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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.

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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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About External Resources

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.

You can also link to another Pen here (use the .css URL Extension) and we'll pull the CSS from that Pen and include it. If it's using a matching preprocessor, use the appropriate URL Extension and we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.

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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

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

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About External Resources

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.

Learn more

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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 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.

If you're using React / ReactDOM, make sure to turn on Babel for the JSX processing.

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HTML 

              
                <body id="top">
  <header>
    <a class="round-button wizard tooltip" href="https://www.osedea.com/en/blog/8-css-wizard-spells" target="_blank" aria-label="Go to article">
      <span class="ignore-dark-theme">
        🧙
      </span>
    </a>
    <button type="button" class="theme-toggle round-button tooltip left" onclick="toggleTheme()" aria-label="Switch to dark theme">
      <svg class="sun" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-sun"><circle cx="12" cy="12" r="5"></circle><line x1="12" y1="1" x2="12" y2="3"></line><line x1="12" y1="21" x2="12" y2="23"></line><line x1="4.22" y1="4.22" x2="5.64" y2="5.64"></line><line x1="18.36" y1="18.36" x2="19.78" y2="19.78"></line><line x1="1" y1="12" x2="3" y2="12"></line><line x1="21" y1="12" x2="23" y2="12"></line><line x1="4.22" y1="19.78" x2="5.64" y2="18.36"></line><line x1="18.36" y1="5.64" x2="19.78" y2="4.22"></line></svg>
      <svg class="moon" xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-moon"><path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"></path></svg>
    </button>
    <a href="#bottom" class="round-button tooltip left" aria-label="Scroll to bottom">
      <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-arrow-down"><line x1="12" y1="5" x2="12" y2="19"></line><polyline points="19 12 12 19 5 12"></polyline></svg>
    </a>
  </header>
  <main>
    <div class="grid">
      <a class="card">
        <h4 class="title truncate">The Nightmare Before Christmas</h4>
        <p class="description line-clamp">
          Jack Skellington, king of Halloween Town, discovers Christmas Town, but his
          attempts to bring Christmas to his home causes confusion.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">The Silence of the Lambs</h4>
        <p class="description line-clamp">
          A young F.B.I. cadet must receive the help of an incarcerated and manipulative
          cannibal killer to help catch another serial killer, a madman who skins his
          victims. Jack Skellington, king of Halloween Town, discovers Christmas Town, but
          his attempts to bring Christmas to his home causes confusion.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Hotel Transylvania</h4>
        <p class="description line-clamp">
          Dracula, who operates a high-end resort away from the human world, goes into
          overprotective mode when a boy discovers the resort and falls for the count's
          teenaged daughter.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Coraline</h4>
        <p class="description line-clamp">
          An adventurous 11-year-old girl finds another world that is a strangely
          idealized version of her frustrating home, but it has sinister secrets.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Sleepy Hollow</h4>
        <p class="description line-clamp">
          Ichabod Crane is sent to Sleepy Hollow to investigate the decapitations of three
          people, with the culprit being the legendary apparition, The Headless Horseman.
          An adventurous 11-year-old girl finds another world that is a strangely
          idealized version of her frustrating home, but it has sinister secrets.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Ghostbusters</h4>
        <p class="description line-clamp">
          Three former parapsychology professors set up shop as a unique ghost removal
          service.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">The Shining</h4>
        <p class="description line-clamp">
          A family heads to an isolated hotel for the winter where a sinister presence
          influences the father into violence, while his psychic son sees horrific
          forebodings from both past and future.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">The Addams Family</h4>
        <p class="description line-clamp">
          Con artists plan to fleece an eccentric family using an accomplice who claims to
          be their long-lost uncle.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Psycho</h4>
        <p class="description line-clamp">
          A Phoenix secretary embezzles $40,000 from her employer's client, goes on the
          run, and checks into a remote motel run by a young man under the domination of
          his mother.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">The Witches</h4>
        <p class="description line-clamp">
          Based on Roald Dahl's 1983 classic book 'The Witches', the story tells the scary, funny and imaginative tale of a seven year old boy who has a run in with some real life witches!
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Poltergeist</h4>
        <p class="description line-clamp">
          A family's home is haunted by a host of demonic ghosts.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">The Conjuring</h4>
        <p class="description line-clamp">
          Paranormal investigators Ed and Lorraine Warren work to help a family terrorized by a dark presence in their farmhouse.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">A Nightmare on Elm Street</h4>
        <p class="description line-clamp">
          The monstrous spirit of a slain child murderer seeks revenge by invading the dreams of teenagers whose parents were responsible for his untimely death.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Practical Magic</h4>
        <p class="description line-clamp">
          Two witch sisters, raised by their eccentric aunts in a small town, face closed-minded prejudice and a curse which threatens to prevent them ever finding lasting love.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">The Craft</h4>
        <p class="description line-clamp">
          A newcomer to a Catholic prep high school falls in with a trio of outcast teenage girls who practice witchcraft, and they all soon conjure up various spells and curses against those who anger them.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">The Sixth Sense</h4>
        <p class="description line-clamp">
          A boy who communicates with spirits seeks the help of a disheartened child psychologist.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">A Quiet Place</h4>
        <p class="description line-clamp">
          In a post-apocalyptic world, a family is forced to live in silence while hiding from monsters with ultra-sensitive hearing.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Paranormal Activity</h4>
        <p class="description line-clamp">
          After moving into a suburban home, a couple becomes increasingly disturbed by a nightly demonic presence.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Monster House</h4>
        <p class="description line-clamp">
          Three teens discover that their neighbor's house is really a living, breathing, scary monster.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Hereditary</h4>
        <p class="description line-clamp">
          A grieving family is haunted by tragic and disturbing occurrences.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Us</h4>
        <p class="description line-clamp">
          A family's serene beach vacation turns to chaos when their doppelgängers appear and begin to terrorize them.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">The Haunted Mansion</h4>
        <p class="description line-clamp">
          A realtor and his wife and children are summoned to a mansion, which they soon discover is haunted, and while they attempt to escape, he learns an important lesson about the family he has neglected.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Halloween</h4>
        <p class="description line-clamp">
          Laurie Strode confronts her long-time foe Michael Myers, the masked figure who has haunted her since she narrowly escaped his killing spree on Halloween night four decades ago.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">The Amityville Horror</h4>
        <p class="description line-clamp">
          Newlyweds are terrorized by demonic forces after moving into a large house that was the site of a grisly mass murder a year before.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Ernest Scared Stupid</h4>
        <p class="description line-clamp">
          Ernest accidentally unleashes an ugly troll that plots to transform children into wooden dolls in the town of Briarville, Missouri.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Get Out</h4>
        <p class="description line-clamp">
          A young African-American visits his white girlfriend's parents for the weekend, where his simmering uneasiness about their reception of him eventually reaches a boiling point.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">It</h4>
        <p class="description line-clamp">
          In the summer of 1989, a group of bullied kids band together to destroy a shape-shifting monster, which disguises itself as a clown and preys on the children of Derry, their small Maine town.
        </p>
      </a>
      <a class="card">
        <h4 class="title truncate">Beetlejuice</h4>
        <p class="description line-clamp">
          The spirits of a deceased couple are harassed by an unbearable family that has moved into their home, and hire a malicious spirit to drive them out.
        </p>
      </a>
    </div>
  </main>
  <footer id="bottom">
    <a href="#top" class="round-button tooltip left" aria-label="Scroll to top">
      <svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" class="feather feather-arrow-up"><line x1="12" y1="19" x2="12" y2="5"></line><polyline points="5 12 12 5 19 12"></polyline></svg>
    </a>
  </footer>
</body>
!

