/* === Theme Variables === */
:root[data-theme="dark"] {
  --bg: #1e1e2e;
  --bg-secondary: #262637;
  --bg-card: #2a2a3d;
  --text: #cdd6f4;
  --text-muted: #9399b2;
  --heading: #f0f0f5;
  --link: #df51a7;
  --link-hover: #f080c0;
  --border: #3a3a52;
  --code-bg: #2a2a3d;
  --sidebar-bg: #181825;
  --sidebar-active: #df51a7;
  --toc-bg: #262637;
  --table-bg: #2a2a3d;
  --table-stripe: #262637;
  --toggle-icon-sun: none;
  --toggle-icon-moon: inline;
}

:root[data-theme="light"] {
  --bg: #ffffff;
  --bg-secondary: #f5f5f7;
  --bg-card: #ffffff;
  --text: #2c2c2e;
  --text-muted: #6e6e73;
  --heading: #1d1d1f;
  --link: #c02080;
  --link-hover: #a01868;
  --border: #d2d2d7;
  --code-bg: #f5f5f7;
  --sidebar-bg: #f5f5f7;
  --sidebar-active: #c02080;
  --toc-bg: #f9f9fb;
  --table-bg: #ffffff;
  --table-stripe: #f9f9fb;
  --toggle-icon-sun: inline;
  --toggle-icon-moon: none;
}

/* === Reset & Base === */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; overflow-x: hidden; }
body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  font-size: 16px;
}

/* === Layout === */
.layout {
  display: flex;
  min-height: 100vh;
}

/* === Sidebar === */
.sidebar {
  width: 240px;
  flex-shrink: 0;
  background: var(--sidebar-bg);
  border-right: 1px solid var(--border);
  padding: 1.5rem 1rem;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
}

.sidebar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.5rem;
}

.site-title {
  font-family: 'Caveat', cursive;
  font-size: 1.4rem;
  font-weight: 600;
  color: var(--heading);
  text-decoration: none;
}

#theme-toggle {
  background: none;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 4px 8px;
  cursor: pointer;
  font-size: 1rem;
  color: var(--text);
}
#theme-toggle:hover { border-color: var(--link); }
.icon-sun { display: var(--toggle-icon-sun); }
.icon-moon { display: var(--toggle-icon-moon); }

.nav-list {
  list-style: none;
}
.nav-list li { margin-bottom: 2px; }
.nav-list a {
  display: block;
  padding: 6px 10px;
  border-radius: 6px;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.15s, background 0.15s;
}
.nav-list a:hover { color: var(--heading); background: var(--bg-secondary); }
.nav-list a.active {
  color: var(--sidebar-active);
  background: var(--bg-secondary);
  font-weight: 600;
}

/* === Main Content === */
.content {
  flex: 1;
  max-width: 52rem;
  margin: 0 auto;
  padding: 2rem 2.5rem;
  min-width: 0;
}

/* === Homepage === */
.content > article > h1 { font-size: 2rem; color: var(--heading); margin-bottom: 0.5rem; }
.content > article > h2 { font-size: 1.3rem; color: var(--heading); margin-top: 1.5rem; margin-bottom: 0.5rem; }
.content > article > p { margin-bottom: 1rem; }
.content > article > ul { padding-left: 1.5rem; margin-bottom: 1rem; }

/* === Course Grid === */
.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1rem;
  margin-top: 1rem;
}
.course-card {
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 1rem 1.2rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 8px;
  text-decoration: none;
  transition: border-color 0.15s, transform 0.1s;
}
.course-card:hover { border-color: var(--link); transform: translateY(-1px); }
.course-code { font-weight: 600; color: var(--heading); font-size: 0.95rem; }
.course-prof { color: var(--text-muted); font-size: 0.85rem; }
.course-words { color: var(--text-muted); font-size: 0.8rem; }

