/* App shell: sidebar (drawer on mobile) + main column with topbar, chat scroll, composer. */
.app { display: flex; height: 100dvh; overflow: hidden; }

/* ---------- sidebar ---------- */
.sidebar {
  width: var(--sidebar-w); flex-shrink: 0; display: flex; flex-direction: column;
  background: var(--bg-soft); border-right: 1px solid var(--border);
  transition: margin-left .22s var(--ease), transform .22s var(--ease);
}
.app.sidebar-collapsed .sidebar { margin-left: calc(-1 * var(--sidebar-w)); }
.sidebar-head { display: flex; align-items: center; gap: 10px; height: var(--topbar-h); padding: 0 10px 0 14px; }
.brand { display: flex; align-items: center; gap: 10px; flex: 1; min-width: 0; text-decoration: none; color: var(--text); }
.brand img { width: 28px; height: 28px; border-radius: 8px; object-fit: contain; }
.brand-name { font-weight: 700; font-size: 15px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.sidebar-new { margin: 4px 10px 10px; width: calc(100% - 20px); justify-content: flex-start; border-radius: var(--radius); }
.history-list { flex: 1; overflow-y: auto; padding: 0 8px 8px; }
.sidebar-foot { border-top: 1px solid var(--border); padding: 10px; }
.sidebar-backdrop { display: none; }

/* ---------- main ---------- */
.main { flex: 1; min-width: 0; display: flex; flex-direction: column; position: relative; }
.topbar {
  height: var(--topbar-h); flex-shrink: 0; display: flex; align-items: center; gap: 6px;
  padding: 0 10px; border-bottom: 1px solid transparent; background: var(--bg);
}
.topbar.scrolled { border-bottom-color: var(--border); }
.topbar-title { font-weight: 700; font-size: 15px; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; min-width: 0; }
.topbar-spacer { flex: 1; }
.device-slot { display: flex; align-items: center; gap: 6px; min-width: 0; }
.app:not(.sidebar-collapsed) .only-collapsed { display: none; }

.chat-scroll { flex: 1; overflow-y: auto; overflow-x: hidden; overscroll-behavior: contain; }
.chat-column { max-width: var(--chat-max); margin: 0 auto; padding: 8px 20px 24px; }

.composer-wrap { flex-shrink: 0; background: var(--bg); padding: 0 16px calc(10px + env(safe-area-inset-bottom)); }
.composer-wrap > * { max-width: var(--chat-max); margin-left: auto; margin-right: auto; }
.composer-note { text-align: center; font-size: 12px; color: var(--text-3); margin-top: 6px; }

/* ---------- empty state ---------- */
.empty-state { min-height: 100%; display: flex; flex-direction: column; align-items: center; justify-content: center; padding: 24px 0 8px; text-align: center; }
.empty-logo { width: 44px; height: 44px; border-radius: 13px; object-fit: contain; margin-bottom: 10px; }
.empty-state h1 { margin: 0 0 6px; font-size: 22px; font-weight: 800; letter-spacing: -0.01em; }
.empty-state p { margin: 0 0 16px; color: var(--text-2); max-width: 520px; }
/* feature cards: styles live in chat.css (.feat-*) */
.empty-state .feat-grid { width: 100%; }
.empty-state .fc-safe-all { align-self: flex-start; }

/* ---------- mobile ---------- */
@media (max-width: 768px) {
  .sidebar {
    position: fixed; inset: 0 auto 0 0; z-index: 50; width: min(86vw, 320px);
    transform: translateX(-100%); box-shadow: var(--shadow-lg); margin-left: 0 !important;
  }
  .app.sidebar-open .sidebar { transform: none; }
  .sidebar-backdrop { display: block; position: fixed; inset: 0; z-index: 40; background: var(--overlay); opacity: 0; pointer-events: none; transition: opacity .2s; }
  .app.sidebar-open .sidebar-backdrop { opacity: 1; pointer-events: auto; }
  .app .only-collapsed { display: inline-flex !important; }
  .only-desktop { display: none !important; }
  .chat-column { padding: 8px 14px 20px; }
  .composer-wrap { padding: 0 10px calc(8px + env(safe-area-inset-bottom)); }
  .topbar-title { font-size: 14px; }
  .empty-state h1 { font-size: 21px; }
}
@media (min-width: 769px) { .only-mobile { display: none !important; } }