/* ByteByteGo Reader Engine - Artisanal High-Taste Typography & Responsive Navigation */

/* Lexica Ultralegible Web Fonts */
@font-face {
  font-family: 'Lexica Ultralegible';
  src: url('../fonts/lexica/LexicaUltralegible-Regular.woff2') format('woff2');
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Lexica Ultralegible';
  src: url('../fonts/lexica/LexicaUltralegible-Bold.woff2') format('woff2');
  font-weight: 700;
  font-style: normal;
  font-display: swap;
}

@font-face {
  font-family: 'Lexica Ultralegible';
  src: url('../fonts/lexica/LexicaUltralegible-Italic.woff2') format('woff2');
  font-weight: 400;
  font-style: italic;
  font-display: swap;
}

@font-face {
  font-family: 'Lexica Ultralegible';
  src: url('../fonts/lexica/LexicaUltralegible-BoldItalic.woff2') format('woff2');
  font-weight: 700;
  font-style: italic;
  font-display: swap;
}

:root {
  --bg-page: #FFFFFF;
  --bg-surface: #F8FAFC;
  --bg-sidebar: #0F172A;
  --bg-sidebar-hover: #1E293B;
  --bg-sidebar-active: #00BA83;
  --text-main: #0F172A;
  --text-muted: #64748B;
  --text-subtle: #94A3B8;
  --border-color: #E2E8F0;
  --border-subtle: #F1F5F9;
  --primary: #00BA83;
  --primary-hover: #009E6F;
  --primary-subtle: rgba(0, 186, 131, 0.1);
  --header-height: 54px;
  --sidebar-width: 310px;
  --reader-font: 'Lexica Ultralegible', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --reader-font-size: 16px;
  --reader-line-height: 1.75;
  --reader-max-width: 740px;
  --reader-text-align: left;
  --reader-hyphens: auto;
  --reader-mobile-pad: 14px;

  /* Code Section Theme (Light) */
  --code-bg: #F8FAFC;
  --code-header-bg: #EDF2F7;
  --code-border: #E2E8F0;
  --code-text: #0F172A;
  --code-tab-active-bg: #FFFFFF;
  --code-tab-active-text: #00BA83;
  --code-tab-inactive-text: #64748B;
  --code-copy-bg: rgba(0, 0, 0, 0.05);
  --code-copy-border: rgba(0, 0, 0, 0.1);
  --code-copy-text: #475569;
  --code-shadow: rgba(0, 0, 0, 0.04);
}

/* Sepia Theme */
[data-theme="sepia"] {
  --bg-page: #FBF0D9;
  --bg-surface: #F4E4C1;
  --bg-sidebar: #2D2013;
  --bg-sidebar-hover: #3D2C1B;
  --bg-sidebar-active: #8E5316;
  --text-main: #2D2013;
  --text-muted: #73573C;
  --text-subtle: #9E7D5D;
  --border-color: #E5D5B8;
  --border-subtle: #ECE1CD;
  --primary: #8E5316;
  --primary-hover: #724210;
  --primary-subtle: rgba(142, 83, 22, 0.14);

  /* Code Section Theme (Cream / Parchment) */
  --code-bg: #F4E4C1;
  --code-header-bg: #EBD7B0;
  --code-border: #E0CFAC;
  --code-text: #2D2013;
  --code-tab-active-bg: #FBF0D9;
  --code-tab-active-text: #8E5316;
  --code-tab-inactive-text: #73573C;
  --code-copy-bg: rgba(142, 83, 22, 0.08);
  --code-copy-border: rgba(142, 83, 22, 0.2);
  --code-copy-text: #8E5316;
  --code-shadow: rgba(142, 83, 22, 0.08);
}

/* Dark Theme (Charcoal Slate) */
[data-theme="dark"] {
  --bg-page: #0B0F19;
  --bg-surface: #111827;
  --bg-sidebar: #070A10;
  --bg-sidebar-hover: #1F2937;
  --bg-sidebar-active: #10B981;
  --text-main: #F1F5F9;
  --text-muted: #94A3B8;
  --text-subtle: #64748B;
  --border-color: #1F2937;
  --border-subtle: #161F2E;
  --primary: #10B981;
  --primary-hover: #059669;
  --primary-subtle: rgba(16, 185, 129, 0.15);

