/* ============================================================================
   Tennis Unified — taichinow-inspired redesign
   Light theme with green accents, DM Sans typography, modern card layouts
   ============================================================================ */

:root {
  --bg: #f8faf9;
  --card: #ffffff;
  --card-hover: #f9fafb;
  --ink: #1c1917;
  --ink-muted: #44403c;
  --muted: #78716c;
  --accent: #059669;
  --accent-dark: #047857;
  --accent-light: #d1fae5;
  --border: #e7e5e4;
  --shadow: 0 1px 3px rgba(0, 0, 0, .06), 0 1px 2px rgba(0, 0, 0, .04);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, .08);
  --shadow-lg: 0 10px 25px rgba(0, 0, 0, .12);
  --radius: 12px;
  --radius-sm: 6px;
  --header-bg: linear-gradient(135deg, #064e3b 0%, #059669 50%, #10b981 100%);
  --code-bg: #f3f4f6;
  --toc-bg: #f3f4f6;
}

/* === Dark theme override ============================================== */

[data-theme="dark"] {
  --bg: #0f1714;
  --card: #1a2421;
  --card-hover: #223029;
  --ink: #e7e5e4;
  --ink-muted: #a8a29e;
  --muted: #8a8580;
  --accent: #34d399;
  --accent-dark: #6ee7b7;
  --accent-light: #064e3b;
  --border: #2d3a35;
  --shadow: 0 1px 3px rgba(0, 0, 0, .3), 0 1px 2px rgba(0, 0, 0, .2);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, .35);
  --shadow-lg: 0 10px 25px rgba(0, 0, 0, .45);
  --code-bg: #1a2421;
  --toc-bg: #1a2421;
  color-scheme: dark;
}

[data-theme="dark"] body { background: var(--bg); color: var(--ink); }
[data-theme="dark"] h1,
[data-theme="dark"] h2,
[data-theme="dark"] h3,
[data-theme="dark"] h4 { color: var(--accent-dark); }
[data-theme="dark"] .tu-card { background: var(--card); border-color: var(--border); }
[data-theme="dark"] .tu-card:hover { background: var(--card-hover); }
[data-theme="dark"] a { color: var(--accent-dark); }
[data-theme="dark"] a:hover { color: var(--accent); }
[data-theme="dark"] code,
[data-theme="dark"] pre { background: var(--code-bg); color: var(--ink); }
[data-theme="dark"] hr { border-color: var(--border); }
[data-theme="dark"] blockquote { background: var(--card); border-left-color: var(--accent); color: var(--ink-muted); }
[data-theme="dark"] .tu-topnav { background: var(--card); border-bottom-color: var(--border); }
[data-theme="dark"] .tu-breadcrumb { color: var(--muted); }
[data-theme="dark"] .tu-breadcrumb__current { color: var(--ink); }
[data-theme="dark"] table { color: var(--ink); }
[data-theme="dark"] th,
[data-theme="dark"] td { border-color: var(--border); }
[data-theme="dark"] img { opacity: 0.92; }
[data-theme="dark"] .md-typeset pre { background: var(--code-bg); }
[data-theme="dark"] .md-typeset code { background: var(--code-bg); color: var(--ink); }

/* Material theme palette overrides for dark */
[data-theme="dark"] [data-md-color-scheme="slate"] {
  --md-default-bg-color: var(--bg);
  --md-default-fg-color: var(--ink);
  --md-default-fg-color--light: var(--ink-muted);
  --md-default-fg-color--lighter: var(--muted);
  --md-typeset-a-color: var(--accent-dark);
  --md-primary-fg-color: var(--ink);
  --md-primary-bg-color: var(--bg);
  --md-accent-fg-color: var(--accent);
}

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

html {
  scroll-behavior: smooth;
  font-size: 25px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.65;
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* === Headings ============================================================ */

h1, h2, h3, h4, h5, h6 {
  margin-top: 1.5em;
  margin-bottom: 0.6em;
  font-weight: 600;
  line-height: 1.3;
  color: var(--ink);
}

h1 { font-size: 2.2rem; letter-spacing: -0.02em; }
h2 { font-size: 1.7rem; color: var(--accent-dark); padding-bottom: 0.4em; border-bottom: 2px solid var(--accent-light); }
h3 { font-size: 1.3rem; color: var(--accent-dark); }
h4 { font-size: 1.1rem; color: var(--ink-muted); }
h5 { font-size: 1rem; }
h6 { font-size: 0.9rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.04em; }

p { margin: 0.8em 0; }
ul, ol { padding-left: 1.5em; margin: 0.6em 0; }
li { margin: 0.2em 0; }

/* === Markdown / Article content font sizes (mobile-friendly) =============== */

.md-content p,
.markdown-body p,
.article-body p {
  font-size: 1.0625rem; /* 17px at base 16px */
  line-height: 1.7;
}

