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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>

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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

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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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HTML 

              
                <body class="background">
  <main>
    <h1>Scrolling Gradient</h1>

    <p>
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Animi error
      fugit in inventore minus reiciendis repellendus temporibus vitae
      voluptas, voluptate! Asperiores cum enim esse fuga hic quos rem
      repudiandae vel?
    </p>

    <p>
      Aliquam aut autem, culpa deserunt eligendi, facere fugit harum illum
      ipsa ipsum laboriosam magnam odit quaerat quos repudiandae, tempore
      ullam? Facilis magni nam neque nobis perspiciatis quos sit tempore
      veritatis?
    </p>

    <p>
      Accusamus asperiores earum illo illum itaque, necessitatibus nemo nihil
      praesentium quia quod sed sunt vitae. Ab aperiam nemo quo sed suscipit.
      Aliquid animi deleniti ex quod reiciendis sed tempora voluptatibus!
    </p>

    <p>
      Asperiores autem dolorum error, excepturi ipsam, iure magni nihil nobis
      nostrum nulla obcaecati odio porro qui, sapiente suscipit tempore vitae?
      Accusamus adipisci aliquam delectus earum eius facere ipsam officia
      provident.
    </p>

    <p>
      At blanditiis, cum delectus et facere fugit libero. Amet eaque est
      maxime minima odio perferendis? A culpa deleniti dicta, dolorum illo
      inventore modi nihil nisi, pariatur porro quasi quibusdam, quidem?
    </p>

    <p>
      Ad aut cumque dolorem expedita iusto mollitia perferendis repellendus.
      Aperiam aut consequatur deserunt dignissimos fugiat harum ipsum
      laboriosam laudantium libero odio possimus praesentium quo repellendus
      sed, veritatis vero voluptates voluptatibus!
    </p>

    <p>
      Harum ipsam molestiae quibusdam repudiandae ullam! Cupiditate est
      excepturi illo nihil reiciendis voluptatum! Aperiam blanditiis deleniti
      fugiat illo in quidem sed? Accusantium beatae consequuntur delectus
      error esse excepturi maxime nulla?
    </p>

    <p>
      Beatae consequuntur culpa delectus dignissimos harum iure quasi rerum
      tempora! Commodi exercitationem fugiat illum nobis optio sapiente! Aut
      dolor, eius error et ipsam labore nesciunt, nisi odit omnis, quas quasi.
    </p>

    <p>
      At blanditiis consequatur cumque, dolorum et facilis illum magni minima
      molestias omnis, pariatur quibusdam, quidem quisquam recusandae
      similique sint vero voluptates voluptatibus? Architecto aspernatur,
      officiis. Aperiam corporis ducimus impedit sequi.
    </p>

    <p>
      Aliquid aperiam asperiores earum enim, error illum numquam obcaecati
      vero. Ab adipisci aliquid autem deserunt dolorem dolorum error impedit
      itaque libero nemo non praesentium quasi quis, quo sunt suscipit totam?
    </p>
  </main>

  <div id="scrollObserver"></div>
</body>
!

CSS 

              
                @property --scroll-percentage {
  syntax: "<length-percentage>";
  inherits: false;
  initial-value: 0;
}

:root {
  font-family: Inter, system-ui, Avenir, Helvetica, Arial, sans-serif;
  line-height: 1.5;
  font-weight: 400;
  color-scheme: light dark;
  color: rgb(255 255 255 / 87%);
  font-synthesis: none;
  text-rendering: optimizelegibility;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  min-height: 100vh;
  margin: 0;
}

main {
  max-width: 60ch;
  margin: 0 auto;
  padding: 1rem;
  color: lightgray;
}

.background {
  background: radial-gradient(
      circle at var(--scroll-percentage) var(--scroll-percentage),
      hsl(0deg 100% 10%),
      transparent 50%
    ),
    radial-gradient(
      circle at calc(100% - var(--scroll-percentage)) var(--scroll-percentage),
      hsl(90deg 100% 10%),
      transparent 50%
    ),
    radial-gradient(
      circle at calc(100% - var(--scroll-percentage))
        calc(100% - var(--scroll-percentage)),
      hsl(180deg 100% 10%),
      transparent 50%
    ),
    radial-gradient(
      circle at var(--scroll-percentage) calc(100% - var(--scroll-percentage)),
      hsl(270deg 100% 10%),
      transparent 50%
    );
  animation: background-position-diagonal;
  animation-duration: 15s;
  animation-iteration-count: infinite;
  animation-direction: alternate;
  animation-timing-function: cubic-bezier(0, 0.25, 1, 0.75);
}

body.scrollable {
  animation-duration: 1ms; /* Firefox requires this to apply the animation */
  animation-timeline: scroll(y root);
  animation-iteration-count: unset;
}

@keyframes background-position-diagonal {
  from {
    --scroll-percentage: 0%;
  }

  to {
    --scroll-percentage: 125%;
  }
}
!

JS 

              
                import lodash from "https://esm.sh/lodash";

let className = "scrollable";
let observer = new ResizeObserver(
  lodash.debounce((entries) => {
    entries.forEach(() => {
      if (document.body.scrollHeight > window.innerHeight * 1.5) {
        document.body.classList.add(className);
      } else {
        document.body.classList.remove(className);
      }
    });
  }, 400)
);
observer.observe(document.querySelector("#scrollObserver"));
!
999px

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