body {
    font-family: 'Segoe UI', sans-serif;
    background-color: #f5f7fa;
    text-align: center;
    padding: 30px;
}
h1 { color: #2c3e50; }
.error { color: red; font-weight: bold; }
.btn {
    display: inline-block;
    padding: 10px 20px;
    margin: 5px;
    border-radius: 8px;
    background-color: #3498db;
    color: white;
    text-decoration: none;
    font-weight: bold;
}
.btn:hover { background-color: #2980b9; }