.topbar {
  height: var(--header-h);
  flex-shrink: 0;
  display: flex;
  align-items: center;
  gap: var(--s-7);
  padding: 0 var(--s-10);
  background: var(--canvas);
  border-bottom: 1px solid var(--line-3);
}

.tb-collapse {
  display: none; /* only shown when sidebar is collapsed — toggled via JS class on .shell */
  width: 32px; height: 32px;
  align-items: center; justify-content: center;
  color: var(--ink-4);
  border-radius: var(--r-nav);
  flex-shrink: 0;
}
.shell.sidebar-collapsed .tb-collapse { display: flex; }
.tb-collapse:hover { background: var(--canvas-warm); }

.tb-wordmark {
  display: flex; align-items: center; gap: var(--s-4);
  flex-shrink: 0;
  background: none; border: none; cursor: pointer;
  padding: 4px 2px;
}
.tb-wordmark .dot {
  width: 26px; height: 26px;
  border-radius: 50%;
  background: var(--ink-1);
}
.tb-wordmark .name {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 22px;
  color: var(--ink-1);
  letter-spacing: 0.01em;
}

.tb-nav {
  display: flex; align-items: center; gap: var(--s-9);
  height: 100%;
}
.tb-tab {
  position: relative;
  height: 100%;
  display: flex; align-items: center;
  font-weight: 600;
  font-size: var(--text-xl);
  color: var(--ink-4);
  background: none; border: none; cursor: pointer;
  transition: color var(--dur-fast) var(--ease);
}
.tb-tab:hover { color: var(--ink-2); }
.tb-tab.active { color: var(--brand); }
.tb-tab.active::after {
  content: '';
  position: absolute;
  left: 0; right: 0; bottom: 0;
  height: 2px;
  background: var(--brand);
  border-radius: 2px 2px 0 0;
}

.tb-spacer { flex: 1; }

.tb-lang { position: relative; }
.tb-lang-btn {
  display: flex; align-items: center; gap: 6px;
  padding: 7px 12px;
  border-radius: var(--r-pill);
  border: 1px solid var(--line-1);
  background: var(--canvas);
  color: var(--ink-3);
  font-weight: 600;
  font-size: var(--text-base);
  cursor: pointer;
}
.tb-lang-btn:hover { border-color: var(--brand); color: var(--brand); }
.tb-lang-btn .globe { font-size: 13px; }
.tb-lang-btn .caret { font-size: 9px; color: var(--ink-ghost); }

.tb-lang-menu {
  position: absolute;
  top: calc(100% + 6px); right: 0;
  background: var(--canvas);
  border: 1px solid var(--line-3);
  border-radius: var(--r-card);
  box-shadow: var(--shadow-pop);
  min-width: 160px;
  padding: 4px;
  z-index: 50;
}
.tb-lang-item {
  display: flex; align-items: center; gap: 10px;
  width: 100%;
  padding: 8px 10px;
  border-radius: 7px;
  background: none; border: none;
  text-align: left;
  cursor: pointer;
  font-size: var(--text-base);
  color: var(--ink-3);
}
.tb-lang-item:hover { background: var(--canvas-warm); }
.tb-lang-item.active { color: var(--brand); font-weight: 600; }
.tb-lang-item .code {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--ink-ghost);
  width: 24px;
}
.tb-lang-item.active .code { color: var(--brand); }

@media (max-width: 700px) {
  .topbar { padding: 0 var(--s-7); gap: var(--s-5); }
  .tb-nav { gap: var(--s-7); }
  .tb-tab { font-size: var(--text-lg); }
}