/* ==========================================================================
   Decks View Stylesheet - Level 1 Decks, Level 2 Subtopics, Level 3 Words
   Refactored Single-File Architecture (CSS Tokens & Zero Redundancy)
   ========================================================================== */

/* --------------------------------------------------------------------------
   Level 1: Main Decks Overview List & Headers
   -------------------------------------------------------------------------- */
.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
}

.section-title {
  font-size: 1.15rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}

.deck-taxonomy-strip {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-top: 3px;
  font-size: 0.74rem;
  color: var(--text-muted);
  font-weight: 500;
}

.deck-taxonomy-strip strong {
  color: var(--text-primary);
  font-weight: 700;
  font-family: var(--font-mono);
}

.deck-taxonomy-strip .tax-bullet {
  color: var(--border);
  font-size: 0.55rem;
}

/* --------------------------------------------------------------------------
   Level 1: Decks Header Toolbar, Filter Chips & Search
   -------------------------------------------------------------------------- */
.decks-header-bar {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 14px;
}

.decks-filter-chips {
  display: flex;
  gap: 8px;
  overflow-x: auto;
  padding: 2px 2px 6px 2px;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}

.decks-filter-chips::-webkit-scrollbar {
  display: none;
}

.filter-chip {
  padding: 6px 12px;
  border-radius: var(--radius-full);
  font-size: 0.8rem;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  cursor: pointer;
  white-space: nowrap;
  flex-shrink: 0;
  transition: all var(--transition-normal);
  box-shadow: var(--shadow-sm);
}

.filter-chip:hover {
  border-color: var(--primary);
  color: var(--text-primary);
  transform: translateY(-1px);
}

.filter-chip .chip-count {
  font-size: 0.72rem;
  font-weight: 800;
  padding: 1px 6px;
  border-radius: var(--radius-full);
  background: var(--bg-tertiary);
  color: var(--text-muted);
  transition: all var(--transition-fast);
}

.filter-chip.active {
  background: linear-gradient(135deg, var(--primary), #4f46e5);
  border-color: transparent;
  color: #ffffff;
  box-shadow: 0 4px 14px var(--primary-glow);
  transform: translateY(-1px);
}

.filter-chip.active .chip-count {
  background: rgba(255, 255, 255, 0.25);
  color: #ffffff;
}

.decks-sub-toolbar {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 0 2px;
}

.decks-toolbar-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.decks-count-summary {
  font-size: 0.78rem;
  font-weight: 700;
  color: var(--text-muted);
  letter-spacing: -0.01em;
}

.decks-filter-dropdowns {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
  width: 100%;
}

.decks-select-wrap {
  position: relative;
  width: 100%;
}

.decks-select-wrap select {
  width: 100%;
  font-size: 0.8rem;
  font-weight: 600;
  padding: 8px 26px 8px 11px;
  border-radius: var(--radius-md);
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-primary);
  cursor: pointer;
  outline: none;
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%2364748b' stroke-width='2.5' stroke-linecap='round' stroke-linejoin='round'%3E%3Cpath d='m6 9 6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 10px center;
  text-overflow: ellipsis;
  white-space: nowrap;
  overflow: hidden;
  transition: all var(--transition-normal);
  box-shadow: var(--shadow-sm);
}

.decks-select-wrap select:hover,
.decks-select-wrap select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-glow);
}

/* --------------------------------------------------------------------------
   Level 1: Deck Item Cards
   -------------------------------------------------------------------------- */
.decks-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.deck-item-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  gap: 12px;
  cursor: pointer;
  transition: all 0.22s cubic-bezier(0.34, 1.56, 0.64, 1);
  position: relative;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.deck-item-card.deck-item-recent {
  border-color: rgba(245, 158, 11, 0.45);
  box-shadow: 0 4px 18px rgba(245, 158, 11, 0.08);
}

.deck-item-card.deck-item-pinned {
  border-color: rgba(99, 102, 241, 0.5);
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.06) 0%, var(--bg-card) 100%);
  box-shadow: 0 4px 20px var(--primary-glow);
}

.deck-item-card:hover {
  border-color: var(--primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

/* Header Row: Icon + Full Titles + Pin */
.deck-card-header {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  position: relative;
  width: 100%;
}

.deck-icon-badge {
  width: 46px;
  height: 46px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.45rem;
  flex-shrink: 0;
  background: var(--bg-tertiary);
  transition: transform 0.25s cubic-bezier(0.34, 1.56, 0.64, 1);
  margin-top: 1px;
  box-shadow: var(--shadow-sm);
}

