body {
    margin: 0;
    font-family: Arial, sans-serif;
    height: 100vh;
}

.center {
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.download-btn {
    padding: 18px 40px;
    background: #28a745;
    color: white;
    font-size: 20px;
    text-decoration: none;
    border-radius: 50px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.3);
}

.download-btn:hover {
    background: #218838;
}

.disabled {
    background: gray;
}