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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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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-.

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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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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.

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HTML 

              
                <section id="message">
<h1>Rainbow<br/>Goodness</h1>
<p>So this is currently set to color cycle every 175 seconds, which is the same as 60 seconds per color divided by two, or 30 seconds per color, assuming roygbiv, even though I only programmed Red, Green, and Blue. The timing itself should actually make it so that each color gets its time, as no color should be a rest, anyhow. Arguably I should have done more to get the full rainbow. We hardly touched the luminosity spectrum, although I think some of that does make it in.</p>
<p>The font color looping is based on a Cyan-Magenta-Yellow loop, as the opposite of RGB.</p></section>
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CSS 

              
                    body {
      animation: colorchange 175s linear 1s infinite; /* animation-name followed by duration in seconds*/
         /* you could also use milliseconds (ms) or something like 2.5s */
      -webkit-animation: colorchange 175s linear 0s infinite alternate; /* Chrome and Safari */
    }

    @keyframes colorchange
    {
      0%   {background: red; color: cyan;}
      33%  {background: green; color: magenta;}
      66%  {background: blue; color: yellow;}
      100% {background: red; color: cyan;}
   }

    @-webkit-keyframes colorchange /* Safari and Chrome - necessary duplicate */
    {
      0%   {background: red; color: cyan;}
      33%  {background: green; color: magenta;}
      66%  {background: blue; color: yellow;}
      100% {background: red; color: cyan;}
   }
section {
  width: 33vw;
  margin: 0 auto;
}
#message {
  text-align: center;
  color: inherit;
  opacity: 75%;
  mix-blend-mode: difference;
  font-family: Cooper Black, Helvetica, Arial;
}
h1 {
  font-size: 4.69em;
}
p {
  font-size: 1.6em;
  font-family: Helvetica Neue, Helvetica, Arial;
}
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JS
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999px

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