*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root,
[data-theme="dark"] {
  --bg: #0f1117;
  --sidebar-bg: #161b22;
  --surface: #1c2128;
  --border: #30363d;
  --text: #e6edf3;
  --text-muted: #8b949e;
  --accent: #58a6ff;
  --accent-soft: rgba(88, 166, 255, 0.12);
  --hover: rgba(255, 255, 255, 0.06);
  --active: rgba(88, 166, 255, 0.18);
  --content-bg: #0d1117;
  --sidebar-width: 300px;
  --topbar-height: 56px;
  --radius: 8px;
}

[data-theme="light"] {
  --bg: #ffffff;
  --sidebar-bg: #f6f8fa;
  --surface: #ffffff;
  --border: #d0d7de;
  --text: #1f2328;
  --text-muted: #656d76;
  --accent: #0969da;
  --accent-soft: rgba(9, 105, 218, 0.1);
  --hover: rgba(0, 0, 0, 0.04);
  --active: rgba(9, 105, 218, 0.12);
  --content-bg: #ffffff;
}

html, body {
  height: 100%;
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  overflow: hidden;
}

.app {
  display: flex;
  height: 100vh;
}

/* Sidebar */
.sidebar {
  width: var(--sidebar-width);
  min-width: var(--sidebar-width);
  background: var(--sidebar-bg);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  z-index: 100;
}

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 1rem 0.75rem;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  color: var(--text);
  font-weight: 700;
  font-size: 0.95rem;
}

.logo-icon {
  font-size: 1.1rem;
}

.sidebar-close {
  display: none;
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 1.1rem;
  cursor: pointer;
  padding: 0.25rem;
}

.search-box {
  padding: 0 1rem 0.75rem;
}

.search-box input {
  width: 100%;
  padding: 0.5rem 0.75rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-size: 0.85rem;
  outline: none;
  transition: border-color 0.15s;
}

.search-box input:focus {
  border-color: var(--accent);
}

.search-box input::placeholder {
  color: var(--text-muted);
}

.nav {
  flex: 1;
  overflow-y: auto;
  padding: 0 0.5rem 1rem;
}

.nav-section {
  margin-bottom: 0.25rem;
}

.nav-section-label {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
  padding: 0.75rem 0.75rem 0.35rem;
}

.nav-item {
  display: block;
  width: 100%;
  text-align: left;
  padding: 0.45rem 0.75rem;
  border: none;
  background: none;
  color: var(--text-muted);
  font-size: 0.875rem;
  font-family: inherit;
  border-radius: var(--radius);
  cursor: pointer;
  transition: background 0.12s, color 0.12s;
  text-decoration: none;
}

.nav-item:hover {
  background: var(--hover);
  color: var(--text);
}

.nav-item.active {
  background: var(--active);
  color: var(--accent);
  font-weight: 500;
}

.nav-item.indent-1 { padding-left: 1.5rem; }
.nav-item.indent-2 { padding-left: 2.25rem; font-size: 0.82rem; }

.nav-item.hidden {
  display: none;
}

.sidebar-footer {
  padding: 0.75rem 1rem;
  border-top: 1px solid var(--border);
  font-size: 0.75rem;
  color: var(--text-muted);
}

.sidebar-footer a {
  color: var(--accent);
  text-decoration: none;
}

.sidebar-footer a:hover {
  text-decoration: underline;
}

/* Main content */
.main {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.topbar {
  height: var(--topbar-height);
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0 1.25rem;
  border-bottom: 1px solid var(--border);
  background: var(--sidebar-bg);
}

.menu-btn {
  display: none;
  background: none;
  border: none;
  color: var(--text);
  cursor: pointer;
  padding: 0.35rem;
  border-radius: var(--radius);
}

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

.page-heading {
  flex: 1;
  font-size: 1rem;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.open-tab {
  color: var(--text-muted);
  padding: 0.35rem;
  border-radius: var(--radius);
  transition: color 0.12s, background 0.12s;
}

.open-tab:hover {
  color: var(--accent);
  background: var(--hover);
}

.theme-toggle {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  padding: 0.35rem;
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  transition: color 0.12s, background 0.12s;
}

.theme-toggle:hover {
  color: var(--accent);
  background: var(--hover);
}

.theme-toggle .icon-sun,
.theme-toggle .icon-moon {
  display: none;
}

[data-theme="dark"] .theme-toggle .icon-sun { display: block; }
[data-theme="light"] .theme-toggle .icon-moon { display: block; }

.content {
  flex: 1;
  position: relative;
  background: var(--content-bg);
}

#viewer {
  width: 100%;
  height: 100%;
  border: none;
  display: block;
}

.overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: 90;
}

/* Mobile */
@media (max-width: 768px) {
  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    height: 100%;
    transform: translateX(-100%);
    transition: transform 0.25s ease;
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .sidebar-close {
    display: block;
  }

  .menu-btn {
    display: flex;
  }

  .overlay.visible {
    display: block;
  }
}

/* Scrollbar */
.nav::-webkit-scrollbar {
  width: 6px;
}

.nav::-webkit-scrollbar-track {
  background: transparent;
}

.nav::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 3px;
}