.btn-top {
    position: fixed;
    right: 30px;
    bottom: 30px;
    z-index: 20;
    width: 44px;
    height: 44px;
    border: none;
    border-radius: 50%;
    background: rgba(0, 0, 0, 0.4);
    color: #fff;
    font-size: 18px;
    cursor: pointer;
}

.btn-top:hover {
    background: rgba(0, 0, 0, 0.6);
}