.btn-back-top {
    position: fixed;
    right: 20px;
    bottom: 55px;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: #121a77;
    color: #fff;
    font-size: 22px;
    display: flex;
    justify-content: center;
    align-items: center;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.25);
    cursor: pointer;
    z-index: 9999;
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: all 0.4s ease;
}

.btn-back-top.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

/*  Hover (solo escritorio) */
.btn-back-top:hover {
    background-color: #e36414;
    transform: scale(1.1);
}

@media (max-width: 576px) {
    .btn-back-top {
        bottom: 55px; /*  justo sobre el copyright */
        right: 15px;
        width: 45px;
        height: 45px;
        font-size: 20px;
    }
}