#back-to-top {
    position: fixed;
    bottom: 40px;
    right: 20px;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: var(--txt-nav-color);
    color: var(--surface-color);
    border: 1px solid var(--surface-color);
    cursor: pointer;
    font-size: 1.5rem;
    z-index: 999;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
    transform: translateY(10px);
    transition: opacity 0.3s ease, transform 0.3s ease;
}

#back-to-top.visible {
    opacity: 1;
    pointer-events: auto;
    transform: translateY(0);
}
  
#back-to-top:hover {
    opacity: 1;
    background: #555;
    color: var(--hover-color);
    border: 1px solid var(--hover-color);
    transition: 0.2s ease-in-out;
}

#back-to-top svg {
    height: 30px;
    position: absolute;
    top: 5px;
    left: 5px;
}