.deck-item-card:hover .deck-icon-badge {
  transform: scale(1.1) rotate(4deg);
}

.deck-info {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 3px;
  padding-right: 28px;
}

.deck-title {
  font-size: 1.05rem;
  font-weight: 800;
  color: var(--text-primary);
  line-height: 1.35;
  letter-spacing: -0.015em;
  word-break: break-word;
}

.deck-sub-title {
  font-size: 0.82rem;
  color: var(--text-secondary);
  font-weight: 500;
  line-height: 1.35;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.btn-deck-pin {
  position: absolute;
  top: -4px;
  right: -4px;
  width: 28px;
  height: 28px;
  background: transparent;
  border: none;
  border-radius: var(--radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
  transition: all var(--transition-normal);
  opacity: 0.45;
  font-size: 0.95rem;
}

.btn-deck-pin:hover {
  background: var(--bg-tertiary);
  color: var(--primary);
  opacity: 1;
  transform: scale(1.15);
}

.btn-deck-pin.pinned {
  color: #f59e0b;
  opacity: 1;
  transform: rotate(-15deg);
}

/* Footer Row: Metadata + Actions */
.deck-card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  margin-top: 2px;
}

.deck-meta-strip {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.78rem;
  color: var(--text-muted);
  font-weight: 600;
  line-height: 1.25;
}

.deck-actions-group {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}

.deck-stats-fraction {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  font-weight: 800;
  color: var(--primary);
  background: rgba(99, 102, 241, 0.1);
  padding: 3px 8px;
  border-radius: var(--radius-sm);
  letter-spacing: -0.01em;
}

.btn-deck-study {
  padding: 5px 13px;
  border-radius: var(--radius-full);
  font-size: 0.78rem;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  gap: 4px;
  border: 1px solid rgba(99, 102, 241, 0.25);
  background: rgba(99, 102, 241, 0.1);
  color: var(--primary);
  cursor: pointer;
  transition: all var(--transition-normal);
  white-space: nowrap;
  touch-action: manipulation;
}

.btn-deck-study:hover {
  background: var(--primary);
  color: #ffffff;
  border-color: var(--primary);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px var(--primary-glow);
}

.btn-deck-study.due {
  border-color: rgba(245, 158, 11, 0.35);
  background: rgba(245, 158, 11, 0.12);
  color: #f59e0b;
}

.btn-deck-study.due:hover {
  background: #d97706;
  color: #ffffff;
  border-color: #d97706;
  box-shadow: 0 4px 12px rgba(217, 119, 6, 0.25);
}

.deck-chevron {
  color: var(--text-muted);
  font-size: 1.15rem;
  font-weight: 600;
  line-height: 1;
  transition: all var(--transition-fast);
}

.deck-item-card:hover .deck-chevron {
  transform: translateX(3px);
  color: var(--primary);
}

.deck-progress-bar-bg {
  width: 100%;
  height: 5px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-full);
  overflow: hidden;
  display: flex;
}

.deck-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--accent));
  border-radius: var(--radius-full);
  transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* --------------------------------------------------------------------------
   Level 2: Modern YouTube/Messenger/iOS-Style Sleek Subpage Top Bar
   -------------------------------------------------------------------------- */
.yt-subpage-header {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 6px 0 12px 0;
  margin-bottom: 14px;
  border-bottom: 1px solid var(--border);
  background: transparent;
  position: relative;
}

.yt-back-btn {
  width: 38px;
  height: 38px;
  border-radius: var(--radius-full);
  border: 1px solid transparent;
  background: var(--bg-tertiary);
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  flex-shrink: 0;
  transition: all var(--transition-normal);
  -webkit-tap-highlight-color: transparent;
}

.yt-back-btn:hover {
  background: rgba(99, 102, 241, 0.14);
  color: var(--primary);
  transform: scale(1.06);
}

.yt-back-btn:active {
  transform: scale(0.92);
}

.yt-subpage-title-wrap {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.yt-header-title {
  font-size: 1.08rem;
  font-weight: 800;
  color: var(--text-primary);
  letter-spacing: -0.02em;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  line-height: 1.3;
  margin: 0;
}

.yt-header-subtitle {
  font-size: 0.76rem;
  color: var(--text-muted);
  font-weight: 500;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.yt-header-action {
  flex-shrink: 0;
  display: flex;
  align-items: center;
}

