/* ==========================================
   1. TOKENS & DESIGN SYSTEM (DUOLINGO STYLE)
   ========================================== */
:root {
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --border-color: #e2e8f0;
  
  --accent-color: #3b82f6;
  --accent-hover: #2563eb;
  --accent-shadow: #1d4ed8;
  --accent-bg-alpha: rgba(59, 130, 246, 0.08);
  
  --success-color: #22c55e;
  --success-bg: #f0fdf4;
  --success-shadow: #15803d;
  --success-border: #86efac;
  
  --error-color: #ef4444;
  --error-bg: #fef2f2;
  --error-shadow: #b91c1c;
  --error-border: #fca5a5;
  
  --warn-color: #f59e0b;
  --warn-bg: #fffbeb;
  
  --card-shadow: 0 8px 16px -4px rgba(0, 0, 0, 0.04);
  --sidebar-width: 280px;
  --transition-speed: 0.15s;
  --font-family: 'Inter', system-ui, -apple-system, sans-serif;
  --border-radius-sm: 0.5rem;
  --border-radius-md: 0.75rem;
  --border-radius-lg: 1rem;
}

[data-theme="dark"] {
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --border-color: #334155;
  
  --accent-color: #60a5fa;
  --accent-hover: #3b82f6;
  --accent-shadow: #1d4ed8;
  --accent-bg-alpha: rgba(96, 165, 250, 0.15);
  
  --success-color: #4ade80;
  --success-bg: #064e3b;
  --success-shadow: #15803d;
  --success-border: #047857;
  
  --error-color: #f87171;
  --error-bg: #7f1d1d;
  --error-shadow: #b91c1c;
  --error-border: #991b1b;
  
  --warn-color: #fbbf24;
  --warn-bg: #78350f;
}

/* ==========================================
   2. BASE RESETS & KEYBOARD ACCESS
   ========================================== */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: var(--font-family);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  display: flex;
  height: 100vh;
  overflow: hidden;
}

button:focus-visible, 
input:focus-visible, 
select:focus-visible, 
textarea:focus-visible,
[role="button"]:focus-visible {
  outline: 2px solid var(--accent-color);
  outline-offset: 2px;
}

.duo-btn, 
.tab-btn, 
.option-item, 
.grid-btn, 
.chapter-progress-card, 
.filter-select, 
.search-input,
.vocab-mode-btn,
.match-card {
  transition: background-color var(--transition-speed) ease, 
              border-color var(--transition-speed) ease, 
              color var(--transition-speed) ease, 
              transform var(--transition-speed) ease, 
              box-shadow var(--transition-speed) ease;
}

/* ==========================================
   3. LAYOUT & VIEWPORTS
   ========================================== */
.app-container {
  display: flex;
  width: 100%;
  height: 100%;
}

.main-content {
  flex: 1;
  display: flex;
  flex-direction: column;
  height: 100%;
  overflow-y: auto;
  background-color: var(--bg-primary);
  position: relative;
}

.content-area {
  flex: 1;
  padding: 2rem;
  max-width: 900px;
  width: 100%;
  margin: 0 auto;
}

.content-area.expanded {
  max-width: 1200px;
}

.sidebar-backdrop {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  background: rgba(15, 23, 42, 0.4);
  backdrop-filter: blur(4px);
  z-index: 99;
}

/* ==========================================
   4. SIDEBAR PANEL (280px)
   ========================================== */
.sidebar {
  width: var(--sidebar-width);
  background-color: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  height: 100%;
  flex-shrink: 0;
  z-index: 100;
  transition: width var(--transition-speed) ease, opacity var(--transition-speed) ease, border-color var(--transition-speed) ease;
}
.sidebar.sidebar-collapsed {
  width: 0 !important;
  opacity: 0;
  pointer-events: none;
  border-right: none;
}

.sidebar-header {
  padding: 1.25rem;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.sidebar-title {
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--accent-color);
  letter-spacing: -0.5px;
}

