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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.

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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.

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

Behavior

Auto Save

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Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

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Visit your global Editor Settings.

HTML 

              
                <svg viewBox="45 60 400 320" xmlns="http://www.w3.org/2000/svg">
    <path fill="#fff" d="M 90 210 C 90 180 90 150 90 150 C 150 150 180 150 180 150 C 180 150 300 150 300 150 C 300 150 330 150 390 150 C 390 150 390 180 390 210 C 390 240 390 270 390 270 C 330 270 300 270 300 270 C 300 270 180 270 180 270 C 180 270 150 270 90 270 C 90 270 90 240 90 210" mask="url(#knockout-text)" >
    </path>
    <mask id="knockout-text">
      <rect width="100%" height="100%" fill="#fff" x="0" y="0" />
      <text x="147" y="227" fill="#000">BUTTON</text>
    </mask>
</svg>

<!--- M 90 210 C 90 180 90 150 150 150 C 150 150 180 150 180 150 C 180 150 300 150 300 150 C 300 150 330 150 330 150 C 390 150 390 180 390 210 C 390 240 390 270 330 270 C 330 270 300 270 300 270 C 300 270 180 270 180 270 C 180 270 150 270 150 270 C 90 270 90 240 90 210 --->
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CSS 

              
                @import url("https://fonts.googleapis.com/css?family=Raleway:900");

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    background-image: url(https://images.unsplash.com/photo-1519501025264-65ba15a82390?w=1600);
    background-size: cover;
    background-position: 50% 50%;
    min-height: 100vh;
    font-family: Raleway, serif;

    &:after {
        content: "";
        width: 100%;
        height: 100%;
        position: fixed;
        background: rgba(0, 0, 0, 0.2);
        z-index: 1;
    }
}

svg {
    width: 80vw;
    position: fixed;
    top: 50vh;
    left: 50vw;
    max-width: 430px;
    transform: translateY(-50%) translateX(-50%);
    z-index: 2;
    filter: drop-shadow(0 0 40px rgba(0, 0, 0, 0.3));

    path {
        cursor: pointer;
        animation: blob 2s infinite forwards;
        transform-origin: 50% 50%;

        &:hover {
            fill: #fafafa;
        }
    }

    text {
        font-size: 45px;
    }
}

@keyframes blob {
    25% {
        d: path(
            "M 90 210 C 90 180 110 160 130 160 C 160 160 180 140 200 130 C 230 120 270 100 290 140 C 310 170 340 100 360 140 C 370 160 390 180 390 210 C 390 240 380 290 350 280 C 330 270 300 280 280 290 C 260 300 230 300 220 290 C 200 270 160 310 140 280 C 130 260 90 240 90 210 "
        );
        transform: rotate(-5deg);
    }
    50% {
        d: path(
            "M 90 210 C 90 180 100 150 120 130 C 150 100 180 140 200 130 C 230 120 270 100 290 140 C 300 160 330 130 360 140 C 390 150 390 180 390 210 C 390 240 380 300 350 280 C 330 270 320 230 280 260 C 260 280 220 310 200 290 C 180 270 160 280 140 280 C 110 280 90 240 90 210"
        );
    }
    75% {
        d: path(
            "M 90 210 C 90 180 110 180 130 170 C 150 160 170 130 200 130 C 240 130 260 150 290 140 C 310 130 340 120 360 140 C 380 160 390 180 390 210 C 390 240 380 260 350 270 C 320 280 290 270 270 260 C 240 250 230 280 210 290 C 180 310 130 300 110 280 C 90 260 90 240 90 210"
        );
        transform: rotate(5deg);
    }
}
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JS
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