#backtotop {
    position: fixed;
    bottom: 30px;
    right: 30px;
    background-color: #555;
    color: white;
    width: 48px;
    height: 48px;
    padding: 0;
    border-radius: 50%;
    line-height: 48px;
    text-align: center;
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.875rem; /* 30px */
    font-weight: bold;
    font-family: Arial, sans-serif;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
    z-index: 999;
}

#backtotop.show {
    opacity: 0.8;
    pointer-events: auto;
}

#backtotop:hover {
    opacity: 1;
}