.md-content h1,
.markdown-body h1,
.article-body h1 { font-size: 2.4rem; margin-top: 1.8em; }
.md-content h2,
.markdown-body h2,
.article-body h2 { font-size: 1.9rem; margin-top: 1.6em; }
.md-content h3,
.markdown-body h3,
.article-body h3 { font-size: 1.5rem; margin-top: 1.4em; }
.md-content h4,
.markdown-body h4,
.article-body h4 { font-size: 1.2rem; margin-top: 1.3em; }
.md-content h5,
.markdown-body h5,
.article-body h5 { font-size: 1.05rem; margin-top: 1.2em; }
.md-content h6,
.markdown-body h6,
.article-body h6 { font-size: 0.9rem; margin-top: 1.1em; }

.md-content li,
.markdown-body li,
.article-body li {
  margin-bottom: 0.35em;
}

.md-content table,
.markdown-body table { font-size: 0.95rem; max-width: 100%; table-layout: fixed; word-wrap: break-word; }
.md-content table th, .md-content table td,
.markdown-body table th, .markdown-body table td { word-wrap: break-word; overflow-wrap: break-word; }
.md-content code,
.markdown-body code,
.article-body code { font-size: 0.9rem; }

a {
  color: var(--accent-dark);
  text-decoration: none;
  transition: color 0.15s ease;
}
a:hover { color: var(--accent); text-decoration: underline; }

code {
  background: var(--code-bg);
  padding: 0.15em 0.35em;
  border-radius: 4px;
  font-family: 'SF Mono', Consolas, monospace;
  font-size: 0.9em;
}

pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 1em;
  overflow-x: auto;
  font-size: 0.9em;
  line-height: 1.5;
  max-width: 100%;
}

blockquote {
  border-left: 4px solid var(--accent);
  padding: 0.5em 1em;
  background: var(--card);
  color: var(--ink-muted);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  margin: 1em 0;
}

img { max-width: 100%; height: auto; border-radius: var(--radius-sm); }

hr {
  border: 0;
  border-top: 1px solid var(--border);
  margin: 2em 0;
}

table { width: 100%; border-collapse: collapse; margin: 1.5em 0; }
table th, table td { padding: 0.75em 1em; border: 1px solid var(--border); text-align: left; }
table th { background: var(--card); font-weight: 600; }
table tr:nth-child(even) td { background: rgba(0, 0, 0, 0.02); }

/* === Breadcrumb (top of chapter pages) ============================= */

.tu-breadcrumb {
  max-width: 900px;
  margin: 1rem auto 0.5rem;
  padding: 0.5rem 1.5rem;
  font-size: 0.9rem;
  color: var(--muted);
}

.tu-breadcrumb__list {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.25rem 0.5rem;
  margin: 0;
  padding: 0;
  align-items: center;
}
.tu-breadcrumb__item { margin: 0; }
.tu-breadcrumb__link {
  color: var(--accent-dark);
  text-decoration: none;
}
.tu-breadcrumb__link:hover { text-decoration: underline; }
.tu-breadcrumb__sep { color: var(--muted); margin: 0 0.15rem; user-select: none; }
.tu-breadcrumb__current { color: var(--ink); font-weight: 500; }

/* === Chapter nav (Prev / Home / Next) ============================== */

.tu-chapter-nav {
  max-width: 900px;
  margin: 2.5rem auto 3rem;
  padding: 0 1.5rem;
  border-top: 1px solid var(--border);
}
.tu-chapter-nav__inner {
  display: flex;
  justify-content: space-between;
  align-items: stretch;
  gap: 0.75rem;
  padding-top: 1.5rem;
  flex-wrap: wrap;
}
.tu-chapter-nav__link {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
  padding: 0.85rem 1.15rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--card);
  text-decoration: none;
  color: var(--accent-dark);
  min-width: 0;
  flex: 1 1 30%;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}
.tu-chapter-nav__link:hover {
  border-color: var(--accent);
  box-shadow: var(--shadow);
  text-decoration: none;
}
.tu-chapter-nav__link--prev { text-align: left; }
.tu-chapter-nav__link--home { text-align: center; align-self: center; flex: 0 1 auto; }
.tu-chapter-nav__link--next { text-align: right; }
.tu-chapter-nav__link--disabled {
  color: var(--muted);
  border-color: var(--border);
  background: var(--bg);
  cursor: not-allowed;
  pointer-events: none;
}
.tu-chapter-nav__direction {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--accent-dark);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.tu-chapter-nav__title {
  font-size: 0.98rem;
  font-weight: 500;
  color: var(--ink);
}
@media (max-width: 600px) {
  .tu-chapter-nav__inner { flex-direction: column; }
  .tu-chapter-nav__link { text-align: left !important; }
  .tu-chapter-nav__link--home { text-align: center !important; }
}

