$base-duration: 500ms;

.nav {
    position: fixed;
    top: 0;
    left: 0;
    width: 300px;
    height: 100vh;
    margin: 0;
    padding: 0;
    background-color: #444;
    transition: left 500ms ease;
    z-index: 0;
}
.nav ul {
    position: relative;
    padding: 0;
    width: 100%;
    list-style-image: url(../themes/demo5/assets/images/footer-link-arrow.png);
}
.nav ul li {
    position: relative;
    display: block;
}
.nav ul li a {
    position: relative;
    display: block;
    margin: 0;
    padding: 2px 20px;
    color: #444;
    font-size: 12px;
    text-decoration: none;
    font-family: "Roboto", sans-serif;
}
.nav ul li a:before {
    position: absolute;
    content: '';
    top: 0;
    left: 0;
    width: 0;
    height: 100%;
    transition: width 250ms ease;
    z-index: -1;
}
.nav ul li a:hover {
    color: #444;
}
.nav ul li a:hover:before {
    width: 100%;
    height: 100%;
    background-color: #f9eba2;
    transition: width 250ms ease;
}