  /* Code Section Theme (Slate 900) */
  --code-bg: #111827;
  --code-header-bg: #1E293B;
  --code-border: #334155;
  --code-text: #F1F5F9;
  --code-tab-active-bg: #0F172A;
  --code-tab-active-text: #10B981;
  --code-tab-inactive-text: #94A3B8;
  --code-copy-bg: rgba(255, 255, 255, 0.08);
  --code-copy-border: rgba(255, 255, 255, 0.15);
  --code-copy-text: #E2E8F0;
  --code-shadow: rgba(0, 0, 0, 0.2);
}

/* OLED Black Theme */
[data-theme="oled"] {
  --bg-page: #000000;
  --bg-surface: #0A0A0A;
  --bg-sidebar: #000000;
  --bg-sidebar-hover: #141414;
  --bg-sidebar-active: #00E161;
  --text-main: #E5E7EB;
  --text-muted: #8892B0;
  --text-subtle: #555E75;
  --border-color: #1F1F1F;
  --border-subtle: #141414;
  --primary: #00E161;
  --primary-hover: #00C853;
  --primary-subtle: rgba(0, 225, 97, 0.15);

  /* Code Section Theme (Pitch Black) */
  --code-bg: #050505;
  --code-header-bg: #121212;
  --code-border: #262626;
  --code-text: #E5E7EB;
  --code-tab-active-bg: #1A1A1A;
  --code-tab-active-text: #00E161;
  --code-tab-inactive-text: #8892B0;
  --code-copy-bg: rgba(255, 255, 255, 0.08);
  --code-copy-border: rgba(255, 255, 255, 0.15);
  --code-copy-text: #E5E7EB;
  --code-shadow: rgba(0, 0, 0, 0.5);
}

/* Base resets & typography */
*, *::before, *::after {
  box-sizing: border-box;
}

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  background-color: var(--bg-page);
  color: var(--text-main);
  font-family: var(--reader-font);
  font-size: var(--reader-font-size);
  line-height: var(--reader-line-height);
  margin: 0;
  padding: 0;
  transition: background-color 0.2s ease, color 0.2s ease;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  min-height: 100vh;
}

/* Top Navigation Header */
.bbg-header {
  position: sticky;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background: var(--bg-page);
  border-bottom: 1px solid var(--border-color);
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  transition: background-color 0.2s ease, border-color 0.2s ease;
}

.bbg-header-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  flex-shrink: 0;
}

.bbg-header-logo img {
  height: 24px;
  width: auto;
  display: block;
}

.bbg-catalog-badge {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  background: var(--primary-subtle);
  color: var(--primary);
  padding: 3px 8px;
  border-radius: 999px;
  transition: all 0.2s ease;
}

.bbg-header-logo:hover .bbg-catalog-badge {
  background: var(--primary);
  color: #FFFFFF;
}

.bbg-header-title-wrap {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  color: var(--text-muted);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  max-width: 50%;
}

.bbg-header-course {
  font-weight: 600;
  color: var(--text-main);
  flex-shrink: 0;
}

.bbg-header-sep {
  color: var(--border-color);
  font-size: 14px;
}

.bbg-header-chapter {
  color: var(--text-muted);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.bbg-header-controls {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-shrink: 0;
}

.bbg-ctrl-btn {
  background: none;
  border: 1px solid transparent;
  color: var(--text-muted);
  height: 36px;
  padding: 0 10px;
  border-radius: 8px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  font-weight: 600;
  transition: all 0.15s ease;
}

.bbg-ctrl-btn:hover {
  background: var(--bg-surface);
  border-color: var(--border-color);
  color: var(--text-main);
}

.bbg-ctrl-btn svg {
  width: 17px;
  height: 17px;
  stroke: currentColor;
  stroke-width: 2;
  fill: none;
}

