HTML-CSS-Project/chapter21.html at main · TulyXPlatform/HTML-CSS-Project · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Chapter 21: Advanced CSS</title>
  <link rel="stylesheet" href="style.css">
  <style>
    /* CSS Variables */
    :root {
      --a-global-color: red;
    }
    .variable-demo {
      --a-local-color: blue;
      border: 1px solid #ccc;
      padding: 10px;
      margin: 5px 0;
    }
    .variable-demo .demo-header {
      color: var(--a-global-color);
      font-weight: bold;
    }
    .variable-demo .demo-footer {
      color: var(--a-local-color);
      font-style: italic;
    }
    .main-footer {
      color: gray;
      margin-top: 5px;
    }

    /* CSS Calculation */
    .calc-box {
      border: 1px solid #999;
      margin: 5px 0;
    }
    .calc-header, .calc-footer {
      height: 30px;
      line-height: 30px;
      text-align: center;
      font-weight: bold;
    }
    .calc-header {
      border-bottom: 1px solid black;
    }
    .calc-footer {
      border-top: 1px solid black;
    }
    .calc-content {
      min-height: calc(200px - 60px); /* compact */
      padding: 10px;
    }
    .long-content {
      border: 1px solid #ccc;
      padding: 5px;
      margin-top: 10px;
    }

    /* CSS Counters */
    .counter-demo {
      font-size: 14px;
      counter-reset: my-section;
      border: 1px dashed #aaa;
      padding: 10px;
      margin: 5px 0;
    }
    .counter-demo h3 {
      counter-reset: my-sub-section;
      margin-top: 10px;
    }
    .counter-demo h3::before {
      counter-increment: my-section;
      content: "Section " counter(my-section) ". ";
      font-weight: bold;
      color: darkred;
    }
    .counter-demo h4::before {
      counter-increment: my-sub-section;
      content: counter(my-section) "." counter(my-sub-section) " ";
      color: darkblue;
      margin-right: 5px;
    }
  </style>
</head>
<body>
  <h2 class="chapter-header" id="heading">Chapter 21: Advanced CSS</h2>

  <div class="tag-section">
    <h3>1.1 CSS Variables</h3>
    <div class="tag-demo">
      <div class="head-demo">
        <div class="variable-demo">
          <div class="demo-header">This is a heading (red - global variable)</div>
          <p>This is a normal paragraph.</p>
          <div class="demo-footer">This is a section footer (blue - local variable).</div>
        </div>
        <div class="main-footer">This is the main footer (cannot access local variable).</div>
      </div>
    </div>
  </div>

  <div class="tag-section">
    <h3>1.2 CSS Calculation</h3>
    <div class="tag-demo">
      <div class="head-demo">
        <div class="calc-box">
          <div class="calc-header">Header</div>
          <div class="calc-content">
            <p>This is a paragraph.</p>
            <p class="long-content">Resize the container to see footer behavior.</p>
          </div>
          <div class="calc-footer">Footer</div>
        </div>
      </div>
    </div>
  </div>

  <div class="tag-section">
    <h3>1.3 CSS Counters</h3>
    <div class="tag-demo">
      <div class="head-demo">
        <div class="counter-demo">
          <h3>HTML tutorials:</h3>
          <h4>HTML Tutorial</h4>
          <h4>CSS Tutorial</h4>
          <h3>Scripting tutorials:</h3>
          <h4>JavaScript</h4>
          <h4>VBScript</h4>
        </div>
      </div>
    </div>
  </div>
</body>
</html>