/* Sticky nav */
.main-nav.is-sticky {
    position: fixed;
    top: 0; left: 50%;
    transform: translateX(-50%);
    width: 100%;
    max-width: 1200px;
    z-index: 500;
    box-shadow: 0 3px 14px rgba(0,0,0,.3);
    animation: slideDown .25s ease;
}
@keyframes slideDown {
    from { transform: translateX(-50%) translateY(-100%); opacity: 0; }
    to   { transform: translateX(-50%) translateY(0);    opacity: 1; }
}