ea6?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NjIwMjN8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Flooded city street" />
            <div>
              <h3>
                How climate change affects extreme weather around the world
              </h3>
              <p>
                Lorem ipsum dolor, sit amet consectetur adipisicing elit. Aut
                illo, possimus voluptates accusamus nihil culpa odit vitae.
              </p>
            </div>
          </article>
        </li>
        <li class="article-container" style="--featured: true">
          <article>
            <img
              src="https://images.unsplash.com/photo-1413882353314-73389f63b6fd?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMjM4NDZ8MHwxfHJhbmRvbXx8fHx8fHx8fDE2OTg3NjE3NjR8&ixlib=rb-4.0.3&q=80&w=400"
              alt="Electricity pylons" />
            <div>
              <h3>
                How ‘Shared Socioeconomic Pathways' explore future climate
                change
              </h3>
              <p>Lorem ipsum dolor, sit amet consectetur adipisicing elit.</p>
            </div>
          </article>
        </li>
      </ul>
    </aside>
  </div>
</div>
!

CSS 

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

body {
  margin: 0;
  min-height: 100vh;
  background: whitesmoke;
  font-family: Montserrat, sans-serif;
  line-height: 1.3;
}

img {
  display: block;
  width: 100%;
  aspect-ratio: 3 / 2;
  object-fit: cover;
}

ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

h2 {
  padding-bottom: 0.2em;
  margin: 0 0 0.6em;
  border-bottom: 2px solid;
}

article * {
  margin: 0;
}

aside {
  background: #f5f8ff;
  padding: var(--gap);
}

.wrapper {
  max-width: 1650px;
  margin: 0 auto;
  padding: clamp(1rem, 10cqi, 3rem);
  background: white;
}

h3 {
  font-size: 1.3em;
  margin-bottom: 0.2em;
  line-height: 1.24;
  text-wrap: balance;
}

.wrapper-container {
  container: wrapper / inline-size;
}

.wrapper {
  --gap: clamp(1rem, 5cqi, 2rem);
  display: grid;
  gap: var(--gap);
}

@container wrapper (min-width: 1250px) {
  .wrapper {
    grid-template-columns: 4fr 1fr;
  }
}

.grid-container {
  container: layout / inline-size;
}

.grid {
  display: grid;
  gap: var(--gap);
  margin-top: var(--gap);
}

@container layout (inline-size > 800px) {
  .grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .article-container:first-child {
    grid-column: span 2;
  }
}

@container layout (inline-size > 1000px) {
  .grid {
    grid-template-columns: repeat(4, 1fr);
  }

  .article-container:first-child {
    grid-column: span 4;
  }

  .article-container:nth-child(2),
  .article-container:nth-child(3) {
    grid-column: span 2;
  }
}

.article-container {
  container: article / inline-size;
}

article {
  display: grid;
  gap: calc(var(--gap) * 0.6);
  font-size: clamp(0.9rem, 3cqi, 1.75rem);
}

@container style(--featured: true) {
  article {
    position: relative;
    overflow: hidden;
    border-radius: 0.2rem;
    background: #e1e7f5;
    padding: calc(var(--gap) * 0.8);
  }

  article::before {
    content: "";
    width: 2.75rem;
    aspect-ratio: 1;
    position: absolute;
    top: -0.35rem;
    left: -0.35rem;
    border-radius: 50%;
    background-color: #7e9bde;
    background-position: center;
    background-size: 70%;
    background-repeat: no-repeat;
    background-image: url("data:image/svg+xml,%3C%3Fxml version='1.0' %3F%3E%3Csvg baseProfile='tiny' height='24px' id='Layer_1' version='1.2' viewBox='0 0 24 24' width='24px' xml:space='preserve' xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink'%3E%3Cg%3E%3Cg%3E%3Cpath d='M9.362,9.158c0,0-3.16,0.35-5.268,0.584c-0.19,0.023-0.358,0.15-0.421,0.343s0,0.394,0.14,0.521 c1.566,1.429,3.919,3.569,3.919,3.569c-0.002,0-0.646,3.113-1.074,5.19c-0.036,0.188,0.032,0.387,0.196,0.506 c0.163,0.119,0.373,0.121,0.538,0.028c1.844-1.048,4.606-2.624,4.606-2.624s2.763,1.576,4.604,2.625 c0.168,0.092,0.378,0.09,0.541-0.029c0.164-0.119,0.232-0.318,0.195-0.505c-0.428-2.078-1.071-5.191-1.071-5.191 s2.353-2.14,3.919-3.566c0.14-0.131,0.202-0.332,0.14-0.524s-0.23-0.319-0.42-0.341c-2.108-0.236-5.269-0.586-5.269-0.586 s-1.31-2.898-2.183-4.83c-0.082-0.173-0.254-0.294-0.456-0.294s-0.375,0.122-0.453,0.294C10.671,6.26,9.362,9.158,9.362,9.158z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
  }
}

@container article (inline-size > 500px) {
  article {
    grid-template-columns: 1fr 2fr;
  }
}

@container article (inline-size > 800px) {
  article {
    grid-template-columns: 1fr 1fr;
    gap: var(--gap);
  }
}
!

JS
!
999px

Console