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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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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.

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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

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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 

              
                <div class="card">大家都知道，CSS只是一个声明式的语言，主要为标记语言服务。很多程序员鄙视它，有一部分原因是CSS并不像其他程序语言一样，具有一些逻辑能力以及函数功能等特性。随着CSS的不断变革，其慢慢地也变得越来越强大。</div>
<div class="card">变量对于CSS而言是这两年大家关注的一个话题。对于变量而言，最早是出于CSS的一些处理器语言当中，比如Sass、LESS之类的。随着CSS的发展，变量的概念也被引入到CSS中。</div>
<div class="card">用户界面是最直观的呈现给用户，而其中动画在这方面又扮演着重要的角色。正如@Nick Babich所说:动画将用户界面带入生活。而且，UI动画在用户体验方面也是重要的一环。</div>
<div class="card">今年花了不少的时间在学习DOM相关的知识，经过这段时间的学习，可以通过一些JavaScript的API操作和处理Web页面上的HTML元素。在Web中除了DOM之外还有另外一个对象模型：CSS对象模型（即CSSOM）。</div>
<div class="card">在Web页面或应用程序中都可能会有按钮的出现，甚至很多时候链接的样式看起来也像个按钮。那么我们应该怎么来美化按钮的样式呢？在这篇文章中，我们一起来聊聊按钮样式应该怎么才能更好的控制。</div>
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CSS 

              
                $gap: .75em;
$r: 50vh;

* {
	margin: 0;
	padding: 0;
	box-sizing: border-box;
}
body {
	width: 100vw;
	min-height: 100vh;
	display: flex;
	justify-content: flex-start;
	align-items: center;
	flex-direction: column;
}

.card {
	// 设置数字顺序的关开 --i
	// 当--p有效时，采用--p的值，否则采用回退值0
	--i: var(--p, 0);
	// 当 --i = 0 => --j = 1
	// 当 --i = 1 => --j = 0
	--j: calc(1 - var(--i));
	
	// --i = 0 => 1 - 2 * 0 = 1 - 0 = 1
  // --i = 1 => 1 - 2 * 1 = 1 - 2 = -1
  --s: calc(1 - 2 * var(--i));

  // 给渐变色设置一个自定义属性
  --color-list: #ccc, #f90;
	
	// 圆角半径
	// --i = 0 => --j = 1, --r0 = $r, --r1 = 0
	// --i = 1 => --j = 0, --r0 = 0, --r1 = $r
  // --wide 未显式设置值时 --wide = 0
	// --wide 显式设置值是，将采用设置的值，比如 1
	--k: var(--wide, 0);
	--r0: calc(var(--k) * var(--j) * #{$r});
  --r1: calc(var(--k) * var(--i) * #{$r});
	
	// 宽屏和窄屏的切换
  --k: var(--wide, 0);

    
	
	box-sizing: border-box;
	margin: 2em auto;
	// border: solid 2px #f90;
	padding: .75em;
	max-width: 35rem; 
	width: 80%;
	
	
	counter-increment: count;
	
	display: flex;
  align-items: center;
	
	background: linear-gradient(
		calc(var(--s) * 90deg),
		var(--color-list)
	);
	
	transform: translate(calc(var(--k) * var(--s) * 10%))
               rotate(calc(var(--k) * var(--s) * 5deg));
  flex-direction: var(--wide, column);
  font: 900 calc(var(--k) * .5em + .75em) segoe script, comic sans ms, cursive;
	
	border-radius: var(--r0) var(--r1) var(--r1) var(--r0);
	
	text-align: var(--p, right);
	
	
	&:nth-child(2n) {
		--p: 1;
	}

  &::before {
		font-size: 2em;
  	content: counter(count, decimal-leading-zero);
		// --i等于0，开关关闭，数字的顺序为 order=0
		// --i等于1，开关打开，数字的顺序为 order=1
		order: calc(var(--k) * var(--i));
		
		// 当 --i = 0 => margin-left = 0; --j = 1; margin-right = $gap
		// 当 --i = 1 => margin-left = $gap; --j = 0; margin-right = 0
		margin-left: calc(var(--k) * var(--i) * #{$gap});
    margin-right: calc(var(--k) * var(--j) * #{$gap});
  }
	
	
	@media (min-width: 340px) {
  	--wide: 1
  }
	
}
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JS
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