CSS 

              
                /* Demo CSS */
:root {
  --background-color: #ececec;
  --text-color: #353535;
}
body {
  font-family: 'Merriweather', serif;
  color: var(--text-color);
  background-color: var(--background-color);
  max-width: 1024px;
  margin: 0 auto;
  padding: 1rem;
}
header {
  margin: 2rem 0 3rem 0;
  display: flex;
  align-items: center;
  position: relative;
  z-index: 10;
}
header > * + * {
  margin-left: 1rem;
}
footer {
  margin: 3rem 0;
  display: flex;
  align-items: center;
  justify-content: flex-end;
}
.wizard {
  font-size: 1.5rem;
  line-height: 1;
  margin-right: auto;
}
.round-button {
  color: inherit;
  appearance: none;
  border: none;
  outline: none;
  cursor: pointer;
  text-decoration: none;
  background: var(--background-color);
  border-radius: 3rem;
  width: 3rem;
  height: 3rem;
  display: flex;
  align-items: center;
  justify-content: center;
}
.card {
  padding: 1rem;
  background-color: #ffffff;
  border-radius: 0.25rem;
}
.card .title {
  margin: 0;
  font-size: 1.25rem;
  color: #252525;
}
.card .description {
  margin: 0;
  font-size: 0.875rem;
}
.theme-toggle .sun {
  display: none;
}
.dark-theme .theme-toggle .sun {
  display: block;
}
.dark-theme .theme-toggle .moon {
  display: none;
}

/* 1. Instant fluid grid layout */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr));
  grid-gap: 1rem;
}

/* 2. Truncate strings so they fit on one line */
.truncate {
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* 3. Truncate text to a specific number of lines */
.line-clamp {
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

/* 4. Instant dark theme */
.dark-theme,
.dark-theme img,
.dark-theme .ignore-dark-theme {
  filter: invert(1) hue-rotate(180deg);
}

/* 5. Smooth scroll */
html {
  scroll-behavior: smooth;
}

/* 6. Sticky header */
header {
  position: sticky;
  top: 1rem;
}


/* 7. Easy hover and active states */
button:hover,
a:hover {
  filter: brightness(0.9);
}
button:active,
a:active {
  filter: brightness(0.85);
}

/* 8. Pure CSS tooltips */
.tooltip {
  position: relative;
}
.tooltip:hover::before {
  opacity: 1;
}
.tooltip::before {
  opacity: 0;
  display: block;
  content: attr(aria-label);
  background-color: #353535;
  color: white;
  font-family: Arial, Helvetica, sans-serif;
  font-size: 0.875rem;
  text-decoration: none;
  white-space: nowrap;
  padding: 0.5rem;
  border-radius: 0.25rem;
  pointer-events: none;
  position: absolute;
  top: 80%;
  left: 80%;
}
.tooltip.left::before {
  left: auto;
  right: 80%;
}
!

JS 

              
                const toggleTheme = () => {
  if (document.documentElement.classList.contains('dark-theme')) {
    document.documentElement.classList.remove('dark-theme');
    document.querySelector('.theme-toggle').setAttribute('aria-label', 'Switch to light theme');
  } else {
    document.documentElement.classList.add('dark-theme');
    document.querySelector('.theme-toggle').setAttribute('aria-label', 'Switch to dark theme');
  }
}
!
999px

Console