introduction-to-css.html

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  <title>1. Introduction to CSS</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }
    body, html {
      height: 100%;
      font-family: 'Poppins', sans-serif;
      overflow-x: hidden;
      background-color: #1cc9be;
    }
    .section {
      background-color: rgba(255, 255, 255, 0.3);
      margin: 20px auto;
      padding: 20px;
      border-radius: 12px;
      width: 90%;
      max-width: 1000px;
      box-shadow: 0 8px 16px rgba(0,0,0,0.3);
    }
    h2, h3 {
      color: #333;
      margin-bottom: 15px;
    }
    p {
      font-size: 18px;
      margin-bottom: 20px;
      line-height: 1.7;
    }
    textarea {
      width: 100%;
      height: 150px;
      font-family: monospace;
      font-size: 16px;
      padding: 10px;
      border: 2px solid white;
      border-radius: 8px;
      margin-top: 10px;
      margin-bottom: 10px;
      background: rgba(255,248,240,0.4);
    }
    button {
      background-color: #28a745;
      color: white;
      border: none;
      padding: 10px 20px;
      font-size: 16px;
      border-radius: 8px;
      cursor: pointer;
      margin-bottom: 20px;
    }
    iframe {
      width: 100%;
      height: 150px;
      background: rgba(255,248,240,0.4);
      border: 2px solid white;
      border-radius: 8px;
      margin-top: 15px;
    }
  </style>
</head>
<body>

<div class="section">
  <h2>1. Introduction to CSS</h2>

  <h3>I. What is CSS?</h3>
  <p><strong>Explanation:</strong> CSS ka full form hai <em>Cascading Style Sheets</em>. Ye HTML elements ko style dene ke liye use hota hai — jaise colors, layout, spacing, fonts wagairah.</p>

  <textarea id="css1">
<!DOCTYPE html>
<html>
<head>
  <style>
    h1 {
      color: darkblue;
      font-size: 40px;
    }
    p {
      color: #555;
    }
  </style>
</head>
<body>
  <h1>Hello CSS</h1>
  <p>This is styled with CSS.</p>
</body>
</html>
  </textarea>
  <button onclick="runCode('css1', 'output1')">Run Code</button>
  <iframe id="output1"></iframe>


  <h3>II. CSS Syntax</h3>
  <p><strong>Explanation:</strong> CSS syntax me 2 main parts hote hain — <code>selector</code> aur <code>declaration block</code>. Dekho:</p>

  <textarea id="css2">
/* Syntax */
selector {
  property: value;
}

/* Example */
p {
  color: red;
  font-size: 18px;
}
  </textarea>
  <button onclick="runCode('css2', 'output2')">Run Code</button>
  <iframe id="output2"></iframe>


  <h3>III. Types of CSS</h3>
  <p><strong>Explanation:</strong>
    <ul>
      <li><strong>Inline CSS:</strong> Direct element ke andar style dena.</li>
      <li><strong>Internal CSS:</strong> <code>&lt;style&gt;</code> tag ke andar likhna (head ke andar).</li>
      <li><strong>External CSS:</strong> Alag file me likhkar link karna.</li>
    </ul>
  </p>

  <textarea id="css3">
<!-- Internal CSS Example -->
<!DOCTYPE html>
<html>
<head>
  <style>
    h2 {
      color: green;
    }
  </style>
</head>
<body>
  <h2>Internal CSS Example</h2>
</body>
</html>
  </textarea>
  <button onclick="runCode('css3', 'output3')">Run Code</button>
  <iframe id="output3"></iframe>

</div>

<script>
function runCode(textareaId, iframeId) {
  const code = document.getElementById(textareaId).value;
  const iframe = document.getElementById(iframeId);
  iframe.contentDocument.open();
  iframe.contentDocument.write(code);
  iframe.contentDocument.close();
}
</script>

</body>
</html>