/* ==========================================================================
   DESIGN SYSTEM & VARIABLES
   ========================================================================== */
:root {
  /* Colors - Light Theme (Elegant Editorial Cream) */
  --bg-primary: #FAF8F5;
  --bg-sidebar-left: #F4F0EA;
  --bg-sidebar-right: #F9F6F0;
  --text-primary: #2C2A29;
  --text-secondary: #6B6865;
  --text-muted: #9E9B97;
  --border-color: rgba(0, 0, 0, 0.07);
  --card-bg: #FFFFFF;
  --card-bg-glass: rgba(255, 255, 255, 0.7);
  --active-article-bg: rgba(197, 155, 39, 0.06);
  --active-article-border: #C59B27;
  
  /* Accents */
  --primary-accent: #1E2D3D; /* Deep Navy */
  --secondary-accent: #C59B27; /* Rich Amber Gold */
  --primary-accent-rgb: 30, 45, 61;
  --secondary-accent-rgb: 197, 155, 39;
  
  /* Semantic Colors */
  --color-success: #2E7D32;
  --color-success-bg: rgba(46, 125, 50, 0.08);
  --color-warning: #EF6C00;
  --color-warning-bg: rgba(239, 108, 0, 0.08);
  --color-danger: #C62828;
  --color-danger-bg: rgba(198, 40, 40, 0.08);
  --color-info: #1565C0;
  --color-info-bg: rgba(21, 101, 192, 0.08);
  
  /* Fonts */
  --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
  --font-serif: 'Lora', Georgia, 'Times New Roman', serif;
  --font-header: 'Outfit', sans-serif;
  
  /* Details */
  --border-radius-sm: 6px;
  --border-radius-md: 12px;
  --border-radius-lg: 20px;
  --box-shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.04);
  --box-shadow-md: 0 4px 16px rgba(0, 0, 0, 0.06);
  --box-shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.08);
  --transition-speed: 0.25s;
}

.dark-mode {
  /* Colors - Dark Theme (Premium Obsidian / Charcoal) */
  --bg-primary: #0F141C;
  --bg-sidebar-left: #161A22;
  --bg-sidebar-right: #12161E;
  --text-primary: #E5E9EC;
  --text-secondary: #9AA3AC;
  --text-muted: #646E78;
  --border-color: rgba(255, 255, 255, 0.08);
  --card-bg: #1B212C;
  --card-bg-glass: rgba(27, 33, 44, 0.7);
  --active-article-bg: rgba(229, 183, 61, 0.08);
  --active-article-border: #E5B73D;
  
  /* Accents */
  --primary-accent: #388BFD; /* Bright Electric Blue */
  --secondary-accent: #E5B73D; /* Lighter Gold */
  --primary-accent-rgb: 56, 139, 253;
  --secondary-accent-rgb: 229, 183, 61;
  
  /* Semantic Colors */
  --color-success: #4CAF50;
  --color-success-bg: rgba(76, 175, 80, 0.15);
  --color-warning: #FF9800;
  --color-warning-bg: rgba(255, 152, 0, 0.15);
  --color-danger: #F44336;
  --color-danger-bg: rgba(244, 67, 54, 0.15);
  --color-info: #2196F3;
  --color-info-bg: rgba(33, 150, 243, 0.15);
  
  --box-shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.2);
  --box-shadow-md: 0 4px 16px rgba(0, 0, 0, 0.3);
  --box-shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.4);
}

/* ==========================================================================
   BASE STYLES
   ========================================================================== */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  overflow: hidden;
  height: 100vh;
  width: 100vw;
  line-height: 1.5;
  transition: background-color var(--transition-speed), color var(--transition-speed);
}

/* ==========================================================================
   APP LAYOUT (Three Panel Grid)
   ========================================================================== */
#app-container {
  display: grid;
  grid-template-columns: 310px 1fr 420px;
  height: 100vh;
  width: 100vw;
  overflow: hidden;
}

/* Responsive drawer toggle buttons (hidden on desktop) */
.drawer-toggle-btn {
  display: none;
  align-items: center;
  gap: 6px;
  background: var(--card-bg);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  border-radius: var(--border-radius-sm);
  padding: 7px 12px;
  cursor: pointer;
  font-family: var(--font-sans);
  font-size: 0.78rem;
  font-weight: 600;
  white-space: nowrap;
  flex-shrink: 0;
  transition: background 0.2s, box-shadow 0.2s;
  box-shadow: var(--box-shadow-sm);
}
.drawer-toggle-btn:hover {
  background: var(--bg-sidebar-left);
  box-shadow: var(--box-shadow-md);
}
.drawer-toggle-btn svg {
  flex-shrink: 0;
}

/* Backdrop for closing drawers on tap-outside */
#drawer-backdrop {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  z-index: 99;
  backdrop-filter: blur(2px);
  -webkit-backdrop-filter: blur(2px);
  animation: fadeIn 0.2s ease;
}
#drawer-backdrop.active {
  display: block;
}

/* ≤1100px: Collapse right panel into a slide-in drawer */
@media (max-width: 1100px) {
  #app-container {
    grid-template-columns: 280px 1fr 0px;
  }
  #sidebar-right {
    position: fixed;
    right: -440px;
    top: 0;
    bottom: 0;
    width: 420px;
    z-index: 100;
    box-shadow: var(--box-shadow-lg);
    transition: right 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    overflow-y: auto;
  }
  #sidebar-right.active {
    right: 0;
  }
  /* Show Study Center button in header */
  #sidebar-right-toggle {
    display: flex;
  }
  /* Header flex layout for the three-element row */
  .content-header {
    display: flex;
    align-items: center;
    gap: 12px;
  }
  .header-center-block {
    flex: 1;
    min-width: 0;
  }
  #sidebar-left-toggle {
    display: none;
  }
}

