.menu-scroll {
    width: 100%;
    height: 35px;
    font-size: 24px;
    background: #40444D;
    color: #fff;
    position: absolute;
    text-align: center;
    border: 0;
    z-index: 1020;
    display: none;
}

/* up button */

.overflow-top #scroll-up {
    display: block;
    top: 0;
}

/* down button */

.overflow-bottom #scroll-down {
    display: block;
    bottom: 0;
}