.theme-toggle-btn {
  background: none;
  border: 2px solid var(--border-color);
  box-shadow: 0 3px 0 var(--border-color);
  color: var(--text-primary);
  padding: 0.5rem;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  font-size: 0.85rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  width: 100%;
  justify-content: center;
  font-weight: 700;
  position: relative;
  top: 0;
}

.theme-toggle-btn:hover {
  background-color: var(--bg-primary);
}

.theme-toggle-btn:active {
  transform: translateY(3px);
  box-shadow: none;
}

.nav-filters {
  padding: 1.25rem 1.25rem 0.5rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.search-input {
  width: 100%;
  padding: 0.55rem 0.75rem;
  border-radius: var(--border-radius-sm);
  border: 2px solid var(--border-color);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-size: 0.85rem;
}

.search-input:focus {
  border-color: var(--accent-color);
  outline: none;
}

.filter-select {
  width: 100%;
  padding: 0.55rem 0.75rem;
  border-radius: var(--border-radius-sm);
  border: 2px solid var(--border-color);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-size: 0.85rem;
  cursor: pointer;
}

.grid-container {
  flex: 1;
  overflow-y: auto;
  padding: 1rem 1.25rem;
}

.nav-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 0.4rem;
}

.grid-btn {
  aspect-ratio: 1;
  border: 2px solid var(--border-color);
  box-shadow: 0 3px 0 var(--border-color);
  border-radius: var(--border-radius-sm);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  font-weight: 700;
  font-size: 0.8rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  top: 0;
}

.grid-btn:hover {
  border-color: var(--accent-color);
  box-shadow: 0 3px 0 var(--accent-color);
}

.grid-btn:active {
  transform: translateY(3px);
  box-shadow: none;
}

.grid-btn.active {
  border-color: var(--accent-color);
  box-shadow: 0 3px 0 var(--accent-color);
  outline: 2px solid var(--accent-color);
  outline-offset: 1px;
}

.grid-btn.answered {
  background-color: var(--border-color);
}

.grid-btn.correct {
  background-color: var(--success-bg);
  color: var(--success-color);
  border-color: var(--success-color);
  box-shadow: 0 3px 0 var(--success-color);
}

.grid-btn.incorrect {
  background-color: var(--error-bg);
  color: var(--error-color);
  border-color: var(--error-color);
  box-shadow: 0 3px 0 var(--error-color);
}

.grid-btn.flagged::after {
  content: '🚩';
  position: absolute;
  top: 0px;
  right: 1px;
  font-size: 0.6rem;
}

/* ==========================================
   5. TOP NAVIGATION BAR
   ========================================== */
.top-navbar {
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem 2rem;
  position: sticky;
  top: 0;
  z-index: 10;
  gap: 1rem;
}

.mobile-hamburger-btn {
  display: inline-flex;
  background: none;
  border: 2px solid var(--border-color);
  box-shadow: 0 3px 0 var(--border-color);
  color: var(--text-primary);
  padding: 0.5rem;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  font-size: 1rem;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  position: relative;
  top: 0;
}

.mobile-hamburger-btn:active {
  transform: translateY(3px);
  box-shadow: none;
}

.mode-tabs {
  display: flex;
  gap: 0.5rem;
}

.tab-btn {
  background: none;
  border: none;
  padding: 0.5rem 0.85rem;
  color: var(--text-secondary);
  font-weight: 700;
  font-size: 0.9rem;
  cursor: pointer;
  border-bottom: 2px solid transparent;
}

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

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

.stats-container {
  display: flex;
  align-items: center;
  gap: 1rem;
  font-size: 0.85rem;
}

.stat-badge {
  display: flex;
  align-items: center;
  gap: 0.3rem;
  font-weight: 700;
}

/* ==========================================
   6. CARDS & MCQS
   ========================================== */
.card {
  background-color: var(--bg-secondary);
  border-radius: var(--border-radius-lg);
  border: 2px solid var(--border-color);
  box-shadow: 0 6px 0 var(--border-color);
  padding: 2rem;
  margin-bottom: 2rem;
  position: relative;
}

.q-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-bottom: 1.25rem;
}

.q-text {
  font-size: 1.2rem;
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 1.5rem;
  line-height: 1.7;
}