/* ≤768px: Also collapse left panel into a slide-in drawer */
@media (max-width: 768px) {
  #app-container {
    grid-template-columns: 0px 1fr 0px;
  }
  #sidebar-left {
    position: fixed;
    left: -320px;
    top: 0;
    bottom: 0;
    width: 310px;
    z-index: 101;
    box-shadow: var(--box-shadow-lg);
    transition: left 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    overflow-y: auto;
  }
  #sidebar-left.active {
    left: 0;
  }
  /* Show hamburger on mobile */
  #sidebar-left-toggle {
    display: flex;
  }
  #sidebar-right-toggle {
    display: flex;
  }
}


/* ==========================================================================
   LEFT SIDEBAR (TOC & Search)
   ========================================================================== */
#sidebar-left {
  background-color: var(--bg-sidebar-left);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  height: 100%;
  overflow: hidden;
}

.sidebar-header {
  padding: 24px 20px 16px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo-area {
  font-family: var(--font-header);
  font-weight: 800;
  font-size: 1.15rem;
  letter-spacing: -0.5px;
}

.logo-accent {
  color: var(--secondary-accent);
  background: rgba(var(--secondary-accent-rgb), 0.15);
  padding: 2px 6px;
  border-radius: 4px;
  margin-right: 4px;
}

/* Progress Section */
.progress-container {
  padding: 0 20px 16px 20px;
  border-bottom: 1px solid var(--border-color);
}

.progress-info {
  display: flex;
  justify-content: space-between;
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

.progress-bar-bg {
  height: 6px;
  background-color: var(--border-color);
  border-radius: 3px;
  overflow: hidden;
  margin-bottom: 4px;
}

#progress-bar-fill {
  height: 100%;
  background-color: var(--secondary-accent);
  border-radius: 3px;
  transition: width 0.4s ease;
}

.progress-stats {
  font-size: 0.75rem;
  color: var(--text-muted);
}

/* Search Area */
.search-area {
  padding: 16px 20px;
  border-bottom: 1px solid var(--border-color);
}

.search-box {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  display: flex;
  align-items: center;
  padding: 8px 12px;
  margin-bottom: 12px;
  box-shadow: var(--box-shadow-sm);
  transition: border-color 0.2s;
}

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

.search-icon {
  color: var(--text-muted);
  margin-right: 8px;
}

.search-box input {
  background: none;
  border: none;
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.85rem;
  width: 100%;
  outline: none;
}

.filter-toggles {
  display: flex;
  gap: 8px;
}

.filter-tab-btn {
  flex: 1;
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-family: var(--font-sans);
  font-size: 0.75rem;
  font-weight: 600;
  padding: 6px 10px;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  box-shadow: var(--box-shadow-sm);
  transition: background-color 0.2s, border-color 0.2s, color 0.2s;
}

.filter-tab-btn:hover {
  background-color: var(--bg-primary);
  color: var(--text-primary);
}

.filter-tab-btn.active {
  background: rgba(var(--secondary-accent-rgb), 0.15);
  border-color: var(--secondary-accent);
  color: var(--secondary-accent);
}

.filter-tab-btn.secondary.active {
  background: rgba(var(--primary-accent-rgb), 0.15);
  border-color: var(--primary-accent);
  color: var(--primary-accent);
}

.bookmark-badge {
  font-size: 0.65rem;
  background-color: var(--border-color);
  color: var(--text-secondary);
  padding: 2px 6px;
  border-radius: 4px;
  font-weight: 700;
  min-width: 18px;
  text-align: center;
  line-height: 1.2;
  transition: background-color 0.2s, color 0.2s;
}

.filter-tab-btn.active .bookmark-badge {
  background-color: var(--secondary-accent);
  color: var(--bg-primary);
}

/* Table of Contents Lists */
#table-of-contents {
  flex: 1;
  overflow-y: auto;
  padding: 16px 8px;
}

/* TOC Expand/Collapse Inline Actions */
.toc-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 10px 10px 10px;
  border-bottom: 1px solid var(--border-color);
  margin-bottom: 8px;
}

.toc-header-title {
  font-family: var(--font-header);
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-muted);
}

.toc-actions {
  display: flex;
  align-items: center;
  gap: 6px;
}

.toc-action-btn {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  cursor: pointer;
  padding: 4px;
  border-radius: 4px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--box-shadow-sm);
  transition: all 0.2s ease;
}

.toc-action-btn:hover {
  color: var(--text-primary);
  background-color: var(--bg-primary);
  border-color: var(--text-secondary);
  transform: translateY(-1px);
}

.toc-action-btn:active {
  transform: translateY(0);
}

.toc-action-btn svg {
  display: block;
}

/* Tree Structure Nesting Guidelines */
#toc-tree-container details {
  margin-top: 2px;
}

#toc-tree-container details[open] > details,
#toc-tree-container details[open] > ul.toc-article-list {
  margin-left: 12px;
  border-left: 1px dashed var(--border-color);
  padding-left: 8px;
}

/* Summary Base Styles & Marker Removal */
#toc-tree-container summary {
  display: flex;
  align-items: center;
  list-style: none;
  cursor: pointer;
  user-select: none;
  padding: 6px 10px;
  border-radius: var(--border-radius-sm);
  margin-bottom: 2px;
  transition: background-color 0.2s, color 0.2s;
}

#toc-tree-container summary::-webkit-details-marker {
  display: none;
}

/* Custom SVG Chevron Styling and Rotation */
.toc-chevron {
  margin-right: 6px;
  transition: transform var(--transition-speed) ease;
  color: var(--text-muted);
  flex-shrink: 0;
}

details[open] > summary > .toc-chevron {
  transform: rotate(90deg);
  color: var(--secondary-accent);
}