/* === Cards (for sections grid) ========================================= */

.tu-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: var(--shadow);
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
  display: flex;
  flex-direction: column;
  color: inherit;
}
.tu-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-light);
}
.tu-card h3:first-child { margin-top: 0; color: var(--accent-dark); }

/* === Grid layout ======================================================== */

.tu-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 380px));
  gap: 20px;
  margin-bottom: 32px;
  max-width: 100%;
  justify-content: start;
}

.tu-card {
  max-width: 380px;
  width: 100%;
  box-sizing: border-box;
}
@media (max-width: 768px) {
  .tu-grid { grid-template-columns: 1fr; }
}

/* === Buttons ============================================================ */

.btn, .tu-btn {
  display: inline-block;
  font-weight: 600;
  font-size: 0.9rem;
  line-height: 1.5;
  padding: 0.5rem 1.1rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  transition: all 0.15s ease;
  border: 1px solid transparent;
  cursor: pointer;
}
.btn-primary, .tu-btn-primary {
  background: var(--accent);
  color: #fff !important;
  border-color: var(--accent);
}
.btn-primary:hover, .tu-btn-primary:hover {
  background: var(--accent-dark);
  border-color: var(--accent-dark);
  color: #fff !important;
  text-decoration: none;
}
.btn-outline, .tu-btn-outline {
  background: var(--card);
  color: var(--accent-dark);
  border-color: var(--accent);
}
.btn-outline:hover, .tu-btn-outline:hover {
  background: var(--accent-light);
  text-decoration: none;
}



/* === Material MkDocs Chrome Removal ======================================= */
.md-logo { display: none !important; }
.md-skip { display: none !important; }
.md-clipboard { display: none !important; }

/* === Top navigation (taichinow-style flattened) ========================== */

.tu-topnav {
  display: flex;
  justify-content: center;
  gap: 1.5rem;
  background: var(--card);
  border-bottom: 1px solid var(--border);
  padding: 0.5rem;
  position: sticky;
  top: 0;
  z-index: 99;
  box-shadow: var(--shadow);
}

.tu-nav-item {
  display: flex;
  align-items: center;
  justify-content: center;
  text-decoration: none;
  font-size: 1.4rem;
  width: 2rem;
  height: 2rem;
  border-radius: 50%;
  transition: transform 0.2s ease, background 0.2s ease;
  color: var(--muted);
}

.tu-nav-item:hover, .tu-nav-item:focus {
  transform: scale(1.15);
  background: var(--accent-light);
  color: var(--accent-dark);
}

.tu-nav-item.active {
  color: var(--accent);
  background: var(--accent-light);
}

.tu-nav-darkmode {
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  width: 2rem;
  height: 2rem;
  border-radius: 50%;
  transition: transform 0.2s ease, background 0.2s ease;
  color: var(--muted);
}

.tu-nav-darkmode:hover {
  background: var(--accent-light);
  color: var(--accent-dark);
}

.tu-nav-darkmode.active {
  color: var(--accent);
  background: var(--accent-light);
}

/* Hide old dropdown navbar */
.tu-navbar { display: none !important; }

/* Emoji + text label inside nav item */
.tu-nav-item .tu-nav-emoji {
  display: inline-block;
  font-size: 1.4rem;
  line-height: 1;
}

.tu-nav-item .tu-nav-text {
  display: inline-block;
  font-size: 0.85rem;
  font-weight: 500;
  margin-left: 0.35rem;
  white-space: nowrap;
}

.tu-nav-item:hover .tu-nav-text {
  color: var(--accent-dark);
}

/* Adjust nav-item layout to support emoji + text */
.tu-topnav {
  gap: 1.2rem;
  flex-wrap: wrap;
  justify-content: center;
}

.tu-nav-item {
  width: auto;
  height: auto;
  padding: 0.4rem 0.7rem;
  border-radius: 999px;
  gap: 0.25rem;
}

.tu-nav-lang {
  background: var(--accent-light, #d1fae5);
  color: var(--accent-dark, #047857) !important;
  font-weight: 600;
  border: 1px solid var(--accent, #10b981);
  cursor: pointer;
}
.tu-nav-lang:hover {
  background: var(--accent, #10b981);
  color: #ffffff !important;
  transform: scale(1.05);
}




/* === Book Page Styling (margin + border + padding like reading a book) === */

.md-content__inner,
article.md-content__inner,
.article-body,
.markdown-body {
  max-width: 1520px !important;
  margin: 2.5rem auto 3rem !important;
  padding: 2.5rem 4rem 3.5rem !important;
  overflow-x: hidden;
  background: var(--card);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-right: 3px solid var(--accent-light);
  border-radius: var(--radius-sm);
  box-shadow: 0 1px 4px rgba(0,0,0,0.04), 0 8px 24px rgba(0,0,0,0.06);
  position: relative;
}

