HTML Code

<!DOCTYPE html>
<html>
<head>
  <title>CSS * box-sizing Example</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    body {
      font-family: system-ui, sans-serif;
      padding: 1.5rem;
      color: #334155;
    }

    .box {
      width: 200px;
      padding: 20px;
      border: 2px solid #2563eb;
      border-radius: 0.4rem;
      background: #eff6ff;
      font-size: 0.875rem;
    }
  </style>
</head>
<body>
  <div class="box">Total width is 200px including padding and border.</div>
</body>
</html>

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CSS * Selector - box-sizing Reset