/* Specific Summaries Stylings by Level */
.toc-book-summary {
  font-family: var(--font-header);
  font-weight: 700;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-primary);
  margin-top: 6px;
}

.toc-book-summary:hover {
  background-color: rgba(0, 0, 0, 0.04);
}

.dark-mode .toc-book-summary:hover {
  background-color: rgba(255, 255, 255, 0.04);
}

.toc-title-summary {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 0.8rem;
  color: var(--text-secondary);
}

.toc-title-summary:hover {
  background-color: rgba(0, 0, 0, 0.03);
  color: var(--text-primary);
}

.dark-mode .toc-title-summary:hover {
  background-color: rgba(255, 255, 255, 0.03);
}

.toc-chapter-summary {
  font-family: var(--font-sans);
  font-weight: 500;
  font-size: 0.78rem;
  color: var(--text-secondary);
}

.toc-chapter-summary:hover {
  background-color: rgba(0, 0, 0, 0.03);
  color: var(--text-primary);
}

.dark-mode .toc-chapter-summary:hover {
  background-color: rgba(255, 255, 255, 0.03);
}

.toc-section-summary {
  font-family: var(--font-sans);
  font-weight: 500;
  font-size: 0.76rem;
  color: var(--text-secondary);
}

.toc-section-summary:hover {
  background-color: rgba(0, 0, 0, 0.03);
  color: var(--text-primary);
}

.dark-mode .toc-section-summary:hover {
  background-color: rgba(255, 255, 255, 0.03);
}

/* Article List Leaf Items */
.toc-article-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.toc-item {
  font-size: 0.78rem;
  padding: 6px 10px;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  color: var(--text-secondary);
  transition: background-color 0.2s, color 0.2s, padding-left 0.2s;
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 2px;
}

.toc-item:hover {
  background-color: rgba(0, 0, 0, 0.03);
  color: var(--text-primary);
  padding-left: 14px;
}

.dark-mode .toc-item:hover {
  background-color: rgba(255, 255, 255, 0.03);
}

.toc-item.active {
  background-color: var(--card-bg);
  color: var(--secondary-accent);
  font-weight: 600;
  box-shadow: var(--box-shadow-sm);
  border-left: 3px solid var(--secondary-accent);
  border-top-left-radius: 0;
  border-bottom-left-radius: 0;
}

.toc-item-badge {
  font-size: 0.62rem;
  background: var(--border-color);
  color: var(--text-secondary);
  padding: 1px 5px;
  border-radius: 10px;
  font-weight: 500;
}

/* ==========================================================================
   CENTER PANEL (Textbook View & Quiz Mode)
   ========================================================================== */
#main-content-area {
  background-color: var(--bg-primary);
  height: 100%;
  overflow: hidden;
  position: relative;
  display: flex;
  flex-direction: column;
}

.content-panel {
  display: flex;
  flex-direction: column;
  height: 100%;
  overflow: hidden;
  animation: fadeIn 0.4s ease;
}

.content-panel.hidden {
  display: none !important;
}

.content-header {
  position: relative;
  z-index: 20;
  padding: 20px 32px 14px 32px;
  border-bottom: 1px solid var(--border-color);
  background-color: var(--bg-primary);
  transition: padding 0.25s ease, box-shadow 0.25s ease;
  will-change: padding, box-shadow;
}

.content-header.scrolled {
  padding: 10px 32px 8px 32px;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.12);
  background-color: var(--bg-primary);
}

.dark-mode .content-header.scrolled {
  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.45);
}

.header-breadcrumbs {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  margin-bottom: 4px;
  transition: all 0.25s ease;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 100%;
}

.content-header.scrolled .header-breadcrumbs {
  font-size: 0.68rem;
  margin-bottom: 2px;
}

#textbook-section-title {
  font-family: var(--font-header);
  font-weight: 800;
  font-size: 1.5rem;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: space-between;
  transition: font-size 0.25s ease, color 0.25s ease;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.content-header.scrolled #textbook-section-title {
  font-size: 1.1rem;
}

.official-badge {
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--color-success);
  background: var(--color-success-bg);
  padding: 4px 10px;
  border-radius: 20px;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.badge-dot {
  width: 6px;
  height: 6px;
  background-color: var(--color-success);
  border-radius: 50%;
  display: inline-block;
  animation: pulse 1.5s infinite;
}

/* Scrollable Textbook Container */
#textbook-scroll-container {
  flex: 1;
  overflow-y: auto;
  padding: 24px 32px 80px 32px;
  scroll-behavior: smooth;
}

#articles-wrapper {
  max-width: 780px;
  margin: 0 auto;
}

/* Structuring headings within scroller */
.scroller-heading {
  font-family: var(--font-header);
  color: var(--secondary-accent);
  margin-top: 40px;
  margin-bottom: 16px;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 8px;
}

.scroller-heading.book {
  font-size: 1.3rem;
  font-weight: 800;
  text-transform: uppercase;
  color: var(--text-primary);
}

.scroller-heading.title {
  font-size: 1.15rem;
  font-weight: 700;
}

.scroller-heading.chapter {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--text-secondary);
}

.scroller-heading.section {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-muted);
}

/* Article Card Box */
.article-card {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 20px;
  margin-bottom: 20px;
  box-shadow: var(--box-shadow-sm);
  transition: transform 0.2s, border-color 0.2s, box-shadow 0.2s, background-color 0.2s;
  cursor: pointer;
  position: relative;
}

.article-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--box-shadow-md);
  border-color: var(--secondary-accent);
}