.ctrl-aa {
  font-family: Georgia, serif;
  font-weight: 700;
  font-size: 15px;
  line-height: 1;
}

/* Circular Theme Swatch Icon (fills with current theme color) */
.bbg-theme-swatch {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: #FFFFFF;
  border: 2px solid var(--primary);
  display: inline-block;
  box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.15);
  flex-shrink: 0;
  transition: all 0.2s ease;
}

[data-theme="sepia"] .bbg-theme-swatch {
  background: #F4E4C1;
  border-color: #8E5316;
  box-shadow: 0 0 0 1px rgba(142, 83, 22, 0.3);
}

[data-theme="dark"] .bbg-theme-swatch {
  background: #111827;
  border-color: #10B981;
  box-shadow: 0 0 0 1px rgba(255, 255, 255, 0.2);
}

[data-theme="oled"] .bbg-theme-swatch {
  background: #000000;
  border-color: #00E161;
  box-shadow: 0 0 0 1px rgba(255, 255, 255, 0.3);
}

/* Layout */
.bbg-layout {
  display: flex;
  min-height: calc(100vh - var(--header-height));
  position: relative;
}

/* TOC Sidebar */
.bbg-sidebar {
  width: var(--sidebar-width);
  background: var(--bg-sidebar);
  color: #F1F5F9;
  flex-shrink: 0;
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  height: calc(100vh - var(--header-height));
  position: sticky;
  top: var(--header-height);
  z-index: 100;
  overflow: hidden;
  transition: margin-left 0.25s cubic-bezier(0.16, 1, 0.3, 1), opacity 0.2s ease, transform 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

@media (min-width: 769px) {
  body.sidebar-collapsed .bbg-sidebar {
    margin-left: calc(-1 * var(--sidebar-width));
    opacity: 0;
    pointer-events: none;
  }

  body.sidebar-collapsed #bbgBtnToc {
    background: var(--primary-subtle);
    color: var(--primary);
    border-color: var(--primary);
  }
}

.bbg-sidebar-header {
  padding: 14px 16px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  display: flex;
  flex-direction: column;
  gap: 10px;
  flex-shrink: 0;
}

.bbg-sidebar-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: #FFFFFF;
}

.bbg-sidebar-progress {
  font-size: 11px;
  font-weight: 700;
  color: var(--primary);
  background: rgba(0, 186, 131, 0.15);
  padding: 2px 7px;
  border-radius: 999px;
}

.bbg-sider-close {
  display: none;
  background: none;
  border: none;
  color: #94A3B8;
  font-size: 15px;
  cursor: pointer;
  padding: 2px 6px;
}

.bbg-sidebar-search {
  width: 100%;
  background: rgba(255, 255, 255, 0.07);
  border: 1px solid rgba(255, 255, 255, 0.12);
  border-radius: 6px;
  padding: 7px 10px;
  color: #FFFFFF;
  font-size: 12px;
  outline: none;
  transition: border-color 0.2s ease;
}

.bbg-sidebar-search:focus {
  border-color: var(--primary);
}

.bbg-sidebar-search::placeholder {
  color: #64748B;
}

.bbg-sidebar-list {
  list-style: none;
  margin: 0;
  padding: 8px;
  overflow-y: auto;
  flex-grow: 1;
}

.bbg-sidebar-list::-webkit-scrollbar {
  width: 5px;
}
.bbg-sidebar-list::-webkit-scrollbar-thumb {
  background: rgba(255, 255, 255, 0.15);
  border-radius: 4px;
}

.bbg-chapter-anchor {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 9px 12px;
  border-radius: 6px;
  text-decoration: none;
  color: #94A3B8;
  font-size: 13px;
  line-height: 1.4;
  transition: all 0.15s ease;
  margin-bottom: 2px;
}

.bbg-chapter-anchor:hover {
  background: rgba(255, 255, 255, 0.06);
  color: #FFFFFF;
}

.bbg-chapter-anchor.active {
  background: var(--bg-sidebar-active);
  color: #FFFFFF !important;
  font-weight: 600;
}

