.scroll-top-btn {
    position: fixed;
    right: 24px;
    bottom: 24px;
    width: 48px;
    height: 48px;
    border: 0;
    border-radius: 50%;
    background: linear-gradient(135deg, #178f95, #2fb779);
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    box-shadow: 0 14px 28px rgba(23, 143, 149, 0.28);
    opacity: 0;
    visibility: hidden;
    transform: translateY(14px);
    transition: opacity 0.25s ease, visibility 0.25s ease, transform 0.25s ease, box-shadow 0.25s ease;
    z-index: 99999;
}

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

.scroll-top-btn:hover {
    box-shadow: 0 18px 34px rgba(23, 143, 149, 0.36);
}

.scroll-top-btn span {
    font-size: 1.8rem;
    font-weight: 800;
    line-height: 1;
}

@media (max-width: 600px) {
    .scroll-top-btn {
        right: 16px;
        bottom: 16px;
        width: 44px;
        height: 44px;
    }
}