body {
    background-image: url("../images/background.jpg");
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
    background-attachment: fixed; /* keeps the image fixed while content scrolls */
    min-height: 100vh;
}

.overlay-container {
    width: 90%;
    margin: 0 auto;
    opacity: .85;
    box-shadow: gray 0px 4px 8px 0px;
}

.link {
    text-decoration: none;
}

/* Collapsible mobile nav */
#mobile-nav {
    max-height: 0;
    overflow: hidden;
    opacity: 0;
    transition: max-height 320ms ease, opacity 200ms ease;
    margin-top: 8px;
}

/* When open, allow content height up to large value (animated) */
#mobile-nav.open {
    opacity: 1;
    max-height: 720px; /* enough for several links; will collapse if less */
}

/* Links inside */
#mobile-nav a {
    display: block;
    padding: 12px 16px;
    color: inherit;
    text-decoration: none;
}

#mobile-nav a:first-child { border-top: none; }