/* Subtle vertical line decorations on the sides like a book margin */
.md-content__inner::before,
article.md-content__inner::before {
  content: "";
  position: absolute;
  left: 8px;
  top: 1.5rem;
  bottom: 1.5rem;
  width: 1px;
  background: linear-gradient(to bottom, transparent, var(--accent-light) 15%, var(--accent-light) 85%, transparent);
  opacity: 0.5;
}

.md-content__inner::after,
article.md-content__inner::after {
  content: "";
  position: absolute;
  right: 8px;
  top: 1.5rem;
  bottom: 1.5rem;
  width: 1px;
  background: linear-gradient(to bottom, transparent, var(--accent-light) 15%, var(--accent-light) 85%, transparent);
  opacity: 0.5;
}

@media (max-width: 768px) {
  .md-content__inner,
  article.md-content__inner,
  .article-body,
  .markdown-body {
    margin: 1rem 0.5rem 2rem !important;
    padding: 1.5rem 1.25rem 2rem !important;
    border-left-width: 2px;
    border-right-width: 2px;
  }
  
  .md-content__inner::before,
  .md-content__inner::after,
  article.md-content__inner::before,
  article.md-content__inner::after {
    display: none;
  }
}
/* === Footer ============================================================= */

.tu-footer {
  background: var(--card);
  border-top: 1px solid var(--border);
  color: var(--ink-muted);
  padding: 1.5rem 1rem;
  text-align: center;
  font-size: 0.92rem;
  margin-top: 3rem;
}
.tu-footer a { color: var(--accent-dark); }

/* === Layout containers ================================================ */

.tu-container {
  max-width: 1200px;
  margin-left: auto;
  margin-right: auto;
  padding-left: 1rem;
  padding-right: 1rem;
}

main.tu-main {
  padding: 1.5rem 0 3rem;
  min-height: calc(100vh - 56px - 60px);
  flex: 1;
}

/* === Stats / metric cards =========================================== */

.tu-stats {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 14px;
  margin: 1.5rem 0 2rem;
}
.tu-stat-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px 16px;
  text-align: center;
  box-shadow: var(--shadow);
}
.tu-stat-card .num {
  font-size: 2rem;
  font-weight: 700;
  color: var(--accent-dark);
  line-height: 1.2;
}
.tu-stat-card .label {
  font-size: 0.85rem;
  color: var(--muted);
  margin-top: 0.25rem;
}

/* === Search bar (for filterable indexes) ============================ */

.tu-search {
  display: flex;
  margin-bottom: 1.5rem;
}
.tu-search input[type="search"], .tu-search input[type="text"] {
  width: 100%;
  padding: 0.65rem 1rem;
  font-size: 0.95rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--card);
  color: var(--ink);
  font-family: inherit;
}
.tu-search input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-light);
}

/* === Section title (used for category dividers) ====================== */

.tu-section-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--ink);
  margin: 2rem 0 1rem;
  padding-bottom: 0.4em;
  border-bottom: 2px solid var(--accent-light);
}

/* === Hide Material theme chrome ======================================= */

.md-header, .md-header__inner, .md-tabs, .md-tabs__list, .md-header__button,
.md-logo, .md-sidebar, .md-sidebar--primary, .md-sidebar--secondary,
.md-search, .md-footer, .md-header__topic,
[data-md-component="header"], [data-md-component="tabs"],
[data-md-component="sidebar"], [data-md-component="footer"],
header.md-header, nav.md-tabs, .md-skip, a.md-skip,
.md-clipboard, .md-icon, .md-source, .md-banner, .md-dialog,
.md-header__option, .md-version, .md-tabs__link, .md-tabs__item,
.md-footer-meta, .md-footer__inner.md-grid,
.md-copyright, .md-copyright__highlight,
.md-nav--secondary, .md-toc, nav.md-nav--secondary, .toc-card,
.md-path, nav.md-path, .md-path__list, .md-path__item, .md-path__link,
.md-toggle, label[for="__drawer"], label[for="__search"],
label[for="__toc"], label.md-overlay, label.md-header__button,
label.md-nav__title, label.md-nav__link,
label.md-icon, a.md-icon, button.md-icon {
  display: none !important;
}

/* === Defensive: hide any a11y/font-size gadget UI ==================== */

.a11y-gadget, .a11y-toggle, .a11y-panel, .a11y-button,
.a11y-controls, .a11y-fontsize, .a11y-contrast,
[class*="font-size-control"], [class*="font-resize"],
[class*="text-resize"],
button[aria-label*="font size" i], button[aria-label*="text size" i],
button[aria-label*="reset" i] {
  display: none !important;
}

/* === Video player styling =============================================== */

.tp-video-embed {
  margin: 1.5rem 0;
  text-align: center;
}

.tp-video-embed video,
.tp-video-embed iframe,
.video-container {
  position: relative;
  width: 100% !important;
  max-width: 1200px;
  aspect-ratio: 16 / 9;
  height: auto;
  margin: 1.5rem auto;
  overflow: hidden;
  background: #000;
  border-radius: 12px;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.15);
}