.options-list {
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
}

.option-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.9rem 1.25rem;
  border: 2px solid var(--border-color);
  box-shadow: 0 4px 0 var(--border-color);
  border-radius: var(--border-radius-md);
  cursor: pointer;
  font-weight: 700;
  line-height: 1.6;
  text-align: left;
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  position: relative;
  top: 0;
  margin-bottom: 4px;
}

.option-item:hover:not(.disabled):not(.correct):not(.incorrect) {
  border-color: var(--accent-color);
  box-shadow: 0 4px 0 var(--accent-color);
  background-color: var(--accent-bg-alpha);
}

.option-item:active:not(.disabled) {
  transform: translateY(4px);
  box-shadow: none;
}

.option-radio {
  margin-right: 0.75rem;
  flex-shrink: 0;
  width: 18px;
  height: 18px;
}

.option-item-content {
  display: flex;
  align-items: center;
  flex: 1;
}

.option-item.correct {
  background-color: var(--success-bg);
  border-color: var(--success-color);
  box-shadow: 0 4px 0 var(--success-shadow);
}

.option-item.incorrect {
  background-color: var(--error-bg);
  border-color: var(--error-color);
  box-shadow: 0 4px 0 var(--error-shadow);
}

.option-item.selected-temp {
  border-color: var(--accent-color);
  box-shadow: 0 4px 0 var(--accent-color);
  background-color: var(--accent-bg-alpha);
}

.option-item.disabled {
  opacity: 0.7;
  cursor: not-allowed;
  box-shadow: none;
  transform: translateY(4px);
}

.option-badge {
  font-size: 0.7rem;
  font-weight: 800;
  padding: 0.25rem 0.5rem;
  border-radius: var(--border-radius-sm);
  margin-left: 0.75rem;
  white-space: nowrap;
  flex-shrink: 0;
}

.option-badge.success-badge {
  background-color: var(--success-color);
  color: white;
}

.option-badge.error-badge {
  background-color: var(--error-color);
  color: white;
}

.explanation {
  margin-top: 1.5rem;
  padding: 1.25rem;
  border-radius: var(--border-radius-md);
  background-color: var(--bg-primary);
  border-left: 4px solid var(--accent-color);
  font-size: 0.85rem;
}

.explanation-title {
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.explanation-note {
  margin-top: 0.5rem;
  padding-top: 0.5rem;
  border-top: 1px dashed var(--border-color);
  color: var(--text-secondary);
  line-height: 1.5;
}

.quiz-image {
  max-width: 100%;
  height: auto;
  border-radius: var(--border-radius-md);
  border: 2px solid var(--border-color);
  margin: 1rem 0 1.5rem;
  display: block;
}

/* 3D button definitions */
.btn {
  padding: 0.65rem 1.25rem;
  border-radius: var(--border-radius-sm);
  font-weight: 700;
  cursor: pointer;
  font-size: 0.85rem;
  border: 2px solid var(--border-color);
  box-shadow: 0 4px 0 var(--border-color);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  position: relative;
  top: 0;
  margin-bottom: 4px;
}

.btn:hover:not(:disabled) {
  background-color: var(--bg-primary);
}

.btn:active:not(:disabled) {
  transform: translateY(4px);
  box-shadow: none;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  box-shadow: none;
  transform: translateY(4px);
}

.btn-primary {
  background-color: var(--accent-color);
  color: white;
  border-color: var(--accent-hover);
  box-shadow: 0 4px 0 var(--accent-shadow);
}

.btn-primary:hover:not(:disabled) {
  background-color: var(--accent-hover);
}

.btn-primary:active:not(:disabled) {
  box-shadow: none;
}

.btn-danger {
  background-color: var(--error-color);
  color: white;
  border-color: #dc2626;
  box-shadow: 0 4px 0 var(--error-shadow);
}

.btn-danger:hover:not(:disabled) {
  background-color: #dc2626;
}

.btn-danger:active:not(:disabled) {
  box-shadow: none;
}

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

.btn-secondary:hover:not(:disabled) {
  border-color: var(--accent-color);
  color: var(--accent-color);
}

