/* ── CS_basics Sticky Navigation Bar & Controls ── */

.top-bar {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.6rem 1.5rem;
  background: rgba(247, 241, 227, 0.95);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: var(--transition);
}

[data-theme="white"] .top-bar {
  background: rgba(255, 255, 255, 0.95);
}

[data-theme="dark"] .top-bar {
  background: rgba(10, 10, 12, 0.92);
}

.top-bar-brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 700;
  font-size: 0.92rem;
  letter-spacing: -0.02em;
  color: var(--text);
  text-decoration: none;
  flex-shrink: 0;
}

.top-bar-brand:hover {
  color: var(--accent);
}

.top-bar-brand .prompt-sign {
  color: var(--accent);
  font-weight: 800;
}

.top-bar-brand .year-badge {
  font-size: 0.65rem;
  background: var(--surface-active);
  color: var(--accent);
  border: 1px solid var(--accent-border);
  padding: 0.12rem 0.45rem;
  border-radius: var(--radius-sm);
  margin-left: 0.2rem;
  letter-spacing: 0.05em;
  font-weight: 700;
}

.top-bar-nav {
  display: flex;
  align-items: center;
  gap: 0.3rem;
  flex-wrap: nowrap;
}

.top-bar-link {
  color: var(--text-muted);
  font-size: 0.8rem;
  font-weight: 500;
  padding: 0.35rem 0.6rem;
  border-radius: var(--radius-sm);
  transition: var(--transition);
  text-decoration: none;
  white-space: nowrap;
}

.top-bar-link:hover {
  color: var(--text);
  background: var(--surface-hover);
}

.top-bar-link.active {
  color: var(--accent);
  background: var(--accent-dim);
  font-weight: 600;
}

.theme-toggle-btn {
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 0.32rem 0.65rem;
  font-size: 0.78rem;
  border-radius: var(--radius-md);
  margin-left: 0.4rem;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  cursor: pointer;
  transition: var(--transition);
  font-family: var(--font-mono);
  white-space: nowrap;
}

.theme-toggle-btn:hover {
  border-color: var(--text-muted);
  background: var(--surface-hover);
}

.cloud-nav-btn {
  background: var(--surface);
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: 0.32rem 0.65rem;
  font-size: 0.78rem;
  border-radius: var(--radius-md);
  margin-left: 0.3rem;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  cursor: pointer;
  transition: var(--transition);
  font-family: var(--font-mono);
  white-space: nowrap;
}

.cloud-nav-btn:hover {
  border-color: var(--accent);
  color: var(--text);
  background: var(--surface-hover);
}

.cloud-nav-btn.connected {
  background: rgba(22, 163, 74, 0.12);
  border-color: rgba(22, 163, 74, 0.4);
  color: #15803d;
}

[data-theme="dark"] .cloud-nav-btn.connected {
  color: #4ade80;
}

.mobile-menu-btn {
  display: none;
  background: transparent;
  border: none;
  color: var(--text);
  font-size: 1.35rem;
  padding: 0.3rem 0.5rem;
  cursor: pointer;
  border-radius: var(--radius-sm);
}

.mobile-menu-btn:hover {
  background: var(--surface-hover);
}

/* ── Mobile Overlay Navigation ── */
.mobile-nav-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: var(--bg);
  z-index: 999;
  padding: 4.5rem 2rem 2.5rem;
  flex-direction: column;
  gap: 0.5rem;
  overflow-y: auto;
}

.mobile-nav-overlay.open {
  display: flex;
}

.mobile-nav-close {
  position: absolute;
  top: 1.25rem;
  right: 1.5rem;
  background: transparent;
  border: none;
  color: var(--text);
  font-size: 1.5rem;
  cursor: pointer;
  padding: 0.5rem;
}

.mobile-nav-section-title {
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.1em;
  color: var(--text-dim);
  text-transform: uppercase;
  margin-top: 1.25rem;
  margin-bottom: 0.25rem;
  padding-bottom: 0.25rem;
  border-bottom: 1px dashed var(--border);
}

.mobile-nav-section-title:first-of-type {
  margin-top: 0;
}

.mobile-nav-overlay .mobile-nav-link {
  font-size: 1.05rem;
  font-weight: 600;
  padding: 0.55rem 0.25rem;
  border-bottom: 1px solid var(--border-subtle);
  color: var(--text);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: var(--transition);
}

.mobile-nav-overlay .mobile-nav-link:hover {
  color: var(--accent);
  padding-left: 0.5rem;
}

.mobile-nav-overlay .mobile-nav-link.active {
  color: var(--accent);
  font-weight: 700;
}

@media (max-width: 960px) {
  .top-bar-link {
    display: none;
  }
  .mobile-menu-btn {
    display: block;
  }
}