#scrollTopBtn {
    position: fixed;
    bottom: 28px;
    right: 28px;

    width: 46px;
    height: 46px;

    display: flex;
    align-items: center;
    justify-content: center;

    border-radius: 50%;
    background: rgba(20,24,28,0.85);
    border: 1px solid rgba(255, 255, 255, 0.39);

    color: var(--primary);
    font-size: 1.4rem;

    cursor: pointer;
    z-index: 9999;

    opacity: 0;
    pointer-events: none;
    transform: translateY(20px);

    transition:
        opacity 0.35s ease,
        transform 0.35s ease,
        background 0.25s ease,
        box-shadow 0.25s ease,
        border-color 0.25s ease;
}

#scrollTopBtn.visible {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
}

#scrollTopBtn:hover {
    background: rgba(10,170,181,0.15);
    border-color: var(--primary);
    box-shadow:
        0 0 0 1px rgba(10,170,181,0.25),
        0 10px 30px rgba(0,0,0,0.45);
}