/* --------------------------------------------------------------------------
   Level 2: Subpage Layout - Fixed Header & Top Hero with Smooth Content
   -------------------------------------------------------------------------- */
#tab-subtopics,
#tab-subtopic-words {
  display: none;
  flex-direction: column;
  box-sizing: border-box;
}

#tab-subtopics.active,
#tab-subtopic-words.active {
  display: flex;
  flex: 1;
  min-height: 0;
  padding: 8px 12px 14px 12px;
}

#tab-subtopics .subtopics-nav-bar {
  flex-shrink: 0;
  margin-bottom: 12px;
  padding: 0 0 10px 0;
}

#tab-subtopics .subpage-content-body {
  display: flex;
  flex-direction: column;
  flex: 1;
  width: 100%;
  gap: 14px;
}

#tab-subtopics #subpage-hero-container {
  flex-shrink: 0;
  margin-bottom: 2px;
}

#tab-subtopics .subtopics-section-header {
  flex-shrink: 0;
  margin-bottom: 2px;
  margin-top: 2px;
}

#tab-subtopics .subtopics-list-container,
#tab-subtopics .subpage-subtopics-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  width: 100%;
  padding-bottom: 20px;
}

#tab-subtopics .subtopics-list-container::-webkit-scrollbar,
#tab-subtopic-words #subtopic-words-list-container::-webkit-scrollbar {
  width: 5px;
}
#tab-subtopics .subtopics-list-container::-webkit-scrollbar-track,
#tab-subtopic-words #subtopic-words-list-container::-webkit-scrollbar-track {
  background: transparent;
}
#tab-subtopics .subtopics-list-container::-webkit-scrollbar-thumb,
#tab-subtopic-words #subtopic-words-list-container::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 10px;
}

#tab-subtopic-words .yt-subpage-header {
  flex-shrink: 0;
  margin-bottom: 8px;
  padding: 0 0 8px 0;
}

#tab-subtopic-words .subpage-content-body,
#tab-subtopic-words .subtopic-words-container {
  display: flex;
  flex-direction: column;
  flex: 1;
  width: 100%;
  min-height: 0;
}

#tab-subtopic-words .words-toolbar,
#tab-subtopic-words .subtopic-words-toolbar {
  flex-shrink: 0;
  margin-bottom: 8px;
}

#tab-subtopic-words #subtopic-words-list-container,
#tab-subtopic-words .words-list-container,
#tab-subtopic-words .subtopic-words-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  width: 100%;
}

/* Compact Hero Banner Card for Topic */
.subpage-hero-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 18px 20px;
  box-shadow: var(--shadow-sm);
  position: relative;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.subpage-hero-header {
  display: flex;
  align-items: flex-start;
  gap: 14px;
}

.subpage-deck-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  flex-shrink: 0;
  box-shadow: var(--shadow-sm);
}

.subpage-deck-info {
  display: flex;
  flex-direction: column;
  gap: 4px;
  min-width: 0;
  flex: 1;
}

.subpage-deck-title {
  font-size: 1.12rem;
  font-weight: 800;
  color: var(--text-primary);
  letter-spacing: -0.015em;
  line-height: 1.3;
  margin: 0;
}

.subpage-vi-title {
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-secondary);
}

.subpage-deck-meta {
  font-size: 0.78rem;
  color: var(--text-secondary);
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
  margin-top: 3px;
}

.subpage-hero-progress-section {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.subpage-deck-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-secondary);
}

.subpage-deck-footer-left strong {
  color: var(--text-primary);
  font-weight: 700;
}

.subpage-deck-footer-right {
  font-weight: 700;
  color: var(--primary);
  font-family: var(--font-mono);
}

.btn-hero-study {
  width: 100%;
  min-height: 50px;
  padding: 13px 22px;
  font-size: 1rem;
  font-weight: 700;
  border-radius: var(--radius-md);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  background: linear-gradient(135deg, var(--primary), #4f46e5);
  color: #ffffff;
  box-shadow: 0 4px 14px var(--primary-glow);
  transition: all var(--transition-normal);
  border: none;
  cursor: pointer;
  letter-spacing: 0.01em;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.btn-hero-study:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px var(--primary-glow);
}

.btn-hero-study:active {
  transform: scale(0.98);
}

/* Section Header danh sách chủ đề con */
.subtopics-section-header,
.subpage-section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 6px;
  margin-bottom: 10px;
}

