body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-color: #f0f2f5;
    text-align: center;
}
header {
    background: white;
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}
button {
    padding: 10px 20px;
    background-color: #0070f3;
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}