.article-card.active {
  background-color: var(--active-article-bg);
  border-color: var(--active-article-border);
  box-shadow: var(--box-shadow-md);
}

.article-card-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.article-number {
  font-family: var(--font-header);
  font-weight: 700;
  font-size: 1rem;
  color: var(--secondary-accent);
}

.article-meta-actions {
  display: flex;
  gap: 8px;
  align-items: center;
}

/* Bookmark & AI Indicators */
.bookmark-toggle-btn {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  transition: color 0.2s, transform 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 4px;
  border-radius: 4px;
}

.bookmark-toggle-btn:hover {
  color: var(--secondary-accent);
  transform: scale(1.1);
  background: rgba(0,0,0,0.03);
}

.dark-mode .bookmark-toggle-btn:hover {
  background: rgba(255,255,255,0.03);
}

.article-card.bookmarked .bookmark-toggle-btn {
  color: var(--secondary-accent);
}

.article-card.bookmarked .bookmark-toggle-btn svg {
  fill: var(--secondary-accent);
}

.ai-indicator-badge {
  font-size: 0.65rem;
  font-weight: 700;
  background-color: rgba(var(--primary-accent-rgb), 0.1);
  color: var(--primary-accent);
  padding: 2px 8px;
  border-radius: 12px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.read-tick-badge {
  background: none;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  transition: color 0.2s;
  display: flex;
  align-items: center;
}

.read-tick-badge:hover {
  color: var(--color-success);
}

.article-card.read .read-tick-badge {
  color: var(--color-success);
}

/* Article Body Text */
.article-body-text {
  font-family: var(--font-serif);
  font-size: 1rem;
  line-height: 1.65;
  color: var(--text-primary);
}

.article-body-text p {
  margin-bottom: 12px;
}

.article-body-text p:last-child {
  margin-bottom: 0;
}

.article-history {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-family: var(--font-sans);
  margin-top: 12px;
  font-style: italic;
}

/* ==========================================================================
   RIGHT SIDEBAR (AI Study Center)
   ========================================================================== */
#sidebar-right {
  background-color: var(--bg-sidebar-right);
  border-left: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  height: 100%;
  overflow: hidden;
}

.sidebar-right-header {
  padding: 24px 24px 16px 24px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.sidebar-right-header h2 {
  font-family: var(--font-header);
  font-weight: 700;
  font-size: 1.15rem;
}

.ai-pill {
  font-size: 0.65rem;
  font-weight: 700;
  color: var(--secondary-accent);
  background: rgba(var(--secondary-accent-rgb), 0.15);
  border: 1px solid rgba(var(--secondary-accent-rgb), 0.3);
  padding: 3px 8px;
  border-radius: 12px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.sidebar-right-scroll-container {
  flex: 1;
  overflow-y: auto;
  padding: 20px;
}

.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 60%;
  text-align: center;
  color: var(--text-muted);
  padding: 20px;
}

.empty-state svg {
  margin-bottom: 16px;
  color: var(--text-muted);
  opacity: 0.6;
}

.empty-state p {
  font-size: 0.85rem;
  max-width: 240px;
  line-height: 1.5;
}

/* Study Center Cards */
.study-card {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 16px;
  margin-bottom: 16px;
  box-shadow: var(--box-shadow-sm);
  transition: transform 0.2s;
  animation: slideUp 0.3s ease;
}

.study-card h3 {
  font-family: var(--font-header);
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-secondary);
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.study-card p {
  font-size: 0.85rem;
  line-height: 1.5;
  color: var(--text-primary);
}

.study-card.active-article-header-card {
  background: var(--primary-accent);
  border-color: var(--primary-accent);
  color: #FFFFFF;
}

.study-card.active-article-header-card .active-art-label {
  font-family: var(--font-header);
  font-weight: 800;
  font-size: 1.15rem;
}

.study-card.active-article-header-card .active-art-title {
  font-size: 0.75rem;
  color: rgba(255, 255, 255, 0.7);
  margin-top: 2px;
}

/* Exam Alert Card */
.study-card.alert-card {
  border: 1px solid transparent;
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 16px;
}

.study-card.alert-card.high {
  background-color: var(--color-danger-bg);
  border-color: rgba(198, 40, 40, 0.2);
  color: var(--color-danger);
}

.study-card.alert-card.medium {
  background-color: var(--color-warning-bg);
  border-color: rgba(239, 108, 0, 0.2);
  color: var(--color-warning);
}

.study-card.alert-card.low {
  background-color: var(--color-info-bg);
  border-color: rgba(21, 101, 192, 0.2);
  color: var(--color-info);
}

.alert-header {
  font-family: var(--font-header);
  font-size: 0.75rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 8px;
}

/* Accent Card (Relevance) */
.study-card.accent-card {
  border-left: 4px solid var(--secondary-accent);
  background-color: rgba(var(--secondary-accent-rgb), 0.03);
}

/* Scenario Card */
.study-card.scenario-card {
  border: 1px dashed var(--secondary-accent);
  background: var(--card-bg-glass);
}

.scenario-title-row {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--secondary-accent);
  margin-bottom: 8px;
}

.scenario-title-row h3 {
  margin-bottom: 0;
  color: var(--secondary-accent);
}

.study-card.scenario-card p {
  font-style: italic;
  color: var(--text-secondary);
}

/* Definitions List and Items styling */
.definition-item {
  margin-bottom: 16px;
  border-bottom: 1px dashed var(--border-color);
  padding-bottom: 12px;
}

.definition-item:last-child {
  border-bottom: none;
  margin-bottom: 0;
  padding-bottom: 0;
}

.definition-header {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: baseline;
  margin-bottom: 6px;
}

.definition-term {
  font-size: 15px;
  color: var(--primary-accent);
  font-family: var(--font-header);
  font-weight: 700;
}