.bbg-chapter-anchor.active .bbg-chapter-num {
  color: #FFFFFF !important;
  opacity: 0.85;
}

.bbg-chapter-num {
  font-size: 11px;
  font-family: monospace;
  font-weight: 700;
  color: var(--primary);
  margin-right: 10px;
  flex-shrink: 0;
}

/* Main Content Area */
.bbg-main {
  flex-grow: 1;
  min-width: 0;
  padding: 40px 32px 80px;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.bbg-article {
  width: 100%;
  max-width: var(--reader-max-width);
  margin: 0 auto;
  transition: max-width 0.2s ease;
}

/* Chapter Number Badge (original ByteByteGo prominent green 00, 01, 02) */
.bbg-article strong[class*="chapter"],
.bbg-article .style_chapter___jdu8,
.bbg-article .style_chapter__grtAe,
.bbg-article .style-module-scss-module__nbagBW__chapter,
.bbg-chapter-num-badge {
  display: block;
  font-size: 28px;
  font-weight: 800;
  line-height: 1;
  color: var(--primary) !important;
  letter-spacing: -0.03em;
  margin-top: 4px;
  margin-bottom: 8px;
  font-family: inherit;
}

/* Optical scaling for Monospace font to balance x-height with proportional fonts */
[data-font="mono"] .bbg-article,
.bbg-article[data-font="mono"] {
  font-size: calc(var(--reader-font-size) * 0.91);
  letter-spacing: -0.01em;
}

/* Article Typography */
.bbg-article h1 {
  font-size: 2.25rem;
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -0.025em;
  margin-top: 0;
  margin-bottom: 24px;
  color: var(--text-main);
}

.bbg-article h2 {
  font-size: 1.5rem;
  font-weight: 700;
  line-height: 1.3;
  letter-spacing: -0.015em;
  margin-top: 40px;
  margin-bottom: 16px;
  color: var(--text-main);
  border-bottom: 1px solid var(--border-subtle);
  padding-bottom: 8px;
}

.bbg-article h3 {
  font-size: 1.25rem;
  font-weight: 700;
  line-height: 1.35;
  margin-top: 32px;
  margin-bottom: 12px;
  color: var(--text-main);
}

.bbg-article h4, .bbg-article h5, .bbg-article h6 {
  font-size: 1.05rem;
  font-weight: 700;
  margin-top: 24px;
  margin-bottom: 8px;
  color: var(--text-main);
}

.bbg-article p {
  margin-top: 0;
  margin-bottom: 20px;
  text-align: var(--reader-text-align, left);
  hyphens: var(--reader-hyphens, auto);
  -webkit-hyphens: var(--reader-hyphens, auto);
  text-justify: inter-word;
}

.bbg-article li {
  margin-bottom: 8px;
  text-align: var(--reader-text-align, left);
  hyphens: var(--reader-hyphens, auto);
  -webkit-hyphens: var(--reader-hyphens, auto);
}

.bbg-article ul, .bbg-article ol {
  margin-top: 0;
  margin-bottom: 20px;
  padding-left: 24px;
}

.bbg-article li {
  margin-bottom: 8px;
}

.bbg-article hr {
  border: none;
  height: 1px;
  background: var(--border-color);
  margin: 40px 0;
}

.bbg-article blockquote {
  margin: 24px 0;
  padding: 12px 20px;
  border-left: 4px solid var(--primary);
  background: var(--bg-surface);
  border-radius: 0 8px 8px 0;
  color: var(--text-muted);
}

.bbg-article table {
  width: 100%;
  border-collapse: collapse;
  margin: 28px 0;
  font-size: 14px;
}

.bbg-article th, .bbg-article td {
  padding: 10px 14px;
  border: 1px solid var(--border-color);
  text-align: left;
}

.bbg-article th {
  background: var(--bg-surface);
  font-weight: 700;
}

/* Figures and Technical Diagrams */
.diagram-figure {
  margin: 32px 0;
  padding: 20px;
  background: #FFFFFF;
  border: 1px solid var(--border-color);
  border-radius: 12px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.05);
  box-sizing: border-box;
}

