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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>

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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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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
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CSS 

              
                html {	
	--u: 1.185vmin;
	--hue: hue-rotate(0deg);
	--c1: #000000;
	--c2: #9a1f22;
	--c3: #e35e13;
	--gp: 50%/calc(var(--u) * 12) calc(var(--u) * 17.05);
	height: 100vh;
	filter: var(--hue);
	background: 
		conic-gradient(from 0deg at 13.68% 94.08%, #fff0 0 50%, var(--c2) 0% 83.33%, #fff0 0 100%)  var(--gp),  /* left red end */
		conic-gradient(from 0deg at 86.12% 94.08%, #fff0 0 16.66%, var(--c2) 0% 50%, #fff0 0 100%)  var(--gp),  /* right red end */
		conic-gradient(from 0deg at 28.42% 88.14%, #fff0 0 50%, var(--c1) 0% 83.33%, #fff0 0 100%)  var(--gp),  /* left black end */
		conic-gradient(from 0deg at 71.57% 88.14%, #fff0 0 16.66%, var(--c1) 0% 50%, #fff0 0 100%)  var(--gp),  /* right black end */
		conic-gradient(from 0deg at 7.36% 43.70%, #fff0 0 50%, var(--c1) 0% 75%, #fff0 0 100%)  var(--gp),  /* left black vert*/
		conic-gradient(from 0deg at 92.64% 43.70%, #fff0 0 25%, var(--c1) 0% 50%, #fff0 0 100%)  var(--gp),  /* right black vert */
		conic-gradient(from 0deg at 43.15% 82.22%, #fff0 0 50%, var(--c3) 0% 83.33%, #fff0 0 100%)  var(--gp),  /* left orange end */
		conic-gradient(from 0deg at 56.84% 82.22%, #fff0 0 16.66%, var(--c3) 0% 50%, #fff0 0 100%)  var(--gp),  /* right orange end */
		conic-gradient(from 0deg at 23.15% 50.37%, #fff0 0 50%, var(--c3) 0% 75%, #fff0 0 100%)  var(--gp),  /* left orange vert */
		conic-gradient(from 0deg at 76.85% 50.37%, #fff0 0 25%, var(--c3) 0% 50%, #fff0 0 100%)  var(--gp),  /* right orange vert */
		conic-gradient(from 0deg at 50% 73.33%, #fff0 0 16.66%, var(--c1) 0% 83.33%, #fff0 0 100%)  var(--gp),  /* middle black */
		conic-gradient(from 0deg at 36.84% 56.29%, #fff0 0 50%, var(--c1) 0% 75%, #fff0 0 100%)  var(--gp),  /* left black middle */
		conic-gradient(from 0deg at 63.15% 56.29%, #fff0 0 25%, var(--c1) 0% 50%, #fff0 0 100%)  var(--gp),  /* right black middle*/
		conic-gradient(from 0deg at 50% 51.11%, #fff0 0 33.33%, var(--c2) 0% 66.66%, #fff0 0 100%)  var(--gp),  /* middle red */
		conic-gradient(from 0deg at 50% 39.25%, #fff0 0 33.33%, var(--c1) 0% 66.66%, #fff0 0 100%)  var(--gp),  /* middle black */
		conic-gradient(from 0deg at 50% 26.66%, #fff0 0 33.33%, var(--c3) 0% 66.66%, #fff0 0 100%)  var(--gp),  /* middle orange */
		conic-gradient(from 0deg at 13.68% 5.92%, #fff0 0 66.66%, var(--c2) 0% 100%)  var(--gp),  /* left red top */
		conic-gradient(from 0deg at 86.12% 5.92%, var(--c2) 0 33.33%, #fff0 0% 100%) var(--gp),   /* right red top */
		conic-gradient(from 0deg at 28.42% 11.85%, #fff0 0 66.66%, var(--c1) 0% 100%)  var(--gp),  /* left black top */
		conic-gradient(from 0deg at 71.58% 11.85%, var(--c1) 0 33.33%, #fff0 0% 100%) var(--gp),   /* right black top */
		conic-gradient(from 0deg at 43.15% 17.77%, #fff0 0 66.66%, var(--c3) 0% 100%)  var(--gp), /* left orange top */
		conic-gradient(from 0deg at 56.84% 17.77%, var(--c3) 0 33.33%, #fff0 0% 100%) var(--gp)   /* right orange top*/
		;
    background-color: var(--c1);
}
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JS
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