.definition-phonetic {
  font-size: 12px;
  color: var(--text-muted);
  font-style: italic;
}

.definition-origin {
  font-size: 11px;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  padding: 2px 6px;
  border-radius: 4px;
  color: var(--text-secondary);
  font-weight: 500;
}

.definition-text {
  font-size: 13.5px;
  line-height: 1.45;
  margin: 6px 0;
  color: var(--text-primary);
}

.definition-example {
  font-size: 12.5px;
  font-style: italic;
  background-color: rgba(var(--primary-accent-rgb), 0.04);
  border-left: 3px solid var(--primary-accent);
  padding: 6px 10px;
  margin-top: 6px;
  color: var(--text-secondary);
  border-radius: 0 var(--border-radius-sm) var(--border-radius-sm) 0;
}

.definition-example strong {
  color: var(--text-primary);
}

/* Notes Textarea Card */
.study-card.notes-card {
  background-color: var(--card-bg);
}

.study-card.notes-card textarea {
  width: 100%;
  min-height: 120px;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  padding: 10px;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  color: var(--text-primary);
  resize: vertical;
  outline: none;
  margin-top: 8px;
  transition: border-color 0.2s;
}

.study-card.notes-card textarea:focus {
  border-color: var(--secondary-accent);
}

.notes-status {
  font-size: 0.7rem;
  color: var(--text-muted);
  text-align: right;
  margin-top: 4px;
}

/* ==========================================================================
   QUIZ MODE INTERFACE
   ========================================================================== */
.quiz-badge {
  font-size: 0.7rem;
  font-weight: 700;
  background-color: rgba(var(--primary-accent-rgb), 0.15);
  color: var(--primary-accent);
  padding: 4px 10px;
  border-radius: 20px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  display: inline-block;
  margin-bottom: 4px;
}

.quiz-container {
  max-width: 680px;
  margin: 0 auto;
  padding: 32px 20px 80px 20px;
  flex: 1;
  overflow-y: auto;
  width: 100%;
}

/* Stats Header */
.quiz-dashboard {
  display: flex;
  gap: 16px;
  margin-bottom: 24px;
}

.quiz-card-stat {
  flex: 1;
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 16px;
  text-align: center;
  box-shadow: var(--box-shadow-sm);
}

.quiz-card-stat .stat-number {
  font-family: var(--font-header);
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--secondary-accent);
  display: block;
}

.quiz-card-stat .stat-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  font-weight: 600;
  letter-spacing: 0.5px;
}

/* Question Box */
.question-card {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 24px;
  box-shadow: var(--box-shadow-md);
  margin-bottom: 24px;
}

.question-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.75rem;
  color: var(--text-muted);
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 12px;
  margin-bottom: 16px;
}

.question-number-tag {
  font-weight: 700;
  text-transform: uppercase;
  color: var(--primary-accent);
}

.question-link {
  color: var(--secondary-accent);
  font-weight: 600;
  cursor: pointer;
  text-decoration: underline;
}

.question-text {
  font-family: var(--font-sans);
  font-weight: 600;
  font-size: 1.1rem;
  line-height: 1.5;
  color: var(--text-primary);
  margin-bottom: 24px;
}

/* Options Container */
.options-container {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 20px;
}

.quiz-option-btn {
  width: 100%;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  padding: 14px 18px;
  text-align: left;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  color: var(--text-primary);
  cursor: pointer;
  transition: transform 0.15s, border-color 0.15s, background-color 0.15s;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.quiz-option-btn:hover:not(:disabled) {
  transform: translateX(4px);
  border-color: var(--secondary-accent);
  background-color: var(--card-bg);
}

.quiz-option-btn:disabled {
  cursor: not-allowed;
}

.quiz-option-btn.selected {
  border-color: var(--primary-accent);
  background-color: rgba(var(--primary-accent-rgb), 0.05);
  font-weight: 600;
}

/* Correct / Incorrect Option Classes */
.quiz-option-btn.correct {
  background-color: var(--color-success-bg) !important;
  border-color: var(--color-success) !important;
  color: var(--color-success) !important;
  font-weight: 600;
}

.quiz-option-btn.incorrect {
  background-color: var(--color-danger-bg) !important;
  border-color: var(--color-danger) !important;
  color: var(--color-danger) !important;
}

/* Explanation Panel */
.explanation-box {
  border-top: 1px solid var(--border-color);
  margin-top: 24px;
  padding-top: 20px;
  animation: slideUp 0.3s ease;
}

.explanation-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 8px;
}

.result-badge {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  padding: 3px 8px;
  border-radius: 4px;
}

.result-badge.correct {
  background-color: var(--color-success-bg);
  color: var(--color-success);
}

.result-badge.incorrect {
  background-color: var(--color-danger-bg);
  color: var(--color-danger);
}

.ref-title {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
}

.explanation-body {
  font-size: 0.85rem;
  line-height: 1.5;
  color: var(--text-secondary);
  margin-bottom: 12px;
}

/* Bottom Controls */
.quiz-controls {
  display: flex;
  justify-content: space-between;
  gap: 16px;
}

/* Classic Button Utilities */
.classic-btn {
  background-color: var(--secondary-accent);
  color: #FFFFFF;
  border: none;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  font-weight: 600;
  padding: 10px 20px;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  box-shadow: var(--box-shadow-sm);
  transition: background-color 0.2s, transform 0.15s, opacity 0.2s;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}

.classic-btn:hover {
  background-color: #AF881C;
  transform: translateY(-1px);
}

.classic-btn:active {
  transform: translateY(1px);
}

.classic-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none !important;
}

.classic-btn.secondary {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
}

.classic-btn.secondary:hover {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  border-color: var(--text-secondary);
}