.diagram-figure img {
  max-width: 100%;
  height: auto;
  display: block;
  object-fit: contain;
  border-radius: 4px;
}

.diagram-figure figcaption {
  margin-top: 12px;
  font-size: 12.5px;
  font-weight: 600;
  color: #64748B;
  text-align: center;
}

/* Code Blocks & Cards */
.code-block-card {
  margin: 26px 0;
  border-radius: 10px;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  overflow: hidden;
  box-shadow: 0 2px 8px var(--code-shadow);
  transition: background-color 0.2s ease, border-color 0.2s ease;
}

.code-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 6px 12px;
  background: var(--code-header-bg);
  border-bottom: 1px solid var(--code-border);
  gap: 8px;
}

.code-lang-tabs {
  display: flex;
  align-items: center;
  gap: 4px;
}

.code-tab-btn {
  background: none;
  border: 1px solid transparent;
  padding: 4px 10px;
  border-radius: 6px;
  font-size: 12px;
  font-weight: 600;
  color: var(--code-tab-inactive-text);
  cursor: pointer;
  transition: all 0.15s ease;
  line-height: 1.3;
}

.code-tab-btn:hover {
  color: var(--code-text);
}

.code-tab-btn.active {
  background: var(--code-tab-active-bg);
  color: var(--code-tab-active-text);
  border-color: var(--code-border);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.06);
}

.code-lang-badge {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--code-tab-active-text);
  padding: 3px 6px;
}

.code-copy-btn {
  background: var(--code-copy-bg);
  border: 1px solid var(--code-copy-border);
  color: var(--code-copy-text);
  font-size: 12px;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: 6px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 5px;
  transition: all 0.15s ease;
  flex-shrink: 0;
}

.code-copy-btn:hover {
  filter: brightness(0.95);
}

.code-pane {
  display: none;
}

.code-pane.active {
  display: block;
}

.code-pane pre, .code-block-card.simple pre {
  margin: 0;
  padding: 16px;
  overflow-x: auto;
  font-family: 'JetBrains Mono', Consolas, Monaco, monospace;
  font-size: 13.5px;
  line-height: 1.6;
  color: var(--code-text);
  background: transparent;
}

.code-block-card code {
  font-family: inherit;
  font-size: inherit;
  color: inherit;
}

/* Inline Code */
p code, li code {
  font-family: 'JetBrains Mono', Consolas, Monaco, monospace;
  font-size: 0.88em;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  padding: 2px 5px;
  border-radius: 4px;
  color: var(--primary);
}

/* Bottom Prev / Next Cards */
.bbg-bottom-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  width: 100%;
  max-width: var(--reader-max-width);
  margin-top: 48px;
  padding-top: 28px;
  border-top: 1px solid var(--border-color);
}

.bbg-nav-card {
  display: flex;
  flex-direction: column;
  padding: 16px;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 10px;
  text-decoration: none;
  color: inherit;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

.bbg-nav-card:hover {
  border-color: var(--primary);
  transform: translateY(-2px);
}

.bbg-nav-card.next {
  text-align: right;
  align-items: flex-end;
}

.nav-sub {
  font-size: 11.5px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--primary);
  margin-bottom: 4px;
}

.nav-title {
  font-size: 14px;
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.35;
}

/* Settings Modal */
.bbg-settings-modal {
  display: none;
  position: fixed;
  top: calc(var(--header-height) + 10px);
  right: 16px;
  width: 320px;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.15), 0 8px 10px -6px rgba(0, 0, 0, 0.1);
  padding: 16px;
  z-index: 1050;
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
}

.bbg-settings-modal.open {
  display: block;
}

.bbg-settings-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 13px;
  font-weight: 700;
  margin-bottom: 14px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
}

.bbg-modal-close {
  background: none;
  border: none;
  color: var(--text-muted);
  font-size: 14px;
  cursor: pointer;
  padding: 2px 6px;
}

.bbg-setting-row {
  margin-bottom: 14px;
}

.bbg-row-label {
  display: block;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--text-muted);
  margin-bottom: 6px;
}