.subtopics-section-title,
.subpage-section-title {
  font-size: 1.02rem;
  font-weight: 800;
  color: var(--text-primary);
  letter-spacing: -0.015em;
}

.subtopics-section-meta,
.subpage-count-badge {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-muted);
  background: var(--bg-tertiary);
  padding: 3px 10px;
  border-radius: var(--radius-full);
}

.subtopic-card-btn {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 13px 15px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  cursor: pointer;
  transition: all var(--transition-normal);
  user-select: none;
  position: relative;
  overflow: hidden;
  -webkit-tap-highlight-color: transparent;
  box-shadow: var(--shadow-sm);
}

.subtopic-card-btn:hover {
  transform: translateY(-2px);
  border-color: var(--primary);
  box-shadow: var(--shadow-md);
}

.subtopic-card-btn:active {
  transform: scale(0.985);
}

/* Subtopic Card: Locked Progressive State */
.subtopic-card-btn.locked {
  opacity: 0.72;
  cursor: not-allowed;
  filter: grayscale(0.2);
  border-style: dashed;
  border-color: var(--border);
  background: var(--bg-secondary);
}

.subtopic-card-btn.locked:hover {
  transform: none;
  box-shadow: none;
  border-color: #f59e0b;
}

.subtopic-card-btn.locked .subtopic-icon-badge {
  background: rgba(148, 163, 184, 0.12) !important;
  color: var(--text-muted) !important;
  transform: none !important;
}

.subtopic-card-btn.shake {
  animation: shakeCard 0.4s ease-in-out;
}

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

.subtopic-badge.badge-locked {
  background: rgba(245, 158, 11, 0.12);
  color: #f59e0b;
  border: 1px solid rgba(245, 158, 11, 0.3);
  font-weight: 700;
}

.subtopic-card-top-row {
  display: flex;
  align-items: center;
  gap: 13px;
  width: 100%;
}

.subtopic-icon-badge {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  flex-shrink: 0;
  background: var(--bg-tertiary);
  transition: transform 0.22s cubic-bezier(0.34, 1.56, 0.64, 1), box-shadow 0.22s ease;
  box-shadow: inset 0 1px 1px rgba(255, 255, 255, 0.1);
}

.subtopic-card-btn:hover .subtopic-icon-badge {
  transform: scale(1.08) rotate(2deg);
}

.subtopic-card-info {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.subtopic-card-title {
  font-size: 0.96rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.35;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
  white-space: normal;
}

.subtopic-card-meta {
  font-size: 0.78rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}

.subtopic-count-text {
  font-weight: 600;
  color: var(--text-muted);
}

.subtopic-badge {
  display: inline-flex;
  align-items: center;
  padding: 3px 8px;
  border-radius: var(--radius-sm);
  font-size: 0.72rem;
  font-weight: 700;
  background: var(--bg-tertiary);
  color: var(--text-muted);
  white-space: nowrap;
  letter-spacing: -0.01em;
}

.subtopic-meta-dot {
  color: var(--border);
  font-size: 0.65rem;
}

.subtopic-badge.badge-due {
  background: var(--fsrs-again-bg);
  color: var(--fsrs-again);
}

.subtopic-badge.badge-pinned {
  background: rgba(99, 102, 241, 0.16);
  color: var(--primary);
  border: 1px solid rgba(99, 102, 241, 0.35);
}

.subtopic-badge.badge-done {
  background: var(--fsrs-good-bg);
  color: var(--fsrs-good);
}

.subtopic-badge.badge-learning {
  background: rgba(99, 102, 241, 0.15);
  color: var(--primary-light);
}

.subtopic-badge.badge-recent {
  background: var(--fsrs-hard-bg);
  color: var(--fsrs-hard);
  border: 1px solid rgba(245, 158, 11, 0.3);
}

.subtopic-badge.badge-recommended {
  background: rgba(99, 102, 241, 0.15);
  color: var(--primary);
  border: 1px solid rgba(99, 102, 241, 0.28);
}

.subtopic-badge.badge-new {
  background: rgba(148, 163, 184, 0.12);
  color: var(--text-muted);
}

.subtopic-card-progress {
  width: 100%;
  margin-top: 2px;
}

.subtopic-card-progress .deck-progress-bar-bg {
  height: 4px;
}

.subtopic-mini-progress-bg {
  width: 100%;
  height: 4px;
  background: rgba(148, 163, 184, 0.18);
  border-radius: var(--radius-full);
  overflow: hidden;
  margin-top: 2px;
}