.nav-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 1.5rem;
}

/* ==========================================
   7. RUBY & TOOLTIPS
   ========================================== */
ruby {
  ruby-position: over;
  ruby-align: center;
}

rt {
  font-size: 0.55em;
  color: var(--accent-color);
  user-select: none;
  letter-spacing: 0.5px;
  padding-bottom: 2px;
}

.kanji-tooltip {
  position: relative;
  border-bottom: 1px dashed var(--accent-color);
  cursor: help;
  display: inline-block;
  padding: 0 1px;
}

.kanji-tooltip::after {
  content: attr(data-hanviet);
  position: absolute;
  bottom: 125%;
  left: 50%;
  transform: translateX(-50%) scale(0.9);
  background-color: #1e293b;
  color: #f8fafc;
  padding: 5px 10px;
  border-radius: var(--border-radius-sm);
  font-size: 0.7rem;
  font-weight: bold;
  white-space: nowrap;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.15s ease, transform 0.15s ease;
  box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.3);
  z-index: 10;
  border: 1px solid rgba(255, 255, 255, 0.1);
  letter-spacing: 1px;
}

[data-theme="dark"] .kanji-tooltip::after {
  background-color: #0f172a;
}

.kanji-tooltip:hover::after {
  opacity: 1;
  transform: translateX(-50%) scale(1);
}

/* ==========================================
   8. VOCABULARY VIEW
   ========================================== */
.vocab-modes-switch {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
  justify-content: center;
}

.vocab-mode-btn {
  padding: 0.5rem 1.15rem;
  border-radius: 20px;
  background-color: var(--bg-secondary);
  border: 2px solid var(--border-color);
  box-shadow: 0 3px 0 var(--border-color);
  color: var(--text-secondary);
  cursor: pointer;
  font-weight: 700;
  font-size: 0.85rem;
  position: relative;
  top: 0;
  margin-bottom: 3px;
}

.vocab-mode-btn:hover {
  border-color: var(--accent-color);
  color: var(--text-primary);
  box-shadow: 0 3px 0 var(--accent-color);
}

.vocab-mode-btn:active {
  transform: translateY(3px);
  box-shadow: none;
}

.vocab-mode-btn.active {
  background-color: var(--accent-color);
  color: white;
  border-color: var(--accent-hover);
  box-shadow: 0 3px 0 var(--accent-shadow);
}

.vocab-mode-btn.active:active {
  transform: translateY(3px);
  box-shadow: none;
}

.vocab-table-container {
  background: var(--bg-secondary);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius-lg);
  overflow-x: auto;
  max-height: calc(100vh - 230px);
  overflow-y: auto;
  box-shadow: var(--card-shadow);
}

table.vocab-table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
}

table.vocab-table th {
  background: var(--bg-primary);
  padding: 0.9rem 1rem;
  font-weight: 700;
  color: var(--text-secondary);
  border-bottom: 2px solid var(--border-color);
  font-size: 0.85rem;
  position: sticky;
  top: 0;
  z-index: 2;
}

table.vocab-table td {
  padding: 0.9rem 1rem;
  border-bottom: 1px solid var(--border-color);
  vertical-align: middle;
  font-size: 0.9rem;
}

table.vocab-table tr:hover {
  background: rgba(99, 102, 241, 0.02);
}

/* Col widths in vocab list */
.col-speaker {
  width: 50px;
  text-align: center;
}
.col-word {
  font-size: 1.05rem;
  font-weight: 600;
  min-width: 140px;
}
.col-reading {
  color: var(--accent-color);
  font-weight: 600;
  min-width: 100px;
}
.col-hanviet {
  font-weight: bold;
  min-width: 100px;
}
.col-meaning {
  font-weight: 500;
  min-width: 140px;
}
.col-example {
  font-size: 0.85rem;
  line-height: 1.5;
  max-width: 350px;
}
.col-example-meaning {
  color: var(--text-secondary);
  margin-top: 2px;
}
.vocab-cb-input {
  margin-right: 8px;
  width: 16px;
  height: 16px;
  cursor: pointer;
  vertical-align: middle;
}