.bbg-btn-group {
  display: flex;
  background: rgba(0, 0, 0, 0.04);
  padding: 3px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
}

.bbg-group-btn {
  flex: 1;
  background: none;
  border: none;
  padding: 6px 4px;
  font-size: 12px;
  font-weight: 600;
  color: var(--text-muted);
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
  text-align: center;
}

.bbg-group-btn.active {
  background: var(--bg-page);
  color: var(--text-main);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

/* Typeface Grid - Visual Font Previews */
#bbgFontGroup {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
  background: none;
  border: none;
  padding: 0;
}

#bbgFontGroup .bbg-group-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 7px 4px 6px;
  border-radius: 6px;
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  cursor: pointer;
  text-align: center;
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
  min-height: 52px;
}

#bbgFontGroup .bbg-group-btn:hover {
  transform: translateY(-1px);
  border-color: var(--primary);
}

#bbgFontGroup .bbg-group-btn.active {
  background: var(--bg-page);
  border-color: var(--primary);
  box-shadow: 0 0 0 2px var(--primary);
  color: var(--text-main);
}

/* Individual Font Application directly on option labels & samples */
#bbgFontGroup .bbg-group-btn[data-f="lexica"],
[data-f="lexica"] .bbg-font-sample,
[data-f="lexica"] .bbg-font-name {
  font-family: 'Lexica Ultralegible', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif !important;
}

#bbgFontGroup .bbg-group-btn[data-f="system"],
[data-f="system"] .bbg-font-sample,
[data-f="system"] .bbg-font-name {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif !important;
}

#bbgFontGroup .bbg-group-btn[data-f="serif"],
[data-f="serif"] .bbg-font-sample,
[data-f="serif"] .bbg-font-name {
  font-family: Georgia, Cambria, 'Times New Roman', serif !important;
}

#bbgFontGroup .bbg-group-btn[data-f="mono"],
[data-f="mono"] .bbg-font-sample,
[data-f="mono"] .bbg-font-name {
  font-family: 'JetBrains Mono', Consolas, Monaco, monospace !important;
}

.bbg-font-sample {
  display: block;
  font-size: 16px;
  font-weight: 700;
  line-height: 1.1;
  margin-bottom: 2px;
  pointer-events: none;
}

.bbg-font-name {
  display: block;
  font-size: 11px;
  font-weight: 600;
  opacity: 0.9;
  pointer-events: none;
}

.bbg-theme-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
}

.bbg-theme-chip {
  padding: 8px 4px;
  font-size: 11px;
  font-weight: 700;
  border-radius: 6px;
  cursor: pointer;
  text-align: center;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.bbg-theme-chip:hover {
  transform: translateY(-1px);
}

.bbg-theme-chip.active {
  box-shadow: 0 0 0 2px var(--primary);
}

/* Direct Font Size Stepper & Slider */
.bbg-size-control-wrap {
  display: flex;
  align-items: center;
  gap: 8px;
  background: rgba(0, 0, 0, 0.04);
  padding: 4px 6px;
  border-radius: 8px;
  border: 1px solid var(--border-color);
}

.bbg-size-btn {
  background: var(--bg-page);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  font-size: 13px;
  font-weight: 700;
  width: 32px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
  cursor: pointer;
  flex-shrink: 0;
  transition: all 0.15s ease;
}

.bbg-size-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.bbg-size-slider-wrap {
  flex: 1;
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 0 4px;
}

.bbg-size-slider {
  flex: 1;
  height: 4px;
  accent-color: var(--primary);
  cursor: pointer;
}

.bbg-size-badge {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  font-size: 12px;
  font-weight: 700;
  padding: 3px 6px;
  border-radius: 5px;
  min-width: 44px;
  text-align: center;
  cursor: pointer;
}

.bbg-size-badge:hover {
  border-color: var(--primary);
}

/* Settings Modal Footer & Reset Button */
.bbg-settings-footer {
  margin-top: 14px;
  padding-top: 10px;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: flex-end;
}