.subtopic-mini-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--accent));
  border-radius: var(--radius-full);
  transition: width 0.3s ease;
}

.subtopic-card-right {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
  text-align: right;
}

.subtopic-stats-fraction {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text-secondary);
}

.subtopic-chevron {
  color: var(--text-muted);
  display: flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
  transition: all var(--transition-fast);
  opacity: 0.6;
}

.subtopic-card-btn:hover .subtopic-chevron {
  transform: translateX(3px);
  color: var(--primary);
  opacity: 1;
}

.badge-tag {
  display: inline-flex;
  align-items: center;
  font-size: 0.72rem;
  font-weight: 700;
  padding: 2px 8px;
  border-radius: var(--radius-sm);
  background: var(--bg-tertiary);
  color: var(--text-secondary);
}

/* --------------------------------------------------------------------------
   Level 4: Vocabulary Subpage Toolbar, Filter Chips & Pagination
   -------------------------------------------------------------------------- */
.subtopic-words-container,
.subpage-words-content {
  display: flex;
  flex-direction: column;
  flex: 1;
  min-height: 0;
  gap: 12px;
}

.subtopic-words-toolbar,
.words-toolbar {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 4px;
}

.subtopic-words-filter-chips,
.words-filter-chips {
  display: flex;
  gap: 8px;
  overflow-x: auto;
  padding: 2px 2px 6px 2px;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}

.subtopic-words-filter-chips::-webkit-scrollbar,
.words-filter-chips::-webkit-scrollbar {
  display: none;
}

.subtopic-words-filter-chip,
.filter-chip {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px 14px;
  border-radius: var(--radius-full);
  font-size: 0.8rem;
  font-weight: 600;
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text-secondary);
  cursor: pointer;
  white-space: nowrap;
  flex-shrink: 0;
  transition: all var(--transition-normal);
  -webkit-tap-highlight-color: transparent;
  user-select: none;
}

.subtopic-words-filter-chip:hover,
.filter-chip:hover {
  border-color: var(--primary);
  color: var(--primary);
  transform: translateY(-1px);
}

.subtopic-words-filter-chip.active,
.filter-chip.active {
  background: var(--primary);
  color: #ffffff;
  border-color: var(--primary);
  box-shadow: 0 2px 10px var(--primary-glow);
}

.chip-count {
  font-size: 0.72rem;
  font-weight: 700;
  padding: 1px 6px;
  border-radius: var(--radius-sm);
  background: var(--bg-tertiary);
  color: inherit;
}

.subtopic-words-filter-chip.active .chip-count,
.filter-chip.active .chip-count {
  background: rgba(255, 255, 255, 0.25);
  color: #ffffff;
}

.words-sub-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
  padding: 4px 2px;
}

.words-sort-wrap,
.words-page-size-wrap {
  display: flex;
  align-items: center;
  gap: 6px;
}

.sort-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-weight: 600;
}

.sort-select {
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-primary);
  border-radius: var(--radius-sm);
  padding: 5px 10px;
  font-size: 0.78rem;
  font-weight: 600;
  outline: none;
  cursor: pointer;
  transition: border-color var(--transition-fast);
}

.sort-select:focus {
  border-color: var(--primary);
}

/* Pagination */
.subtopic-words-pagination,
.words-pagination-container {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  margin-top: 14px;
  margin-bottom: 24px;
  flex-wrap: wrap;
}

.pagination-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  flex-wrap: wrap;
}

.pagination-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 36px;
  height: 36px;
  padding: 0 12px;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text-primary);
  font-size: 0.84rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition-fast);
  user-select: none;
  -webkit-tap-highlight-color: transparent;
}

.pagination-btn:hover:not(:disabled) {
  background: var(--bg-tertiary);
  border-color: var(--primary);
  color: var(--primary);
  transform: translateY(-1px);
}

.pagination-btn.active {
  background: var(--primary);
  border-color: var(--primary);
  color: #ffffff;
  font-weight: 700;
  box-shadow: 0 2px 8px var(--primary-glow);
}

.pagination-dots {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 36px;
  color: var(--text-muted);
  font-weight: 700;
  user-select: none;
}

.pagination-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
  pointer-events: none;
}

.pagination-info {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* --------------------------------------------------------------------------
   Level 3: Subtopic Detail Page & Vocabulary Word Item Cards
   -------------------------------------------------------------------------- */
.subtopic-words-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 12px;
}

.word-item-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  transition: all var(--transition-normal);
  box-shadow: var(--shadow-sm);
}