/* Flashcard Styles */
.flashcard-wrapper {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.5rem;
  padding: 1rem 0;
}

.flashcard {
  width: 100%;
  max-width: 480px;
  height: 280px;
  perspective: 1000px;
  cursor: pointer;
}

.card-inner {
  width: 100%;
  height: 100%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

.flashcard.flipped .card-inner {
  transform: rotateY(180deg);
}

.card-front, .card-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  background-color: var(--bg-secondary);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius-lg);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  box-shadow: 0 6px 0 var(--border-color);
}

.card-back {
  transform: rotateY(180deg);
  justify-content: space-around;
}

.card-front h2 {
  font-size: 2.25rem;
  font-weight: 800;
  text-align: center;
  line-height: 1.6;
}

.card-back h3 {
  font-size: 1.35rem;
  color: var(--accent-color);
}

.card-back p {
  text-align: center;
}

.flashcard-front-desc {
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-top: 1.5rem;
}
.flashcard-back-header {
  text-align: center;
}
.flashcard-back-reading {
  color: var(--accent-color);
  font-weight: 700;
  margin-top: 4px;
}
.flashcard-back-hanviet {
  font-weight: bold;
  margin-top: 2px;
}
.flashcard-back-content {
  text-align: center;
  padding: 0 0.5rem;
  max-width: 100%;
}
.flashcard-back-meaning {
  font-weight: 600;
  font-size: 1rem;
  margin-bottom: 0.5rem;
}
.flashcard-back-example {
  text-align: left;
  font-size: 0.8rem;
  border-top: 1px dashed var(--border-color);
  padding-top: 0.5rem;
  margin-top: 0.5rem;
  max-height: 100px;
  overflow-y: auto;
}

.btn-speaker {
  background: none;
  border: none;
  cursor: pointer;
  font-size: 1.1rem;
  color: var(--accent-color);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 4px;
  transition: transform 0.1s ease;
  user-select: none;
}
.btn-speaker:active {
  transform: scale(0.85);
}

.flashcard-speak-btn {
  width: 38px;
  height: 38px;
  border-radius: 50% !important;
  background: var(--bg-primary) !important;
  border: 2px solid var(--border-color) !important;
  box-shadow: 0 2px 0 var(--border-color) !important;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}
.flashcard-speak-btn:active {
  transform: translateY(2px) !important;
  box-shadow: none !important;
}


/* ==========================================
   9. INTERACTIVE CARD MATCHING GAME
   ========================================== */
.match-pairs-container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
  margin-top: 1rem;
}

.match-column {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.match-card {
  border: 2px solid var(--border-color);
  box-shadow: 0 4px 0 var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 1rem;
  text-align: center;
  cursor: pointer;
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 70px;
  line-height: 1.4;
  user-select: none;
  position: relative;
  top: 0;
  margin-bottom: 4px;
}

.match-card:hover:not(.matched):not(.selected):not(.correct):not(.incorrect) {
  border-color: var(--accent-color);
  box-shadow: 0 4px 0 var(--accent-color);
}

.match-card:active:not(.matched) {
  transform: translateY(4px);
  box-shadow: none;
}

.match-card.selected {
  border-color: var(--accent-color);
  box-shadow: 0 4px 0 var(--accent-color);
  background-color: var(--accent-bg-alpha);
  outline: 2px solid var(--accent-color);
}

.match-card.correct {
  background-color: var(--success-bg);
  border-color: var(--success-color);
  box-shadow: 0 4px 0 var(--success-shadow);
  color: var(--text-primary);
}

.match-card.incorrect {
  background-color: var(--error-bg);
  border-color: var(--error-color);
  box-shadow: 0 4px 0 var(--error-shadow);
  color: var(--text-primary);
}

.match-card.matched {
  opacity: 0;
  pointer-events: none;
  transform: scale(0.9);
  transition: all 0.3s ease;
}

