body {
    background-color: #f5f5f5;
}
.card-header {
    background-color: #343a40;
    color: white;
}
.card-header h5 {
    margin-bottom: 0;
}
.font-monospace {
    letter-spacing: 0.3em;
    font-size: 2rem;
}
#qr-image {
    border: 4px solid #25D366;
    border-radius: 8px;
}