body {
    background: #f4f8fc;
}
.card {
    max-width: 500px;
    margin: 0 auto;
    border-radius: 1rem;
}
#qrResult img {
    max-width: 100%;
    margin-bottom: 1rem;
    background: #fff;
    padding: 10px;
    border-radius: 1rem;
    box-shadow: 0 4px 20px rgba(0,0,0,0.07);
}
@media (max-width: 767px) {
    .row.justify-content-center {
        flex-direction: column;
    }
    #qrResult {
        margin-top: 24px;
    }
}