.match-card.shake {
  animation: shake 0.4s ease;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20%, 60% { transform: translateX(-6px); }
  40%, 80% { transform: translateX(6px); }
}

.game-header {
  display: flex;
  justify-content: space-between;
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: bold;
  border-bottom: 2px solid var(--border-color);
  padding-bottom: 8px;
  margin-bottom: 1.5rem;
}

.game-finish-card {
  text-align: center;
  padding: 3rem 0;
}

.game-finish-title {
  font-size: 1.8rem;
  color: var(--success-color);
  margin-bottom: 1rem;
}

.game-finish-desc {
  font-size: 1.2rem;
  color: var(--text-secondary);
  margin-bottom: 2rem;
}

/* ==========================================
   10. SYSTEM SETTINGS
   ========================================== */
.settings-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.5rem;
  margin-top: 1rem;
}

.settings-section {
  background-color: var(--bg-secondary);
  border: 2px solid var(--border-color);
  box-shadow: 0 4px 0 var(--border-color);
  border-radius: var(--border-radius-lg);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  margin-bottom: 1.5rem;
}

.settings-section h3 {
  font-size: 1.1rem;
  font-weight: 800;
  color: var(--accent-color);
  border-bottom: 2px solid var(--border-color);
  padding-bottom: 6px;
  margin-bottom: 0.5rem;
}

.settings-item {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.settings-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.settings-label {
  font-weight: 700;
  font-size: 0.9rem;
}

.settings-desc {
  font-size: 0.8rem;
  color: var(--text-secondary);
  line-height: 1.4;
}

.settings-slider {
  width: 100%;
  accent-color: var(--accent-color);
  cursor: pointer;
}

.settings-textarea {
  width: 100%;
  min-height: 100px;
  background-color: var(--bg-primary);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 0.75rem;
  color: var(--text-primary);
  font-size: 0.85rem;
  font-family: monospace;
  resize: vertical;
}

.settings-textarea:focus {
  border-color: var(--accent-color);
  outline: none;
}

.settings-row-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.settings-import-export-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

.settings-button-align {
  padding: 2px 8px;
  font-size: 0.75rem;
  margin-bottom: 0;
}

/* Custom Display settings rules */
body.hide-furigana rt {
  display: none !important;
}

body.hide-hanviet .kanji-tooltip {
  border-bottom: none !important;
  cursor: default !important;
}

body.hide-hanviet .kanji-tooltip::after {
  display: none !important;
}

body.hide-furigana-match .match-card rt {
  display: none !important;
}

/* ==========================================
   11. ESSAYS
   ========================================== */
.essay-textarea {
  width: 100%;
  min-height: 140px;
  background-color: var(--bg-primary);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 1rem;
  color: var(--text-primary);
  font-size: 0.95rem;
  line-height: 1.6;
  resize: vertical;
  margin-top: 1rem;
}

.essay-textarea:focus {
  border-color: var(--accent-color);
  outline: none;
}

.essay-feedback-box {
  background-color: var(--bg-primary);
  border: 2px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 1.25rem;
  margin-top: 1.5rem;
  display: none;
}

.essay-feedback-box.active {
  display: block;
}

.self-eval-btns {
  display: flex;
  gap: 0.75rem;
  margin-top: 1.25rem;
}

.btn-eval {
  flex: 1;
  padding: 0.65rem;
  border-radius: var(--border-radius-sm);
  font-weight: 700;
  cursor: pointer;
  border: 2px solid transparent;
  box-shadow: 0 3px 0 transparent;
  font-size: 0.85rem;
  position: relative;
  top: 0;
  margin-bottom: 3px;
}

.btn-eval:active {
  transform: translateY(3px);
  box-shadow: none;
}

.btn-eval.correct {
  background-color: var(--success-bg);
  color: var(--success-color);
  border-color: var(--success-color);
  box-shadow: 0 3px 0 var(--success-color);
}

.btn-eval.incorrect {
  background-color: var(--error-bg);
  color: var(--error-color);
  border-color: var(--error-color);
  box-shadow: 0 3px 0 var(--error-color);
}

