.go-top {
    position: fixed;
    right: 20px;
    bottom: 20px;
    width: 52px;
    height: 52px;
    border-radius: 50%;
    border: none;
    background: #111;
    color: white;
    font-size: 22px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 12px rgba(0, 0, 0, .2);
    opacity: 0;
    pointer-events: none;
    transition: .2s;
    z-index: 999;
}

.go-top.visible {
    opacity: 1;
    pointer-events: auto;
}