website/nav.css

body { margin: 0; }

body > * {
    box-sizing: border-box;
    float: left;
    padding: 4px;
}

#main {
    position: absolute;
    top: 0;
    left: 192px;
    width: calc(100% - 192px);
}

#nav {
    width: 192px;
    height: 100%;
    background-color: #cccccc;
    position: fixed;
    top: 0;
    left: 0;
}

.nav-item {
    padding: 0px 4px 0px 4px;
    margin: 2px;
    background-color: #800000;
    color: #ddd;
    display: block;
}

.nav-item:hover {
    background-color: #ffffff;
    color: #800000;
}

.nav-section-bottom {
    position: absolute;
    bottom: 0;
}

@media only screen and (max-width: 576px) {
    #main, #nav {
        position: initial;
        width: 100%;
    }
    #nav { height: initial; }
    .nav-item { padding: 4px; }
    .nav-section-bottom{ display: hidden; }
}