/* === Course Page === */
.course-header { text-align: center; margin-bottom: 1.5rem; }
.course-title { font-size: 1.6rem; color: var(--heading); margin-bottom: 0.3rem; }
.caveat { font-family: 'Caveat', cursive; }
.course-prof { color: var(--text-muted); font-size: 1.1rem; }
.reading-time { color: var(--text-muted); font-size: 0.8rem; font-style: italic; margin-top: 0.5rem; }

/* TOC */
.toc-details {
  background: var(--toc-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.2rem;
  margin-bottom: 1.5rem;
  overflow-x: hidden;
  word-break: break-word;
}
.toc-details summary {
  cursor: pointer;
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--text-muted);
}
.toc-details ul { padding-left: 1.2rem; margin-top: 0.5rem; }
.toc-details li { margin-bottom: 2px; }
.toc-details a { color: var(--link); text-decoration: none; font-size: 0.9rem; }
.toc-details a:hover { text-decoration: underline; }

#TableOfContents ul { list-style: none; padding-left: 0; }
#TableOfContents > ul > li > ul { padding-left: 1.2rem; }
#TableOfContents a { color: var(--link); text-decoration: none; font-size: 0.9rem; }
#TableOfContents a:hover { text-decoration: underline; }
#TableOfContents li { margin-bottom: 3px; }

/* === Content Typography === */
.course-content h1 { font-size: 1.5rem; color: var(--heading); margin: 2.5rem 0 1rem; padding-bottom: 0.3rem; border-bottom: 1px solid var(--border); }
.course-content h2 { font-size: 1.25rem; color: var(--heading); margin: 2rem 0 0.8rem; }
.course-content h3 { font-size: 1.1rem; color: var(--heading); margin: 1.5rem 0 0.6rem; }
.course-content h4 { font-size: 1rem; color: var(--heading); margin: 1.2rem 0 0.5rem; }
.course-content p { margin-bottom: 1rem; }
.course-content ul, .course-content ol { padding-left: 1.5rem; margin-bottom: 1rem; }
.course-content li { margin-bottom: 0.3rem; }
.course-content a { color: var(--link); text-decoration: none; }
.course-content a:hover { text-decoration: underline; color: var(--link-hover); }

/* Images */
.course-content img { max-width: 100%; height: auto; border-radius: 6px; margin: 1rem 0; }

/* Code */
.course-content code {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.88em;
  background: var(--code-bg);
  padding: 2px 5px;
  border-radius: 4px;
}
.course-content pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem;
  overflow-x: auto;
  margin-bottom: 1rem;
}
.course-content pre code { background: none; padding: 0; }

/* Tables */
.course-content table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 1rem;
  font-size: 0.92rem;
  display: block;
  overflow-x: auto;
}
.course-content th, .course-content td {
  border: 1px solid var(--border);
  padding: 8px 12px;
  text-align: left;
}
.course-content th { background: var(--table-bg); font-weight: 600; }
.course-content tr:nth-child(even) { background: var(--table-stripe); }

/* Blockquotes */
.course-content blockquote {
  border-left: 3px solid var(--link);
  padding: 0.5rem 1rem;
  margin: 1rem 0;
  color: var(--text-muted);
  background: var(--toc-bg);
  border-radius: 0 6px 6px 0;
}
.course-content blockquote p { margin-bottom: 0.5rem; }
.course-content blockquote p:last-child { margin-bottom: 0; }

/* Embedded video */
.embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; margin: 1rem 0; }
.embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; border-radius: 8px; }

/* Video placeholder */
.vp { text-align: center; font-style: italic; color: var(--text-muted); margin: 1rem 0; }

/* Back to top */
.back-to-top {
  display: block;
  text-align: center;
  margin: 3rem 0 1rem;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.85rem;
}
.back-to-top:hover { color: var(--link); }