.tp-video-embed iframe,
.tp-video-embed video,
.video-container iframe,
.video-container video,
.video-container embed {
  position: absolute !important;
  top: 0 !important;
  left: 0 !important;
  width: 100% !important;
  height: 100% !important;
  border: 0 !important;
  display: block !important;
  object-fit: contain !important;
}

/* Responsive: scale down on small screens */
@media (max-width: 600px) {
  .tp-video-embed video,
  .tp-video-embed iframe,
  .video-container {
    max-width: 100%;
    border-radius: 8px;
  }
}

/* === Responsive ======================================================= */

@media (max-width: 768px) {
  html { font-size: 25px !important; }
  h1 { font-size: 2.2rem; }
  h2 { font-size: 1.7rem; }
  h3 { font-size: 1.4rem; }
  .tu-container { padding-left: 0.75rem; padding-right: 0.75rem; }
  .tu-card, .tu-stat-card { padding: 16px 14px; }
  .tu-navbar__link { font-size: 0.9rem; padding: 10px 10px; }
  .tu-navbar__brand { font-size: 1.1rem; }
  .tu-navbar__lang { font-size: 0.85rem; padding: 0.35rem 0.7rem; }
  .md-content p,
  .markdown-body p,
  .article-body p { font-size: 1rem; }
}

@media (max-width: 480px) {
  html { font-size: 25px !important; }
  body { line-height: 1.75; }
  h1 { font-size: 2rem; }
  h2 { font-size: 1.5rem; }
  h3 { font-size: 1.25rem; }
  .tu-grid { gap: 12px; }
  .tu-card, .tu-stat-card { padding: 14px 12px; }
  .md-content p,
  .markdown-body p,
  .article-body p { font-size: 1rem; }
  .md-content h1,
  .markdown-body h1,
  .article-body h1 { font-size: 1.8rem; }
  .md-content h2,
  .markdown-body h2,
  .article-body h2 { font-size: 1.5rem; }
  .md-content h3,
  .markdown-body h3,
  .article-body h3 { font-size: 1.25rem; }
}

/* === Print ============================================================ */

@media print {
  body { background: #fff; color: #000; }
  .tu-navbar, .tu-footer { display: none; }
  .tu-card { box-shadow: none; border: 1px solid #ccc; }
  a { color: #000; text-decoration: underline; }
}


/* === All Sections Grid (replaces Navigation & Features) ============ */

.tu-section-grid {
  list-style: none;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 360px));
  gap: 1rem;
  padding: 0;
  margin: 1.25rem 0 2rem;
  max-width: 100%;
  justify-content: start;
}

.tu-section-card {
  margin: 0;
  max-width: 360px;
  width: 100%;
  box-sizing: border-box;
}

.tu-section-card {
  margin: 0;
}

.tu-section-card__link {
  display: flex;
  flex-direction: column;
  height: 100%;
  padding: 1.25rem;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  color: inherit;
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
}

.tu-section-card__link:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent);
  text-decoration: none;
}

.tu-section-card__title {
  margin: 0 0 0.4rem;
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--accent-dark);
  line-height: 1.3;
}

.tu-section-card__desc {
  margin: 0;
  font-size: 0.9rem;
  color: var(--ink-muted);
  line-height: 1.5;
  flex: 1;
}

.tu-section-card__cta {
  margin-top: 0.75rem;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent);
}

.tu-section-card__link:hover .tu-section-card__cta {
  color: var(--accent-dark);
}

@media (max-width: 768px) {
  .tu-section-grid {
    grid-template-columns: 1fr;
    gap: 0.75rem;
  }
}


/* === Defensive SVG sizing (prevent oversized icons) ================ */

svg {
  width: 1em !important;
  height: 1em !important;
  max-width: 1.5em !important;
  max-height: 1.5em !important;
  vertical-align: middle;
  fill: currentColor;
}

.md-content svg,
.tu-main svg {
  width: 1em !important;
  height: 1em !important;
  max-width: 1.5em !important;
  max-height: 1.5em !important;
}

.twemoji, span.twemoji, .twemoji svg {
  width: 1em !important;
  height: 1em !important;
  max-width: 1em !important;
  max-height: 1em !important;
  display: inline-block;
  vertical-align: middle;
}

.twemoji.lg, .twemoji.lg svg, span.twemoji.lg {
  width: 1em !important;
  height: 1em !important;
  max-width: 1.2em !important;
  max-height: 1.2em !important;
}

.twemoji.middle, .twemoji.middle svg {
  width: 1em !important;
  height: 1em !important;
  vertical-align: -0.15em;
}


/* === Video players (LARGE SIZE) ===================================== */
/* 16:9 aspect ratio, max 100% width, large responsive height */

