/* --- BOUTON RETOUR EN HAUT --- */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    border-radius: 50%;

    /* Ton dégradé bleu signature */
    background: linear-gradient(135deg, #0d6efd 0%, #0a58ca 100%);
    color: white;

    font-size: 1.5rem;
    z-index: 990; /* Au-dessus du contenu, mais sous la navbar (9999) */

    /* Invisible par défaut */
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);

    transition: all 0.4s cubic-bezier(0.25, 0.8, 0.25, 1);
    box-shadow: 0 5px 15px rgba(13, 110, 253, 0.3);
    text-decoration: none;
}

/* Classe ajoutée par le JS quand on scroll */
.back-to-top.active {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    background: linear-gradient(135deg, #0b5ed7 0%, #084298 100%);
    color: white;
    transform: translateY(-5px); /* Petit saut au survol */
    box-shadow: 0 8px 25px rgba(13, 110, 253, 0.5);
}

/* Responsive Mobile */
@media (max-width: 768px) {
    .back-to-top {
        bottom: 20px;
        right: 20px;
        width: 45px;
        height: 45px;
        font-size: 1.2rem;
    }
}