@media (max-width: 680px) {
    .home-feed-page .home-topbar,
    .home-feed-page .feed-header,
    .home-feed-page .mobile-bottom-nav {
        transition: transform 180ms ease-out;
    }
    .home-feed-page .feed-header { top: var(--feed-topbar-height, 64px); }
    /* Preserve the document geometry: hiding chrome must not move the feed. */
    .home-feed-page.feed-chrome-hidden .home-topbar,
    .home-feed-page.feed-chrome-hidden .feed-header {
        transform: translateY(calc(-1 * var(--feed-chrome-height, 128px)));
        pointer-events: none;
    }
    .home-feed-page.feed-chrome-hidden .mobile-bottom-nav {
        transform: translateY(calc(100% + 32px + env(safe-area-inset-bottom)));
        pointer-events: none;
    }
}
@media (max-width: 680px) and (prefers-reduced-motion: reduce) {
    .home-feed-page .home-topbar,
    .home-feed-page .feed-header,
    .home-feed-page .mobile-bottom-nav { transition: none; }
}