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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>

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

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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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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 

              
                <a href="#" class="link-5">STEAM 教育學習網</a> ( hover + 漸層色偽裝底線 + 轉場 )</body>
<br>
<a href="#" class="link-6">STEAM 教育學習網</a> ( hover + 漸層色背景動畫 )</body>
!

CSS 

              
                body {line-height: 2;}
a[class] {color: blue;}        /* 有 class 的超連結文字為藍色 */
a[class]:hover {color: red;}  /* 有 class 的超連結 hover 時文字為紅色 */

/* 建立自訂屬性 --c，類型為顏色 */
@property --c {
  syntax: "<color>";
  inherits: true;
  initial-value: blue;
}
/* 建立自訂屬性 --y，類型為長度 */
@property --y {
  syntax: "<length>";
  inherits: true;
  initial-value: 2px;
}

.link-5 {
  line-height: 1.3;
  display:inline-block;                   /* 改成 inline-block 顯示類型，才能控制尺寸 */
  text-decoration: none;                  /* 隱藏底線 */
  transition: all .5s, --c .5s, --y .5s;  /* 將自訂屬性套用轉場效果 */
  /* 背景漸層色中使用自訂屬性 */
  background: linear-gradient(0deg, 
    var(--c) 0, 
    var(--c) 2px, 
    #0000 var(--y), 
    #0000 100%);
}
/* hover 時改變自訂屬性 */
.link-5:hover {
  --c: red;
  --y: 15px;
}

/* 建立自訂屬性 --dx，類型為長度 */
@property --dx {
  syntax: "<length>";
  inherits: true;
  initial-value: 0;
}
.link-6 {
  line-height: 1.3;
  display: inline-block;   /* 改成 inline-block 顯示類型，才能控制尺寸 */
}
.link-6:hover {
  text-decoration: none;   /* 隱藏底線 */
  /* 漸層色中使用自訂屬性 */
  background: repeating-linear-gradient(
      to right,
      pink calc(var(--dx)),  pink calc(10px + var(--dx)),
      #0000 calc(10px + var(--dx)), #0000 calc(20px + var(--dx)));
  /* 執行動畫 */
  animation: oxxo 1s linear infinite;
}
/* 動畫中改變自訂屬性 */
@keyframes oxxo {
  0% {--dx: 0;}
  100% {--dx: 20px;}
}
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JS
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999px

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