/*¤@Á䩹¤W*/
.back-to-top {
    position: fixed;
    bottom: 20px;
    right: 25px;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background: rgba(175, 183, 193, 0.7);
    visibility: hidden;
    cursor: pointer;
    -webkit-transition: all .2s ease;
    transition: all .2s ease;
    z-index: 1100;
}

    .back-to-top::after {
        content: "";
        position: absolute;
        top: 50%;
        left: 0;
        right: 0;
        margin: -4px auto;
        width: 12px;
        height: 12px;
        border-top: 2px solid #555;
        border-right: 2px solid #555;
        -webkit-transform: rotate(-45deg);
        transform: rotate(-45deg);
    }

    .back-to-top:hover {
        background: #2F89FC;
    }

        .back-to-top:hover::after {
            border-color: #fff;
        }