.essay-feedback-item {
  margin-bottom: 1.25rem;
}

.essay-feedback-title {
  color: var(--accent-color);
  font-weight: bold;
  font-size: 0.9rem;
  margin-bottom: 4px;
}

.essay-feedback-title.warn {
  color: var(--warn-color);
}

.essay-feedback-content {
  font-size: 1rem;
  padding: 12px;
  background: var(--bg-primary);
  border-radius: var(--border-radius-md);
  border: 1px solid var(--border-color);
  line-height: 1.7;
}

.essay-eval-container {
  border-top: 1px dashed var(--border-color);
  padding-top: 1rem;
  margin-top: 1.5rem;
  text-align: center;
}

.essay-eval-title {
  font-weight: 600;
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
}

/* ==========================================
   12. LEARNING DASHBOARD
   ========================================== */
.dashboard-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.25rem;
  margin-top: 1.5rem;
}

.chapter-progress-card {
  background-color: var(--bg-secondary);
  border: 2px solid var(--border-color);
  box-shadow: 0 4px 0 var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  position: relative;
  top: 0;
  margin-bottom: 4px;
}

.chapter-progress-card:hover {
  border-color: var(--accent-color);
  box-shadow: 0 4px 0 var(--accent-color);
}

.chapter-progress-card:active {
  transform: translateY(4px);
  box-shadow: none;
}

.chapter-progress-card-title {
  font-size: 0.95rem;
  font-weight: 700;
  line-height: 1.4;
}

.progress-bar-container {
  width: 100%;
  height: 8px;
  background: var(--bg-primary);
  border-radius: 4px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent-color), #a855f7);
  width: 0%;
}

.db-card-header {
  font-size: 1.4rem;
  font-weight: 800;
  margin-bottom: 0.75rem;
  color: var(--accent-color);
}

.db-card-desc {
  color: var(--text-secondary);
  margin-bottom: 1.75rem;
  font-size: 0.9rem;
}

.db-metrics-container {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1rem;
  margin-top: 0.5rem;
}

.db-metric-card {
  background: var(--bg-primary);
  padding: 1rem;
  border-radius: var(--border-radius-md);
  border: 2px solid var(--border-color);
}

.db-metric-title {
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.db-metric-value {
  font-size: 1.35rem;
  font-weight: 800;
  margin: 4px 0;
}

.db-section-title {
  font-size: 1.1rem;
  font-weight: 800;
  margin-bottom: 1rem;
  letter-spacing: -0.2px;
}

.hidden {
  display: none !important;
}

/* ==========================================
   13. MOBILE RESPONSIVE
   ========================================== */
@media (max-width: 768px) {
  .mobile-hamburger-btn {
    display: inline-flex;
  }
  
  .sidebar {
    position: fixed;
    top: 0;
    left: 0;
    height: 100%;
    transform: translateX(-100%);
    transition: transform var(--transition-speed) ease;
    z-index: 100;
    box-shadow: 10px 0 15px -3px rgba(0, 0, 0, 0.1);
  }
  
  .sidebar.sidebar-open {
    transform: translateX(0);
  }
  
  .sidebar-backdrop.active {
    display: block;
  }
  
  .top-navbar {
    padding: 0.5rem 1rem;
  }
  
  .mode-tabs {
    overflow-x: auto;
    white-space: nowrap;
    max-width: calc(100vw - 120px);
    padding-bottom: 2px;
  }
  
  .tab-btn {
    padding: 0.4rem 0.6rem;
    font-size: 0.85rem;
  }
  
  .stats-container {
    gap: 0.5rem;
    font-size: 0.75rem;
  }
  
  .stat-badge {
    display: none;
  }
  
  #stat-progress {
    display: inline-flex;
    font-weight: 700;
  }
  
  .content-area {
    padding: 1rem;
  }
  
  .card {
    padding: 1.25rem;
    box-shadow: 0 4px 0 var(--border-color);
  }
  
  .q-text {
    font-size: 1rem;
  }
  
  .option-item {
    padding: 0.75rem 1rem;
    font-size: 0.85rem;
  }
}