.word-item-card:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow-md);
  transform: translateY(-1px);
}

.word-card-top-row,
.word-card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}

.word-order-num,
.word-index {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  color: var(--text-muted);
  font-weight: 700;
  flex-shrink: 0;
  opacity: 0.75;
}

.word-main-text-group,
.word-card-header {
  display: flex;
  align-items: baseline;
  gap: 8px;
  flex-wrap: wrap;
  flex: 1;
  min-width: 0;
}

.word-term,
.word-text {
  font-size: 1.08rem;
  font-weight: 800;
  color: var(--text-primary);
  letter-spacing: -0.015em;
  line-height: 1.3;
}

.word-phonetic {
  color: var(--primary);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 500;
}

.word-pos {
  font-size: 0.72rem;
  font-style: italic;
  color: var(--text-muted);
  background: var(--bg-tertiary);
  padding: 1px 6px;
  border-radius: 4px;
  font-weight: 500;
}

.word-cefr {
  font-size: 0.68rem;
  font-weight: 800;
  padding: 1px 6px;
  border-radius: 4px;
  text-transform: uppercase;
  letter-spacing: 0.02em;
}

.word-cefr.a1, .word-cefr.a2 {
  background: rgba(16, 185, 129, 0.15);
  color: #10b981;
}

.word-cefr.b1, .word-cefr.b2 {
  background: rgba(59, 130, 246, 0.15);
  color: #3b82f6;
}

.word-cefr.c1, .word-cefr.c2 {
  background: rgba(168, 85, 247, 0.15);
  color: #a855f7;
}

.word-status-col,
.word-card-actions {
  flex-shrink: 0;
}

.word-status-tag {
  display: inline-flex;
  align-items: center;
  padding: 3px 8px;
  border-radius: 6px;
  font-size: 0.72rem;
  font-weight: 700;
  white-space: nowrap;
  letter-spacing: -0.01em;
}

.word-status-tag.status-new {
  background: rgba(148, 163, 184, 0.14);
  color: var(--text-muted);
}

.word-status-tag.status-due {
  background: var(--fsrs-again-bg);
  color: var(--fsrs-again);
  border: 1px solid rgba(239, 68, 68, 0.25);
}

.word-status-tag.status-done {
  background: var(--fsrs-good-bg);
  color: var(--fsrs-good);
  border: 1px solid rgba(16, 185, 129, 0.25);
}

.word-status-tag.status-learning {
  background: rgba(99, 102, 241, 0.15);
  color: var(--primary-light);
  border: 1px solid rgba(99, 102, 241, 0.25);
}

.word-leech-pill {
  font-size: 0.68rem;
  font-weight: 800;
  padding: 1px 6px;
  border-radius: 4px;
  background: rgba(245, 158, 11, 0.16);
  color: #d97706;
  border: 1px solid rgba(245, 158, 11, 0.35);
  display: inline-flex;
  align-items: center;
  gap: 2px;
}

[data-theme="dark"] .word-leech-pill {
  color: #fbbf24;
  background: rgba(245, 158, 11, 0.22);
  border-color: rgba(245, 158, 11, 0.45);
}

.word-status-tag.status-suspended {
  background: rgba(148, 163, 184, 0.2);
  color: #64748b;
  border: 1px dashed rgba(148, 163, 184, 0.4);
}

[data-theme="dark"] .word-status-tag.status-suspended {
  color: #94a3b8;
  border-color: rgba(255, 255, 255, 0.15);
}

.word-item-card.is-suspended {
  opacity: 0.72;
  border-left: 3px dashed #94a3b8;
}

.btn-word-toggle-suspend,
.btn-word-reset-card {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px 10px;
  border-radius: var(--radius-sm);
  font-size: 0.76rem;
  font-weight: 600;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
  -webkit-tap-highlight-color: transparent;
}

.btn-word-toggle-suspend:hover {
  background: rgba(245, 158, 11, 0.12);
  color: #d97706;
  border-color: #d97706;
  transform: translateY(-1px);
}

.btn-word-toggle-suspend.active {
  background: rgba(16, 185, 129, 0.12);
  color: #10b981;
  border-color: #10b981;
}

.btn-word-reset-card:hover {
  background: rgba(239, 68, 68, 0.1);
  color: #ef4444;
  border-color: #ef4444;
  transform: translateY(-1px);
}

.word-meaning-text,
.word-meaning {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.4;
}

