/* ===================================
   Component Styles
   =================================== */

/* ────────────────────────────────────
   Screens
   ──────────────────────────────────── */

.screen {
  display: none;
  flex-direction: column;
  flex: 1;
  width: 100%;
  padding: var(--space-3) var(--space-4);
  box-sizing: border-box;
  overflow-y: auto;
  overscroll-behavior: contain;
}

.screen.active {
  display: flex;
  animation: screenFadeIn var(--duration-slow) var(--ease-out);
}

/* Session screen is locked to viewport height (no outer scroll) */
#screen-session.active {
  flex: 1;
  height: 100%;
  max-height: 100%;
  overflow: hidden;
  padding: var(--space-2) var(--space-4) var(--space-3);
}

.screen-header {
  padding-top: var(--space-2);
  padding-bottom: var(--space-3);
  flex-shrink: 0;
}

.screen-body {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-height: 0;
}

/* ────────────────────────────────────
   Brand (Chapter screen header)
   ──────────────────────────────────── */

.brand {
  text-align: center;
  padding: var(--space-4) 0 var(--space-2);
}

.brand-icon {
  font-size: 2.5rem;
  margin-bottom: var(--space-2);
  display: inline-block;
  animation: gentleFloat 3s ease-in-out infinite;
}

.brand-title {
  font-size: var(--text-3xl);
  font-weight: 800;
  letter-spacing: -0.02em;
  background: linear-gradient(135deg, var(--text-primary) 0%, var(--primary-200) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.brand-subtitle {
  font-size: var(--text-sm);
  color: var(--text-muted);
  font-weight: 500;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  margin-top: var(--space-1);
}

/* ────────────────────────────────────
   Section Title & Screen Title
   ──────────────────────────────────── */

.section-header-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-3);
}

.section-title {
  font-size: var(--text-xs);
  font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

/* ────────────────────────────────────
   Paper Filter Tabs (Paper I / Paper II)
   ──────────────────────────────────── */

.paper-filter-tabs {
  display: flex;
  gap: var(--space-1);
  padding: var(--space-1);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  margin-bottom: var(--space-4);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.paper-tab {
  flex: 1;
  padding: var(--space-2) var(--space-2);
  font-size: var(--text-xs);
  font-weight: 600;
  color: var(--text-secondary);
  border-radius: var(--radius-md);
  text-align: center;
  white-space: nowrap;
  transition: all var(--duration-fast) var(--ease-in-out);
}

.paper-tab:hover {
  color: var(--text-primary);
  background: rgba(255, 255, 255, 0.04);
}

.paper-tab.active {
  color: white;
  background: linear-gradient(135deg, var(--primary-600), var(--primary-500));
  box-shadow: 0 2px 8px rgba(99, 102, 241, 0.35);
}

.badge-paper {
  display: inline-block;
  padding: 0.15em 0.55em;
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  border-radius: var(--radius-sm);
  background: rgba(99, 102, 241, 0.15);
  border: 1px solid rgba(99, 102, 241, 0.3);
  color: var(--primary-200);
  margin-bottom: var(--space-1);
}

.badge-paper.paper-2 {
  background: rgba(6, 182, 212, 0.15);
  border-color: rgba(6, 182, 212, 0.3);
  color: var(--accent-400);
}

.screen-title {
  font-size: var(--text-2xl);
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-top: var(--space-3);
}

.screen-subtitle {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  margin-top: var(--space-1);
}

/* ────────────────────────────────────
   Back Button
   ──────────────────────────────────── */

.btn-back {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  color: var(--primary-400);
  font-size: var(--text-sm);
  font-weight: 600;
  padding: var(--space-2) 0;
  transition: color var(--duration-fast) var(--ease-in-out);
}

.btn-back:hover {
  color: var(--primary-200);
}

.btn-back svg {
  flex-shrink: 0;
}

/* ────────────────────────────────────
   Chapter Grid & Cards
   ──────────────────────────────────── */

