index.html HTML5 / CSS3

<!DOCTYPE html>
<html lang="en">
<head>
  <style>
    body {
      font-family: 'Segoe UI', system-ui, sans-serif;
      background: linear-gradient(135deg, #111827, #1f2937);
      color: #f9fafb;
      display: flex;
      justify-content: center;
      align-items: center;
      min-height: 100vh;
      margin: 0;
    }
    .card {
      background: #1f2937;
      border: 1px solid #374151;
      padding: 32px;
      border-radius: 16px;
      text-align: center;
      box-shadow: 0 10px 25px rgba(0,0,0,0.5);
      max-width: 320px;
    }
    h1 { color: #f97316; margin-bottom: 8px; font-size: 1.5rem; }
    p { color: #9ca3af; font-size: 0.95rem; margin-bottom: 20px; }
    button {
      background: #f97316;
      color: #fff;
      border: none;
      padding: 10px 20px;
      font-weight: 600;
      border-radius: 8px;
      cursor: pointer;
      transition: background 0.2s;
    }
    button:hover { background: #ea580c; }
  </style>
</head>
<body>
  <div class="card">
    <h1>Hello, World! 🚀</h1>
    <p>Interactive HTML & CSS live preview inside your browser.</p>
    <button onclick="showMessage()">Click Me</button>
  </div>

Live Rendered

⚡ Console output logs will appear here.