.word-definition {
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.4;
}

.word-example-box {
  background: var(--bg-tertiary);
  border-left: 3px solid var(--primary);
  padding: 8px 12px;
  border-radius: 6px;
  display: flex;
  flex-direction: column;
  gap: 3px;
  margin-top: 2px;
}

.word-example-en {
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-style: normal;
  font-weight: 500;
  line-height: 1.45;
}

.word-example-en .example-highlight {
  font-style: normal;
  font-weight: 700;
  color: var(--primary-light);
  text-decoration: underline;
  text-decoration-color: rgba(99, 102, 241, 0.4);
  text-underline-offset: 2px;
}

[data-theme="dark"] .word-example-en .example-highlight {
  color: #818cf8;
}

.word-example-vi {
  font-size: 0.8rem;
  color: var(--text-muted);
  line-height: 1.4;
  font-style: normal;
  font-weight: 400;
}

.word-card-bottom-actions {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 4px;
}

.btn-word-audio {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  font-weight: 600;
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  color: var(--text-primary);
  cursor: pointer;
  transition: all var(--transition-fast);
  -webkit-tap-highlight-color: transparent;
}

.btn-word-audio:hover {
  background: rgba(99, 102, 241, 0.12);
  color: var(--primary);
  border-color: var(--primary);
  transform: translateY(-1px);
}

.btn-word-study-single {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  font-size: 0.78rem;
  font-weight: 600;
  background: rgba(99, 102, 241, 0.1);
  border: 1px solid rgba(99, 102, 241, 0.3);
  color: var(--primary);
  cursor: pointer;
  transition: all var(--transition-fast);
  -webkit-tap-highlight-color: transparent;
}

.btn-word-study-single:hover {
  background: var(--primary);
  color: #ffffff;
  border-color: var(--primary);
  transform: translateY(-1px);
  box-shadow: 0 3px 10px var(--primary-glow);
}

.words-empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 40px 20px;
  gap: 8px;
  color: var(--text-muted);
  font-size: 0.9rem;
  font-weight: 500;
}

/* Khối thống kê tổng quan chủ đề con */
.subtopic-overview-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  margin-top: 14px;
}

.overview-stat-pill {
  background: var(--bg-tertiary);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 8px 6px;
  text-align: center;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.overview-stat-num {
  font-size: 1.15rem;
  font-weight: 800;
  font-family: var(--font-mono);
  color: var(--text-primary);
  line-height: 1.2;
}

.overview-stat-num.text-success {
  color: #10b981;
}

.overview-stat-num.text-warning {
  color: #f59e0b;
}

.overview-stat-lbl {
  font-size: 0.72rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* Modal Chi tiết Chủ đề con */
.subtopic-modal-dialog {
  max-width: 440px;
  width: 92%;
  border-radius: var(--radius-lg);
  background: var(--bg-card);
  border: 1px solid var(--border);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
  margin: auto;
}

.subtopic-modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 20px 14px 20px;
  border-bottom: 1px solid var(--border);
}

.subtopic-modal-title-group {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
  flex: 1;
}

.subtopic-modal-icon {
  width: 46px;
  height: 46px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.6rem;
  flex-shrink: 0;
  background: rgba(99, 102, 241, 0.12);
}

.subtopic-modal-title-text {
  flex: 1;
  min-width: 0;
}

.subtopic-modal-title {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.25;
  margin: 0;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  letter-spacing: -0.01em;
}

.subtopic-modal-subtitle {
  font-size: 0.8rem;
  color: var(--text-secondary);
  margin-top: 2px;
  font-weight: 500;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.subtopic-modal-body {
  padding: 18px 20px 20px 20px;
}

.subtopic-action-group {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-top: 18px;
}

.btn-modal-action {
  width: 100%;
  padding: 13px 12px;
  font-size: 0.94rem;
  font-weight: 700;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  gap: 6px;
  min-height: 50px;
  box-sizing: border-box;
  cursor: pointer;
  transition: all var(--transition-normal);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.btn-modal-action span {
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.subtopic-action-group .btn-primary-hero {
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #ffffff;
  border: none;
  box-shadow: 0 4px 12px var(--primary-glow);
  min-height: 50px;
  border-radius: var(--radius-md);
}

.subtopic-action-group .btn-primary-hero:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 16px var(--primary-glow);
}

.btn-secondary-action {
  width: 100%;
  border-radius: var(--radius-md);
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 1.5px solid var(--border);
  font-weight: 600;
  font-size: 0.92rem;
  min-height: 50px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  cursor: pointer;
  transition: all var(--transition-normal);
  touch-action: manipulation;
  -webkit-tap-highlight-color: transparent;
}

