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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

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.

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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="accordion">
<details>
    <summary>Sesame snaps</summary>
  <div>Sweet roll donut bonbon cheesecake pudding ice cream oat cake chocolate apple pie. Marshmallow sweet roll muffin macaroon donut. Tootsie roll cupcake cotton candy jujubes apple pie apple pie jelly beans. Marshmallow jelly-o marzipan caramels pudding icing toffee lemon drops carrot cake.</div>
</details>
  <details>
    <summary>Chocolate bar</summary>
  <div>Lollipop dessert sweet roll liquorice jelly-o marzipan. Lemon drops icing marshmallow soufflé soufflé. Gingerbread croissant gummi bears brownie chocolate bar pudding.

</div>
</details>
  <details>
    <summary>Donut gummies</summary>
  <div>Halvah muffin toffee bear claw jujubes. Liquorice jelly marzipan toffee macaroon bonbon tootsie roll toffee soufflé. Jelly pie gummies muffin tart soufflé ice cream liquorice apple pie. Sugar plum bear claw chocolate bar croissant bear claw tiramisu topping.</div>
</details>
</div>
!

CSS 

              
                details {
  margin: 5px;
  font-size: 18px;
}
details > * {
  padding: .75rem;
}
summary {
  border-radius: 5px;
  font-size: 20px;
  font-family: sans-serif;
  font-weight: bold;
  color: #fff;
  background: #0B486B;
  cursor: pointer;
  position: relative;
}
summary::marker {
  content: "";
}
summary::before {
  content:"";
  position:absolute;
  inset: .75rem;
  left: auto;
  aspect-ratio: 1;
  background: 
   conic-gradient(from 90deg at 33% 33%, #0000 90deg, #fff 0) 
    100% 100%/60% 60%;
  clip-path: inset(1px);
}
details[open] summary::before {
  background: linear-gradient(#fff 0 0) 50%/100% 25% no-repeat;
}
details[open] summary {
  border-radius: 5px 5px 0 0;
}
details > div {
  background: #ddd;
  border-radius: 0 0 5px 5px;
}
!

JS
!
999px

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