.bbg-reset-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: none;
  border: 1px solid var(--border-color);
  color: var(--text-muted);
  font-size: 11px;
  font-weight: 600;
  padding: 5px 10px;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.bbg-reset-btn:hover {
  background: var(--bg-surface);
  border-color: var(--primary);
  color: var(--primary);
}

/* Try It Yourself / Open Code Editor Banner */
.style_tryBanner__WFMKc {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-left: 4px solid var(--primary);
  border-radius: 12px;
  padding: 16px 20px;
  margin: 28px 0;
  box-shadow: 0 4px 16px var(--code-shadow);
  flex-wrap: wrap;
}

.style_tryTitle__dVqce {
  font-size: 15px;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 4px;
}

.style_tryDesc___lKzS {
  font-size: 13px;
  color: var(--text-muted);
  line-height: 1.45;
}

.style_openBtn__F_m3N,
.style_tryBanner__WFMKc button.ant-btn {
  display: inline-flex !important;
  align-items: center !important;
  gap: 8px !important;
  background: var(--primary) !important;
  color: #FFFFFF !important;
  border: none !important;
  font-size: 13px !important;
  font-weight: 700 !important;
  padding: 9px 18px !important;
  border-radius: 8px !important;
  cursor: pointer !important;
  text-decoration: none !important;
  transition: all 0.2s ease !important;
  white-space: nowrap !important;
  box-shadow: 0 2px 6px rgba(0, 186, 131, 0.2) !important;
}

.style_openBtn__F_m3N:hover,
.style_tryBanner__WFMKc button.ant-btn:hover {
  background: var(--primary-hover) !important;
  transform: translateY(-1px) !important;
  box-shadow: 0 4px 12px rgba(0, 186, 131, 0.35) !important;
}

/* Fast Course Switcher */
.bbg-course-switcher-btn {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  background: var(--primary-subtle);
  color: var(--primary);
  border: 1px solid transparent;
  padding: 4px 9px;
  border-radius: 999px;
  font-size: 11px;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.2s ease;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.bbg-course-switcher-btn:hover {
  background: var(--primary);
  color: #FFFFFF;
}

.bbg-course-switcher-btn svg {
  transition: transform 0.2s ease;
}

.bbg-course-switcher-btn.open svg {
  transform: rotate(180deg);
}

.bbg-course-modal {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 1060;
  align-items: flex-start;
  justify-content: flex-start;
}

.bbg-course-modal.open {
  display: flex;
}

.bbg-course-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(15, 23, 42, 0.4);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  animation: fadeIn 0.18s ease-out;
}

.bbg-course-sheet {
  position: absolute;
  top: calc(var(--header-height) + 8px);
  left: 16px;
  width: 360px;
  max-height: calc(100vh - var(--header-height) - 30px);
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: 14px;
  box-shadow: 0 16px 36px rgba(0, 0, 0, 0.2);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  z-index: 1061;
  animation: modalScaleUp 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

.bbg-course-sheet-header {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--bg-surface);
}

.bbg-course-sheet-title {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-muted);
}

.bbg-course-sheet-list {
  padding: 8px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.bbg-course-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 12px;
  border-radius: 8px;
  text-decoration: none;
  color: var(--text-main);
  transition: all 0.15s ease;
}

.bbg-course-item:hover {
  background: var(--bg-page);
  color: var(--primary);
  transform: translateX(2px);
}

.bbg-course-item.active {
  background: var(--primary-subtle);
  color: var(--primary);
  font-weight: 700;
}

.bbg-course-item-left {
  display: flex;
  align-items: center;
  gap: 10px;
  min-width: 0;
}

.bbg-course-item-num {
  font-size: 11px;
  font-weight: 700;
  color: var(--text-subtle);
  font-family: monospace;
  width: 18px;
}

.bbg-course-item.active .bbg-course-item-num {
  color: var(--primary);
}

.bbg-course-item-name {
  font-size: 13px;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.bbg-course-item-count {
  font-size: 11px;
  color: var(--text-muted);
  flex-shrink: 0;
  padding-left: 8px;
}

.bbg-course-sheet-footer {
  padding: 10px 14px;
  border-top: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--bg-surface);
}