.classic-btn.small {
  padding: 6px 12px;
  font-size: 0.75rem;
}

/* ==========================================================================
   GENERIC OVERLAY AND UTILITIES
   ========================================================================== */
.overlay {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--bg-primary);
  z-index: 100;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 16px;
}

.overlay.hidden {
  display: none !important;
}

.spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--border-color);
  border-top-color: var(--secondary-accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

.icon-btn {
  background: none;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 6px;
  border-radius: 50%;
  transition: background-color 0.2s, color 0.2s;
}

.icon-btn:hover {
  background-color: var(--border-color);
  color: var(--text-primary);
}

/* Toggle Sun/Moon display */
.sun-icon { display: block; }
.moon-icon { display: none; }

.dark-mode .sun-icon { display: none; }
.dark-mode .moon-icon { display: block; }

/* Custom Scrollbars */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

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

::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

/* Highlight search matches */
mark.search-match {
  background-color: rgba(var(--secondary-accent-rgb), 0.25);
  color: inherit;
  border-bottom: 2px solid var(--secondary-accent);
  border-radius: 2px;
}

/* ==========================================================================
   ANIMATIONS
   ========================================================================== */
@keyframes spin {
  to { transform: rotate(360deg); }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

@keyframes slideUp {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes pulse {
  0% { transform: scale(0.95); opacity: 0.7; }
  50% { transform: scale(1.05); opacity: 1; }
  100% { transform: scale(0.95); opacity: 0.7; }
}

/* ==========================================================================
   AI KEY SETTINGS & TUTOR CHAT UPGRADES
   ========================================================================== */
.key-settings-panel {
  background-color: var(--card-bg);
  border-bottom: 1px solid var(--border-color);
  padding: 0 20px;
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition-speed) ease, padding var(--transition-speed) ease;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.key-settings-panel.expanded {
  max-height: 160px;
  padding: 16px 20px;
}

.key-settings-panel label {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--text-secondary);
  letter-spacing: 0.5px;
}

.key-input-row {
  display: flex;
  gap: 8px;
}

.key-input-row input {
  flex: 1;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  padding: 8px 12px;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  color: var(--text-primary);
  outline: none;
}

.key-input-row input:focus {
  border-color: var(--secondary-accent);
}

.key-help-text {
  font-size: 0.7rem;
  color: var(--text-muted);
  line-height: 1.4;
}

.key-help-text a {
  color: var(--secondary-accent);
  text-decoration: underline;
}

/* Generator card */
.study-card.generator-card {
  background: linear-gradient(135deg, rgba(var(--secondary-accent-rgb), 0.05) 0%, rgba(var(--primary-accent-rgb), 0.05) 100%);
  border: 1px solid rgba(var(--secondary-accent-rgb), 0.25);
  box-shadow: 0 4px 12px rgba(var(--secondary-accent-rgb), 0.05);
}

.generator-header {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--secondary-accent);
  margin-bottom: 8px;
}

.sparkle-icon {
  font-size: 1.1rem;
  animation: pulse 2s infinite;
}

/* Chat card */
.study-card.chat-card {
  background-color: var(--card-bg);
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.chat-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 8px;
}

.chat-header h3 {
  margin-bottom: 0;
  font-size: 0.85rem;
  color: var(--text-primary);
}

.chat-thread {
  max-height: 220px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 4px;
}

.chat-message {
  max-width: 85%;
  padding: 10px 14px;
  border-radius: var(--border-radius-md);
  font-size: 0.8rem;
  line-height: 1.4;
  animation: slideUp 0.2s ease;
}

.chat-message p {
  margin-bottom: 0;
}

.chat-message.bot {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  border-bottom-left-radius: 2px;
  border: 1px solid var(--border-color);
  align-self: flex-start;
}

.chat-message.user {
  background-color: var(--primary-accent);
  color: #FFFFFF;
  border-bottom-right-radius: 2px;
  align-self: flex-end;
}

.chat-message.system {
  background-color: rgba(var(--secondary-accent-rgb), 0.15);
  color: var(--secondary-accent);
  align-self: center;
  max-width: 100%;
  font-size: 0.75rem;
  font-style: italic;
  text-align: center;
  border-radius: var(--border-radius-sm);
  padding: 6px 12px;
}

.chat-input-area {
  display: flex;
  gap: 8px;
  border-top: 1px solid var(--border-color);
  padding-top: 8px;
}

.chat-input-area input {
  flex: 1;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  padding: 8px 12px;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  color: var(--text-primary);
  outline: none;
}

.chat-input-area input:focus {
  border-color: var(--secondary-accent);
}

#chat-send-btn {
  background-color: var(--primary-accent);
  color: #FFFFFF;
  border: none;
  border-radius: var(--border-radius-sm);
  padding: 8px 12px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background-color 0.2s, transform 0.1s;
}

#chat-send-btn:hover {
  opacity: 0.9;
  transform: scale(1.05);
}

#chat-send-btn:active {
  transform: scale(0.95);
}

/* Chat bubble loading animation */
.chat-loading-dots {
  display: inline-flex;
  gap: 4px;
  align-items: center;
  height: 12px;
}

.chat-loading-dots span {
  width: 6px;
  height: 6px;
  background-color: var(--text-secondary);
  border-radius: 50%;
  display: inline-block;
  animation: bounce 1.4s infinite ease-in-out both;
}

.chat-loading-dots span:nth-child(1) { animation-delay: -0.32s; }
.chat-loading-dots span:nth-child(2) { animation-delay: -0.16s; }

@keyframes bounce {
  0%, 80%, 100% { transform: scale(0); }
  40% { transform: scale(1.0); }
}