.video-container {
  position: relative;
  width: 100%;
  max-width: 1200px;
  aspect-ratio: 16 / 9;
  margin: 1.5rem auto;
  overflow: hidden;
  background: #000;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.video-container iframe,
.video-container video,
.video-container embed {
  position: absolute !important;
  top: 0;
  left: 0;
  width: 100% !important;
  height: 100% !important;
  border: 0;
  display: block;
}

/* Bare iframes outside video-container (fallback) */
.md-content iframe,
.tu-main iframe,
main iframe {
  display: block;
  width: 100% !important;
  max-width: 1200px !important;
  height: auto !important;
  margin: 1.5rem auto !important;
  border: 0;
  border-radius: 12px;
  background: #000;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
  aspect-ratio: 16 / 9;
}

/* Iframes inside video-container: let the container handle aspect ratio */
.video-container iframe,
.video-container video,
.video-container embed {
  aspect-ratio: auto !important;
}

/* YouTube and Vimeo iframes - proportional 16:9 sizing */
iframe[src*="youtube"],
iframe[src*="youtube-nocookie"],
iframe[src*="vimeo"],
iframe.tu-video-iframe {
  display: block !important;
  width: 100% !important;
  max-width: 1200px !important;
  aspect-ratio: 16 / 9 !important;
  height: auto !important;
  margin: 1.5rem auto !important;
  border: 0 !important;
  border-radius: 12px !important;
  background: #000 !important;
}

/* Iframes inside video-container: let the container handle aspect ratio (override above) */
.video-container iframe[src*="youtube"],
.video-container iframe[src*="youtube-nocookie"],
.video-container iframe[src*="vimeo"],
.video-container iframe {
  aspect-ratio: auto !important;
  height: 100% !important;
  position: absolute !important;
  top: 0 !important;
  left: 0 !important;
  margin: 0 !important;
}

@media (max-width: 768px) {
  iframe[src*="youtube"],
  iframe[src*="youtube-nocookie"],
  iframe[src*="vimeo"],
  .video-container,
  .md-content iframe,
  .tu-main iframe,
  main iframe,
  iframe.tu-video-iframe {
    border-radius: 8px !important;
    margin: 1rem auto !important;
  }
}

/* === Books Catalog, Master Book & Notebooks Base Styles === */
.books-filter {
  margin: 1.5rem 0;
  width: 100%;
}

.books-filter-input {
  width: 100%;
  max-width: 600px;
  padding: 0.75rem 1.25rem;
  font-size: 1rem;
  font-family: inherit;
  background: var(--card, #ffffff);
  color: var(--ink, #1c1917);
  border: 1.5px solid var(--border, #e7e5e4);
  border-radius: 8px;
  outline: none;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
  box-sizing: border-box;
}

.books-filter-input:focus {
  border-color: var(--accent, #059669);
  box-shadow: 0 0 0 3px rgba(5, 150, 105, 0.15);
}

.books-filter-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.books-tag-btn {
  background: var(--card, #ffffff);
  border: 1px solid var(--border, #e7e5e4);
  color: var(--ink-muted, #44403c);
  padding: 0.35rem 0.75rem;
  border-radius: 20px;
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.15s ease;
}

.books-tag-btn:hover {
  background: var(--accent-light, #d1fae5);
  color: var(--accent-dark, #047857);
  border-color: var(--accent, #059669);
}

.books-tag-btn.active {
  background: var(--accent, #059669);
  color: #ffffff;
  border-color: var(--accent, #059669);
}

.books-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1.25rem;
  margin: 1.5rem 0 3rem;
  width: 100%;
  box-sizing: border-box;
}

.book-card {
  display: flex;
  flex-direction: column;
  background: var(--card, #ffffff);
  border: 1px solid var(--border, #e7e5e4);
  border-radius: 10px;
  padding: 1.25rem;
  text-decoration: none !important;
  color: inherit !important;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
  box-shadow: var(--shadow, 0 1px 3px rgba(0, 0, 0, 0.06));
  box-sizing: border-box;
}

.book-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md, 0 4px 12px rgba(0, 0, 0, 0.08));
  border-color: var(--accent, #059669);
}

.book-card-domain {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--accent, #059669);
  margin-bottom: 0.4rem;
}

.book-card-title {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--ink, #1c1917);
  line-height: 1.35;
  margin-bottom: 0.4rem;
}

.book-card-author {
  font-size: 0.88rem;
  color: var(--muted, #78716c);
  margin-bottom: 0.85rem;
  flex-grow: 1;
}

.book-card-read {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent-dark, #047857);
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
}

/* Master Book Cards Grid */
.grid.cards > ul {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.25rem;
  list-style: none;
  padding: 0;
  margin: 1.5rem 0;
  width: 100%;
  box-sizing: border-box;
}

.grid.cards > ul > li {
  background: var(--card, #ffffff);
  border: 1px solid var(--border, #e7e5e4);
  border-radius: 10px;
  padding: 1.25rem;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
  box-shadow: var(--shadow, 0 1px 3px rgba(0, 0, 0, 0.06));
  box-sizing: border-box;
}