.bbg-course-all-link {
  font-size: 12px;
  font-weight: 700;
  color: var(--primary);
  text-decoration: none;
}

.bbg-course-all-link:hover {
  text-decoration: underline;
}

/* Mobile Bottom Navigation Bar */
.bbg-reader-bottom-bar {
  display: none;
}

.bbg-drawer-backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  z-index: 998;
}

/* Responsive Breakpoints */
@media (max-width: 900px) {
  .bbg-sidebar {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    height: 100vh;
    transform: translateX(-100%);
    z-index: 1001;
    box-shadow: 4px 0 24px rgba(0, 0, 0, 0.25);
  }

  body.sider-open .bbg-sidebar {
    transform: translateX(0);
  }

  body.sider-open .bbg-drawer-backdrop {
    display: block;
  }

  .bbg-sider-close {
    display: block;
  }

  .bbg-main {
    padding: 24px 20px 80px;
  }

  .bbg-header-title-wrap {
    display: none;
  }
}

@media (max-width: 600px) {
  body {
    padding-bottom: 64px !important;
  }

  .bbg-header {
    height: 48px;
    padding: 0 10px;
    max-width: 100vw;
    box-sizing: border-box;
    overflow: hidden;
  }

  .bbg-header-controls {
    gap: 4px;
    flex-shrink: 0;
  }

  .bbg-ctrl-btn {
    padding: 0 6px !important;
    height: 32px !important;
    min-width: 32px !important;
    justify-content: center !important;
    gap: 0 !important;
  }

  .bbg-ctrl-btn .ctrl-label {
    display: none !important;
  }

  @media (max-width: 480px) {
    .bbg-header {
      padding: 0 8px;
    }
    .bbg-header-controls {
      gap: 3px;
    }
    .bbg-header-controls #bbgBtnToc {
      display: none !important;
    }
  }

  .bbg-header-logo img {
    height: 20px;
  }

  .bbg-catalog-badge {
    display: inline-flex !important;
    font-size: 10px;
    padding: 3px 8px;
    margin-left: 2px;
  }

  .bbg-main {
    padding: 18px var(--reader-mobile-pad, 14px) 72px;
  }

  .bbg-article h1 {
    font-size: 1.65rem;
    margin-bottom: 16px;
  }

  .bbg-article h2 {
    font-size: 1.3rem;
    margin-top: 28px;
    margin-bottom: 12px;
  }

  .diagram-figure {
    margin: 20px 0;
    padding: 12px;
  }

  .bbg-bottom-nav {
    grid-template-columns: 1fr;
    gap: 12px;
    margin-top: 36px;
    padding-top: 20px;
  }

  .bbg-nav-card.next {
    text-align: left;
    align-items: flex-start;
  }

  /* Sticky Mobile Bottom Navigation */
  .bbg-reader-bottom-bar {
    display: flex;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    height: 54px;
    background: var(--bg-surface);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-top: 1px solid var(--border-color);
    z-index: 995;
    align-items: center;
    justify-content: space-around;
    padding: 0 4px;
  }

  .bbg-bottom-bar-btn {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: none;
    border: none;
    color: var(--text-muted);
    min-width: 48px;
    min-height: 48px;
    cursor: pointer;
    gap: 2px;
    font-size: 10px;
    font-weight: 600;
  }

  .bbg-bottom-bar-btn svg {
    width: 19px;
    height: 19px;
    stroke: currentColor;
    stroke-width: 2;
    fill: none;
  }

  .bbg-bottom-bar-btn:active {
    color: var(--primary);
  }

  .bbg-settings-modal {
    top: auto;
    bottom: 60px;
    left: 12px;
    right: 12px;
    width: auto;
  }

  .bbg-course-modal {
    align-items: flex-end;
    justify-content: center;
  }

  .bbg-course-sheet {
    top: auto;
    left: 0;
    right: 0;
    bottom: 0;
    width: 100%;
    max-width: 100%;
    border-radius: 20px 20px 0 0;
    max-height: 80vh;
    animation: sheetSlideUp 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  }
}