/* Global utility class for hiding elements */
.hidden {
  display: none !important;
}

/* ==========================================================================
   SAAS MVP & AUTHENTICATION STYLES
   ========================================================================== */
#auth-overlay {
  background-color: rgba(15, 20, 28, 0.85);
  backdrop-filter: blur(8px);
  z-index: 9999;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  overflow-y: auto;
}

.auth-card {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-lg);
  box-shadow: var(--box-shadow-lg);
  padding: 36px;
  width: 100%;
  max-width: 480px;
  display: flex;
  flex-direction: column;
  gap: 20px;
  animation: slideUp 0.4s ease;
}

.auth-logo-area {
  font-family: var(--font-header);
  font-weight: 800;
  font-size: 1.4rem;
  letter-spacing: -0.5px;
  text-align: center;
  color: var(--text-primary);
}

.auth-tagline {
  font-size: 0.9rem;
  color: var(--text-secondary);
  text-align: center;
  line-height: 1.5;
  margin-top: -8px;
}

.auth-tabs {
  display: flex;
  border-bottom: 2px solid var(--border-color);
  margin-bottom: 10px;
}

.auth-tab-btn {
  flex: 1;
  background: none;
  border: none;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-secondary);
  padding: 10px;
  cursor: pointer;
  transition: color var(--transition-speed), border-color var(--transition-speed);
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
}

.auth-tab-btn.active {
  color: var(--secondary-accent);
  border-bottom-color: var(--secondary-accent);
}

.auth-form {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.form-group label {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--text-secondary);
  letter-spacing: 0.5px;
}

.form-group input[type="email"],
.form-group input[type="password"] {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  padding: 10px 14px;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  color: var(--text-primary);
  outline: none;
  transition: border-color var(--transition-speed);
}

.form-group input:focus {
  border-color: var(--secondary-accent);
}

.checkbox-group {
  flex-direction: row;
  align-items: center;
  gap: 8px;
}

.checkbox-group input {
  width: 16px;
  height: 16px;
  cursor: pointer;
}

.checkbox-group label {
  text-transform: none;
  font-weight: 500;
  font-size: 0.8rem;
  cursor: pointer;
}

.auth-submit-btn {
  width: 100%;
  padding: 12px;
  font-weight: 600;
  margin-top: 8px;
}

.auth-error-msg {
  background-color: var(--color-danger-bg);
  border: 1px solid rgba(198, 40, 40, 0.2);
  color: var(--color-danger);
  padding: 10px 14px;
  border-radius: var(--border-radius-sm);
  font-size: 0.8rem;
  font-weight: 500;
  line-height: 1.4;
}

.auth-disclaimer-footer {
  border-top: 1px solid var(--border-color);
  padding-top: 16px;
  font-size: 0.7rem;
  color: var(--text-muted);
  line-height: 1.5;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.sidebar-footer {
  padding: 16px 20px;
  border-top: 1px solid var(--border-color);
  margin-top: auto;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.legal-badge-group {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.legal-badge {
  font-size: 0.65rem;
  font-weight: 600;
  color: var(--text-secondary);
  background-color: var(--border-color);
  padding: 2px 6px;
  border-radius: 4px;
}

.sidebar-footer-text {
  font-size: 0.65rem;
  color: var(--text-muted);
  line-height: 1.4;
}

.chat-legal-badge {
  font-size: 0.65rem;
  color: var(--text-muted);
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  padding: 6px 10px;
  margin: -4px 0 4px 0;
  line-height: 1.3;
}

/* Settings View Layout */
.settings-container {
  max-width: 780px;
  margin: 0 auto;
  padding: 24px 32px;
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 24px;
  overflow-y: auto;
}

.settings-card {
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 24px;
  box-shadow: var(--box-shadow-sm);
}

.settings-card h3 {
  font-family: var(--font-header);
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 16px;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 8px;
}

.profile-info-row {
  display: flex;
  justify-content: space-between;
  padding: 10px 0;
  border-bottom: 1px dashed var(--border-color);
  font-size: 0.9rem;
}

.profile-info-row:last-of-type {
  border-bottom: none;
}

.info-label {
  font-weight: 600;
  color: var(--text-secondary);
}

.info-value {
  color: var(--text-primary);
}

.info-value.badge-active {
  background-color: var(--color-success-bg);
  color: var(--color-success);
  font-weight: 700;
  font-size: 0.75rem;
  padding: 2px 8px;
  border-radius: 12px;
  text-transform: uppercase;
}

.disclosure-block {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.disclosure-block p {
  font-size: 0.85rem;
  line-height: 1.6;
  color: var(--text-secondary);
}

.disclosure-block strong {
  color: var(--text-primary);
}

/* Classic Button override for danger */
.classic-btn.danger {
  background-color: var(--color-danger-bg);
  color: var(--color-danger);
  border-color: rgba(198, 40, 40, 0.2);
}

.classic-btn.danger:hover {
  background-color: var(--color-danger);
  color: #FFFFFF;
}

/* ==========================================================================
   INTRODUCTORY GROUNDING CARD (Center Textbook Panel)
   ========================================================================== */
.intro-card {
  background: rgba(var(--secondary-accent-rgb), 0.04);
  border: 1px solid rgba(var(--secondary-accent-rgb), 0.25);
  border-radius: var(--border-radius-md);
  margin-bottom: 24px;
  overflow: hidden;
  box-shadow: var(--box-shadow-sm);
  transition: all var(--transition-speed) ease;
}

.dark-mode .intro-card {
  background: rgba(var(--secondary-accent-rgb), 0.06);
  border: 1px solid rgba(var(--secondary-accent-rgb), 0.35);
}

