.nav-slider{
    position:fixed;
    top:-100%;
    left:0;
    width:100%;
    height:calc(100% - 60px);
    background-color:$white;
    z-index:1;
    visibility:hidden;
    transition:top 0.2s, visibility 0s;
    -o-transition:top 0.2s, visibility 0s;
    -ms-transition:top 0.2s, visibility 0s;
    -moz-transition:top 0.2s, visibility 0s;
    -webkit-transition:top 0.2s, visibility 0s;
    padding-top:40px;

    &.is_visible{
        top:60px;
        visibility: visible;
    }
}