/* Современная кнопка "Вернуться в начало" */
.back-to-top-btn {
    position: fixed;
    bottom: 30px;
    right: 30px;
    background: rgba(24, 191, 239, 0.9);
    color: #ffffff;
    border: none;
    border-radius: 50%;
    width: 56px;
    height: 56px;
    cursor: pointer;
    font-size: 1.2rem;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    opacity: 0;
    visibility: hidden;
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 12px rgba(24, 191, 239, 0.3), 0 2px 4px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
}

.back-to-top-btn.show {
    opacity: 1;
    visibility: visible;
}

.back-to-top-btn:hover {
    background: rgba(24, 191, 239, 1);
    transform: translateY(-2px) scale(1.05);
    box-shadow: 0 8px 20px rgba(24, 191, 239, 0.4), 0 4px 8px rgba(0, 0, 0, 0.2);
}

.back-to-top-btn:active {
    transform: translateY(0) scale(0.95);
    transition: all 0.1s ease;
}

@media (max-width: 768px) {
    .back-to-top-btn {
        bottom: 20px;
        right: 20px;
        width: 48px;
        height: 48px;
        font-size: 1.1rem;
    }
}

/* Анимация появления */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.back-to-top-btn.show {
    animation: fadeInUp 0.3s ease-out;
}