*{margin:0;padding:0;box-sizing:border-box}body{font-family:Segoe UI,Tahoma,Geneva,Verdana,sans-serif;background-color:#f5f5f5;display:flex;justify-content:center;align-items:center;height:100vh}#app{text-align:center;background-color:#fff;border-radius:8px;box-shadow:0 2px 4px #0000001a;padding:40px}h1{color:#333;font-size:36px;margin-bottom:10px}h2,h3,button,p{margin-bottom:10px}p{font-size:18px;color:#666;margin-bottom:20px}button{padding:12px 24px;background-color:#007bff;color:#fff;border:none;border-radius:4px;font-size:16px;cursor:pointer;transition:background-color .3s ease}button:hover{background-color:#0056b3}