.grid.cards > ul > li:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md, 0 4px 12px rgba(0, 0, 0, 0.08));
  border-color: var(--accent, #059669);
}

/* PDF Viewer Frame */
iframe.pdf-viewer {
  display: block;
  width: 100% !important;
  max-width: 100% !important;
  height: min(85vh, 1200px) !important;
  min-height: 700px !important;
  border: 1px solid var(--border, #e7e5e4) !important;
  border-radius: 8px !important;
  box-shadow: var(--shadow-md, 0 4px 12px rgba(0, 0, 0, 0.08)) !important;
  background-color: var(--card, #ffffff) !important;
  margin: 1em 0 !important;
  box-sizing: border-box;
}

/* === Dark Mode High-Specificity Overrides === */
[data-theme="dark"],
[data-theme="dark"] body,
body[data-md-color-scheme="slate"] {
  --md-default-bg-color: #0f1714 !important;
  --md-default-fg-color: #e7e5e4 !important;
  --md-default-fg-color--light: #a8a29e !important;
  --md-default-fg-color--lighter: #8a8580 !important;
  --md-typeset-a-color: #4ade80 !important;
  --md-primary-fg-color: #e7e5e4 !important;
  --md-primary-bg-color: #0f1714 !important;
  --md-accent-fg-color: #34d399 !important;
  background-color: #0f1714 !important;
  color: #e7e5e4 !important;
}

[data-theme="dark"] .md-header,
body[data-md-color-scheme="slate"] .md-header {
  background-color: #1a2421 !important;
  color: #e7e5e4 !important;
  border-bottom: 1px solid #2d3a35 !important;
}

[data-theme="dark"] .md-sidebar,
body[data-md-color-scheme="slate"] .md-sidebar {
  background-color: #0f1714 !important;
  color: #e7e5e4 !important;
}

[data-theme="dark"] .md-content,
body[data-md-color-scheme="slate"] .md-content {
  background-color: #0f1714 !important;
}

[data-theme="dark"] .md-content__inner,
[data-theme="dark"] article.md-content__inner,
body[data-md-color-scheme="slate"] .md-content__inner {
  background: #1a2421 !important;
  border-color: #2d3a35 !important;
  color: #e7e5e4 !important;
}

[data-theme="dark"] .tu-topnav,
body[data-md-color-scheme="slate"] .tu-topnav {
  background: #1a2421 !important;
  border-bottom-color: #2d3a35 !important;
}

[data-theme="dark"] .tu-nav-item,
body[data-md-color-scheme="slate"] .tu-nav-item {
  color: #a8a29e !important;
}

[data-theme="dark"] .tu-nav-item:hover,
body[data-md-color-scheme="slate"] .tu-nav-item:hover {
  background: #064e3b !important;
  color: #6ee7b7 !important;
}

[data-theme="dark"] .tu-card,
[data-theme="dark"] .tu-stat-card,
body[data-md-color-scheme="slate"] .tu-card,
body[data-md-color-scheme="slate"] .tu-stat-card {
  background: #1a2421 !important;
  border-color: #2d3a35 !important;
  color: #e7e5e4 !important;
}

[data-theme="dark"] .md-footer,
body[data-md-color-scheme="slate"] .md-footer {
  background-color: #1a2421 !important;
  color: #a8a29e !important;
  border-top: 1px solid #2d3a35 !important;
}

[data-theme="dark"] .tu-footer,
body[data-md-color-scheme="slate"] .tu-footer {
  background: #1a2421 !important;
  border-top: 1px solid #2d3a35 !important;
  color: #a8a29e !important;
}

/* === Books Catalog, Master Book & Notebooks Dark Mode Overrides === */
[data-theme="dark"] .books-filter-input,
body[data-md-color-scheme="slate"] .books-filter-input {
  background: #1a2421 !important;
  border-color: #2d3a35 !important;
  color: #e7e5e4 !important;
}

[data-theme="dark"] .books-filter-input:focus,
body[data-md-color-scheme="slate"] .books-filter-input:focus {
  border-color: #34d399 !important;
  box-shadow: 0 0 0 3px rgba(52, 211, 153, 0.2) !important;
}

[data-theme="dark"] .books-tag-btn,
body[data-md-color-scheme="slate"] .books-tag-btn {
  background: #1a2421 !important;
  border-color: #2d3a35 !important;
  color: #a8a29e !important;
}

[data-theme="dark"] .books-tag-btn:hover,
body[data-md-color-scheme="slate"] .books-tag-btn:hover {
  background: #064e3b !important;
  color: #6ee7b7 !important;
  border-color: #34d399 !important;
}

[data-theme="dark"] .books-tag-btn.active,
body[data-md-color-scheme="slate"] .books-tag-btn.active {
  background: #059669 !important;
  color: #ffffff !important;
  border-color: #059669 !important;
}

