.back-bubble {
    position: fixed;
    bottom: 20px;        /* ✅ desktop default */
    left: 10px;

    background-color: #4eae54;
    color: white;
    font-size: 1.5rem;
    padding: 10px 15px;
    border-radius: 50%;
    z-index: 1000;
    text-decoration: none;
    box-shadow: 0 4px 8px rgba(0,0,0,0.3);
    transition: all 0.2s ease;
}

.back-bubble:hover {
    background-color: #d3dadf;
}

/* 📱 Mobile override */
@media (max-width: 768px) {
    .back-bubble {
        top: calc(70px + env(safe-area-inset-top)); /* below navbar */
        bottom: auto; /* ❗ critical fix */
        font-size: 1.25rem;
        padding: 8px 12px;
    }
}