.btn-secondary-action:hover {
  border-color: var(--primary);
  color: var(--primary);
  background: rgba(99, 102, 241, 0.08);
  transform: translateY(-1px);
}

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

.btn-subtle-close {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  padding: 4px 10px;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.btn-subtle-close:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border-color: var(--text-muted);
}

/* ==========================================================================
   🖥️ DESKTOP STYLING FOR DECKS & SUBTOPICS & WORDS (>= 860px)
   ========================================================================== */
@media (min-width: 860px) {
  #tab-decks,
  #tab-subtopics,
  #tab-subtopic-words {
    max-width: 1100px;
    margin: 0 auto;
    width: 100%;
    box-sizing: border-box;
  }

  .decks-header-bar {
    position: sticky;
    top: -24px;
    z-index: 25;
    background: var(--bg-primary);
    padding-top: 4px;
    padding-bottom: 12px;
    margin-bottom: 16px;
    display: flex;
    flex-direction: column;
    gap: 12px;
  }

  .decks-sub-toolbar {
    display: flex;
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    padding: 0;
  }

  .decks-filter-dropdowns {
    display: flex;
    align-items: center;
    gap: 10px;
    width: auto;
  }

  .decks-select-wrap {
    width: auto;
    min-width: 180px;
  }

  .decks-select-wrap select {
    padding: 7px 28px 7px 12px;
    font-size: 0.82rem;
  }

  .decks-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(360px, 1fr));
    gap: 18px;
  }

  .deck-item-card {
    padding: 18px 20px;
    min-height: 125px;
    border-radius: var(--radius-xl);
  }

  .deck-icon-badge {
    width: 48px;
    height: 48px;
    font-size: 1.5rem;
  }

  .deck-title {
    font-size: 1.1rem;
  }

  .subtopics-list-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 16px;
    margin-bottom: 24px;
  }

  .subtopic-card-btn {
    padding: 16px 18px;
    height: 100%;
    border-radius: var(--radius-lg);
  }

  .subpage-hero-card {
    padding: 16px 20px;
    margin-bottom: 0;
    border-radius: var(--radius-xl);
  }

  .subtopic-words-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
    gap: 14px;
  }

  .word-item-card {
    padding: 14px 16px;
    border-radius: var(--radius-md);
  }

  .words-toolbar {
    position: sticky;
    top: -24px;
    z-index: 25;
    background: var(--bg-primary);
    padding-top: 4px;
    padding-bottom: 12px;
    margin-bottom: 16px;
  }

  .words-filter-chips {
    flex-wrap: wrap;
    gap: 8px;
  }

  .filter-chip {
    padding: 6px 14px;
    font-size: 0.84rem;
  }

  .yt-subpage-header {
    position: static;
    padding: 0 0 16px 0;
    margin-bottom: 18px;
    border-bottom: 1px solid var(--border);
  }

  .subtopic-modal-dialog {
    max-width: 480px;
    border-radius: var(--radius-xl);
  }
}

/* ==========================================================================
   📱 MOBILE STYLING & TOUCH OPTIMIZATIONS (<= 640px)
   ========================================================================== */
@media (max-width: 640px) {
  .yt-subpage-header {
    padding: 8px 0 12px 0;
    margin-bottom: 14px;
    gap: 10px;
    position: sticky;
    top: 0;
    z-index: 20;
    background: var(--bg-primary);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
  }

  .yt-back-btn {
    width: 40px;
    height: 40px;
    min-width: 40px;
    border-radius: var(--radius-md);
  }

  .subpage-hero-card {
    padding: 15px 16px;
    border-radius: var(--radius-lg);
    gap: 12px;
  }

  .subpage-deck-icon {
    width: 44px;
    height: 44px;
    font-size: 1.35rem;
    border-radius: var(--radius-md);
  }

  .btn-hero-study {
    min-height: 48px;
    padding: 12px 18px;
    font-size: 0.98rem;
    border-radius: var(--radius-md);
  }

  .subtopics-list-container {
    gap: 12px;
    margin-bottom: 10px;
  }

  .subtopic-card-btn {
    padding: 14px 15px;
    border-radius: var(--radius-lg);
    gap: 11px;
  }

  .subtopic-icon-badge {
    width: 42px;
    height: 42px;
    font-size: 1.3rem;
  }
}