[data-theme="dark"] .book-card,
body[data-md-color-scheme="slate"] .book-card {
  background: #1a2421 !important;
  border-color: #2d3a35 !important;
  color: #e7e5e4 !important;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3) !important;
}

[data-theme="dark"] .book-card:hover,
body[data-md-color-scheme="slate"] .book-card:hover {
  background: #223029 !important;
  border-color: #34d399 !important;
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.45) !important;
}

[data-theme="dark"] .book-card-domain,
body[data-md-color-scheme="slate"] .book-card-domain {
  color: #34d399 !important;
}

[data-theme="dark"] .book-card-title,
body[data-md-color-scheme="slate"] .book-card-title {
  color: #e7e5e4 !important;
}

[data-theme="dark"] .book-card-author,
body[data-md-color-scheme="slate"] .book-card-author {
  color: #a8a29e !important;
}

[data-theme="dark"] .book-card-read,
body[data-md-color-scheme="slate"] .book-card-read {
  color: #6ee7b7 !important;
}

[data-theme="dark"] .grid.cards > ul > li,
body[data-md-color-scheme="slate"] .grid.cards > ul > li {
  background: #1a2421 !important;
  border-color: #2d3a35 !important;
  color: #e7e5e4 !important;
  box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3) !important;
}

[data-theme="dark"] .grid.cards > ul > li:hover,
body[data-md-color-scheme="slate"] .grid.cards > ul > li:hover {
  background: #223029 !important;
  border-color: #34d399 !important;
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.45) !important;
}

[data-theme="dark"] .grid.cards > ul > li hr,
body[data-md-color-scheme="slate"] .grid.cards > ul > li hr {
  border-color: #2d3a35 !important;
}

[data-theme="dark"] .admonition,
body[data-md-color-scheme="slate"] .admonition {
  background: #1a2421 !important;
  border-color: #2d3a35 !important;
  color: #e7e5e4 !important;
}

[data-theme="dark"] .admonition-title,
body[data-md-color-scheme="slate"] .admonition-title {
  background: #223029 !important;
  color: #6ee7b7 !important;
}

[data-theme="dark"] iframe.pdf-viewer,
body[data-md-color-scheme="slate"] iframe.pdf-viewer {
  border-color: #2d3a35 !important;
  background-color: #1a2421 !important;
}

/* ============================================================================
   Phase 4: Mobile & Diagram Responsiveness Enhancements
   ============================================================================ */

.tu-diagram-wrap {
  margin: 2rem 0;
  padding: 1.5rem;
  background: var(--card, #fff);
  border: 1px solid var(--border, #e2e8f0);
  border-radius: 12px;
  box-shadow: var(--shadow, 0 2px 6px rgba(0,0,0,.04));
  display: flex;
  flex-direction: column;
  align-items: center;
  overflow-x: auto;
}

.tu-diagram-wrap svg {
  max-width: 100%;
  height: auto;
  display: block;
}

.tu-diagram-caption {
  margin-top: 1rem;
  font-size: 0.88rem;
  color: var(--ink-muted, #64748b);
  text-align: center;
  font-style: italic;
}

.tu-table-wrap {
  width: 100%;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 1.5rem 0;
}

@media (max-width: 768px) {
  html {
    font-size: 18px !important;
  }
  .tu-topnav {
    overflow-x: auto;
    white-space: nowrap;
    -webkit-overflow-scrolling: touch;
    padding: 0.5rem 0.5rem;
    gap: 0.25rem;
  }
  .tu-nav-item {
    padding: 0.4rem 0.6rem;
    font-size: 0.85rem;
  }
  .tu-diagram-wrap {
    padding: 0.75rem;
  }
  .tu-term-card {
    padding: 1rem;
  }
}

/* === Formula Cards (Readable mathematical formulas) ================ */

.tu-formula-card {
  background: var(--card, #ffffff);
  border: 1px solid var(--border, #e2e8f0);
  border-left: 5px solid var(--accent, #059669);
  border-radius: 10px;
  padding: 1.25rem 1.5rem;
  margin: 1.5rem 0;
  box-shadow: 0 2px 4px rgba(0,0,0,0.04);
}

[data-theme="dark"] .tu-formula-card,
body[data-md-color-scheme="slate"] .tu-formula-card {
  background: #1a2421 !important;
  border-color: #2d3a35 !important;
  border-left-color: #10b981 !important;
  color: #e2e8f0 !important;
}

[data-theme="dark"] .tu-formula-card div[style*="accent-dark"],
body[data-md-color-scheme="slate"] .tu-formula-card div[style*="accent-dark"] {
  color: #34d399 !important;
}

[data-theme="dark"] .tu-formula-card ul li,
body[data-md-color-scheme="slate"] .tu-formula-card ul li {
  color: #cbd5e1 !important;
}