.intro-card-header {
  padding: 18px 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  user-select: none;
  background-color: rgba(var(--secondary-accent-rgb), 0.02);
  border-bottom: 1px solid rgba(var(--secondary-accent-rgb), 0.15);
  transition: background-color 0.2s;
}

.intro-card-header:hover {
  background-color: rgba(var(--secondary-accent-rgb), 0.06);
}

.intro-header-title {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.intro-badge {
  font-size: 0.65rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--secondary-accent);
  background: rgba(var(--secondary-accent-rgb), 0.12);
  padding: 2px 8px;
  border-radius: 20px;
  width: max-content;
  letter-spacing: 0.5px;
}

.intro-card-header h3 {
  font-family: var(--font-header);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text-primary);
  margin: 0;
}

.intro-chevron {
  color: var(--secondary-accent);
  transition: transform var(--transition-speed) ease;
}

/* Expand / Collapse Transitions */
.intro-card.collapsed .intro-chevron {
  transform: rotate(-90deg);
}

.intro-card.expanded .intro-chevron {
  transform: rotate(0deg);
}

.intro-card-body {
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  transition: max-height 0.3s ease, padding 0.3s ease;
  max-height: 1200px;
  opacity: 1;
}

.intro-card.collapsed .intro-card-body {
  max-height: 0;
  padding-top: 0;
  padding-bottom: 0;
  opacity: 0;
  overflow: hidden;
  border: none;
}

.intro-lead {
  font-family: var(--font-sans);
  font-size: 0.9rem;
  line-height: 1.6;
  color: var(--text-primary);
}

.intro-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

@media (max-width: 768px) {
  .intro-grid {
    grid-template-columns: 1fr;
  }
}

.intro-section {
  display: flex;
  flex-direction: column;
  gap: 8px;
  font-size: 0.85rem;
  line-height: 1.5;
  color: var(--text-secondary);
}

.intro-section h4 {
  font-family: var(--font-header);
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 6px;
}

.intro-section h4 svg {
  color: var(--secondary-accent);
}

.intro-section ul {
  padding-left: 18px;
}

.intro-section li {
  margin-bottom: 6px;
}

.intro-divider {
  height: 1px;
  background-color: rgba(var(--secondary-accent-rgb), 0.15);
  margin: 8px 0;
}

.intro-section.highlight {
  background-color: rgba(var(--primary-accent-rgb), 0.03);
  border: 1px dashed var(--border-color);
  padding: 14px;
  border-radius: var(--border-radius-sm);
}

.dark-mode .intro-section.highlight {
  background-color: rgba(255, 255, 255, 0.02);
}

/* ==========================================================================
   FLOATING FEEDBACK WIDGET
   ========================================================================== */
#feedback-widget {
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 1000;
  font-family: var(--font-sans);
}

#feedback-trigger-btn {
  background-color: var(--primary-accent);
  color: #FFFFFF;
  border: 1px solid var(--border-color);
  padding: 8px 14px;
  border-radius: 30px;
  cursor: pointer;
  box-shadow: var(--box-shadow-md);
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.78rem;
  font-weight: 600;
  transition: all 0.2s ease;
}

.dark-mode #feedback-trigger-btn {
  background-color: var(--secondary-accent);
  color: var(--bg-primary);
  border-color: rgba(255, 255, 255, 0.1);
}

#feedback-trigger-btn:hover {
  transform: translateY(-2px);
  box-shadow: var(--box-shadow-lg);
}

#feedback-trigger-btn:active {
  transform: translateY(0);
}

#feedback-popover {
  position: absolute;
  bottom: 45px;
  right: 0;
  width: 300px;
  background-color: var(--card-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  box-shadow: var(--box-shadow-lg);
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  animation: slideUp 0.2s ease;
}

#feedback-popover.hidden {
  display: none !important;
}

.feedback-popover-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 8px;
}

.feedback-popover-header h4 {
  font-family: var(--font-header);
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--text-primary);
  margin: 0;
}

#feedback-close-btn {
  background: none;
  border: none;
  font-size: 1.2rem;
  color: var(--text-secondary);
  cursor: pointer;
  transition: color 0.2s;
  line-height: 1;
}

#feedback-close-btn:hover {
  color: var(--text-primary);
}

#feedback-form {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

#feedback-form .form-group {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

#feedback-form label {
  font-size: 0.68rem;
  font-weight: 600;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

#feedback-form select,
#feedback-form input[type="email"],
#feedback-form textarea,
#feedback-form input[type="file"] {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 0.78rem;
  padding: 6px 10px;
  border-radius: var(--border-radius-sm);
  outline: none;
  width: 100%;
}

#feedback-form select:focus,
#feedback-form input[type="email"]:focus,
#feedback-form textarea:focus {
  border-color: var(--secondary-accent);
}

#feedback-form textarea {
  resize: vertical;
}

#feedback-form input[type="file"] {
  font-size: 0.72rem;
  padding: 4px;
  background: none;
  border: 1px dashed var(--border-color);
  cursor: pointer;
}

.feedback-submit-btn {
  font-size: 0.78rem;
  padding: 8px 12px;
  width: 100%;
  margin-top: 4px;
}

.feedback-success {
  background-color: var(--color-success-bg);
  color: var(--color-success);
  border: 1px solid rgba(76, 175, 80, 0.2);
  padding: 6px 10px;
  border-radius: var(--border-radius-sm);
  font-size: 0.72rem;
  font-weight: 600;
  text-align: center;
}

.feedback-error {
  background-color: var(--color-danger-bg);
  color: var(--color-danger);
  border: 1px solid rgba(244, 67, 54, 0.2);
  padding: 6px 10px;
  border-radius: var(--border-radius-sm);
  font-size: 0.72rem;
  font-weight: 600;
  text-align: center;
}