@media (max-width: 768px) {
    :root { --sidebar-w: 100%; }

    #app { position: relative; }

    #sidebar {
        position: absolute;
        inset: 0;
        width: 100%;
        z-index: 30;
        transform: translateX(0);
        transition: transform var(--transition);
    }
    #sidebar.hidden { transform: translateX(-100%); }

    #chat-area {
        position: absolute;
        inset: 0;
        transform: translateX(100%);
        transition: transform var(--transition);
        z-index: 25;
    }
    #chat-area.show { transform: translateX(0); }

    /* Back button in chat header on mobile */
    #btn-back-mobile {
        display: flex !important;
        width: 36px; height: 36px;
        border-radius: 50%;
        align-items: center; justify-content: center;
        color: rgba(255,255,255,.85);
        font-size: 22px;
    }

    .bubble { max-width: 85%; }

    #message-list { padding: 10px 3%; }

    /* Keyboard avoiding — use dvh */
    #chat-window { height: 100dvh; }

    /* Larger tap targets */
    .input-btn, #btn-send { width: 46px; height: 46px; }
    .msg-action-btn { width: 32px; height: 32px; font-size: 16px; }
}

@media (min-width: 769px) {
    #btn-back-mobile { display: none !important; }
}

/* PWA standalone mode */
@media (display-mode: standalone) {
    #app { height: 100dvh; }
    /* account for iPhone notch */
    .sidebar-header, #chat-header {
        padding-top: max(12px, env(safe-area-inset-top));
    }
}

/* Touch — no hover effects on touch devices */
@media (hover: none) {
    .msg-actions { display: none !important; }
    .bubble { -webkit-user-select: none; user-select: none; }
}