/* Bold/italic */
.course-content strong { color: var(--heading); }

/* Math/course callout blocks — all theme-aware */
.definition, .theorem, .lemma, .corollary, .proposition,
.example, .remark, .proof, .key-box {
  background: var(--toc-bg);
  padding: 0.8rem 1rem;
  margin: 1rem 0;
  border-radius: 0 6px 6px 0;
  border-left: 3px solid var(--border);
  color: var(--text);
}
.definition { border-left-color: var(--link); }
.theorem { border-left-color: #a855f7; }
.lemma { border-left-color: #eab308; }
.corollary { border-left-color: #22c55e; }
.proposition { border-left-color: #f97316; }
.example { border-left-color: #3b82f6; }
.remark { border-left-color: #6b7280; }
.proof { border-left-color: #6b7280; font-style: italic; }
.key-box { border-left-color: #f0a500; }

.definition strong, .theorem strong, .lemma strong, .corollary strong,
.proposition strong, .example strong, .remark strong, .proof strong,
.key-box strong { color: var(--heading); }
.definition ul, .theorem ul, .example ul, .remark ul,
.definition ol, .theorem ol, .example ol, .remark ol { padding-left: 1.5rem; margin: 0.5rem 0; }
.definition li, .theorem li, .example li, .remark li { margin-bottom: 0.2rem; }

/* Horizontal rules */
.course-content hr, hr { border: none; border-top: 1px solid var(--border); margin: 2rem 0; }

/* Sup */
sup { font-size: 0.75em; }

/* KaTeX overrides for display math spacing */
.katex-display { margin: 1rem 0; overflow-x: auto; overflow-y: hidden; }

/* === Sidebar Search === */
.sidebar-search {
  margin-top: 1rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
}
.search-wrapper {
  position: relative;
}
.search-icon {
  position: absolute;
  left: 10px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
  font-size: 0.85rem;
  pointer-events: none;
}
#search-input {
  width: 100%;
  padding: 8px 10px 8px 30px;
  font-size: 0.85rem;
  font-family: inherit;
  background: var(--bg-secondary);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
  outline: none;
}
#search-input:focus { border-color: var(--link); box-shadow: 0 0 0 2px rgba(223, 81, 167, 0.15); }
#search-input::placeholder { color: var(--text-muted); }

/* === Search Overlay === */
.search-overlay {
  position: fixed;
  top: 0;
  left: 240px;
  right: 0;
  bottom: 0;
  background: var(--bg);
  z-index: 100;
  overflow-y: auto;
  padding: 1.5rem 2.5rem;
}
.search-overlay.hidden { display: none; }
.search-overlay-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
  font-weight: 600;
  color: var(--heading);
}
.search-overlay-header button {
  background: none;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 4px 10px;
  cursor: pointer;
  color: var(--text);
  font-size: 1rem;
}
.search-overlay-header button:hover { border-color: var(--link); }

.search-result {
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding: 12px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  margin-bottom: 8px;
  text-decoration: none;
  transition: border-color 0.15s;
}
.search-result:hover { border-color: var(--link); }
.sr-title { font-weight: 600; color: var(--heading); font-size: 0.95rem; }
.sr-meta { color: var(--text-muted); font-size: 0.8rem; }
.sr-snippet { color: var(--text); font-size: 0.85rem; margin-top: 4px; line-height: 1.5; }
.no-results { color: var(--text-muted); font-style: italic; }
.sr-snippet mark {
  background: rgba(223, 81, 167, 0.25);
  color: var(--heading);
  border-radius: 2px;
  padding: 0 2px;
}

/* === Responsive === */
@media (max-width: 768px) {
  .layout { flex-direction: column; }
  .sidebar {
    width: 100%;
    height: auto;
    position: relative;
    border-right: none;
    border-bottom: 1px solid var(--border);
    padding: 1rem;
  }
  .nav-list { display: flex; flex-wrap: wrap; gap: 4px; }
  .nav-list a { padding: 4px 8px; font-size: 0.85rem; }
  .content { padding: 1.5rem 1rem; }
  .course-grid { grid-template-columns: 1fr; }
  .search-overlay { left: 0; padding: 1rem; }
}