.chapter-grid {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.chapter-card {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  padding: var(--space-5);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  text-align: left;
  transition: all var(--duration-base) var(--ease-out);
  animation: listItemIn var(--duration-slow) var(--ease-out) backwards;
  box-shadow: var(--shadow-sm);
}

.chapter-card:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-default);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.chapter-card:active {
  transform: translateY(0);
  box-shadow: var(--shadow-sm);
}

.chapter-card-number {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--primary-600), var(--primary-500));
  color: white;
  font-weight: 700;
  font-size: var(--text-lg);
  flex-shrink: 0;
  box-shadow: 0 2px 8px rgba(99, 102, 241, 0.3);
}

.chapter-card-content {
  flex: 1;
  min-width: 0;
}

.chapter-card-title {
  font-size: var(--text-lg);
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.3;
}

.chapter-card-desc {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  margin-top: var(--space-1);
  line-height: 1.4;
}

.chapter-card-meta {
  font-size: var(--text-xs);
  color: var(--text-muted);
  margin-top: var(--space-2);
}

.chapter-card-arrow {
  color: var(--text-muted);
  flex-shrink: 0;
  transition: transform var(--duration-fast) var(--ease-out),
              color var(--duration-fast) var(--ease-out);
}

.chapter-card:hover .chapter-card-arrow {
  transform: translateX(3px);
  color: var(--primary-400);
}

/* Staggered entrance for chapter cards */
.chapter-card:nth-child(1)  { animation-delay: 0ms; }
.chapter-card:nth-child(2)  { animation-delay: 50ms; }
.chapter-card:nth-child(3)  { animation-delay: 100ms; }
.chapter-card:nth-child(4)  { animation-delay: 150ms; }
.chapter-card:nth-child(5)  { animation-delay: 200ms; }
.chapter-card:nth-child(6)  { animation-delay: 250ms; }
.chapter-card:nth-child(7)  { animation-delay: 300ms; }
.chapter-card:nth-child(8)  { animation-delay: 350ms; }
.chapter-card:nth-child(9)  { animation-delay: 400ms; }
.chapter-card:nth-child(10) { animation-delay: 450ms; }

/* ────────────────────────────────────
   Topics Toolbar (title + shuffle)
   ──────────────────────────────────── */

.topics-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-2);
  gap: var(--space-2);
}

.topics-toolbar-left {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  min-width: 0;
}

.topics-toolbar .section-title {
  margin-bottom: 0;
  white-space: nowrap;
}

.btn-select-all {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--primary-300);
  background: rgba(99, 102, 241, 0.12);
  border: 1px solid rgba(99, 102, 241, 0.3);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: all var(--duration-fast) var(--ease-in-out);
  user-select: none;
  -webkit-user-select: none;
  line-height: 1.4;
}

.btn-select-all:hover {
  background: rgba(99, 102, 241, 0.24);
  border-color: rgba(99, 102, 241, 0.5);
  color: var(--primary-200);
  transform: translateY(-1px);
}

.btn-select-all:active {
  transform: translateY(0);
}

.btn-select-all.all-selected {
  color: var(--text-secondary);
  background: rgba(255, 255, 255, 0.05);
  border-color: var(--border-default);
}

.btn-select-all.all-selected:hover {
  color: var(--text-primary);
  background: rgba(239, 68, 68, 0.12);
  border-color: rgba(239, 68, 68, 0.3);
}

.select-all-icon-box {
  font-size: 0.7rem;
  font-weight: 700;
  line-height: 1;
}

/* ── Shuffle Toggle ── */

.shuffle-toggle {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  cursor: pointer;
  user-select: none;
  -webkit-user-select: none;
}

.shuffle-checkbox {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
  pointer-events: none;
}

.shuffle-slider {
  position: relative;
  width: 44px;
  height: 24px;
  background: var(--bg-card);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-full);
  transition: all var(--duration-base) var(--ease-in-out);
  flex-shrink: 0;
}

.shuffle-slider::after {
  content: '';
  position: absolute;
  top: 2px;
  left: 2px;
  width: 18px;
  height: 18px;
  background: var(--text-secondary);
  border-radius: 50%;
  transition: all var(--duration-base) var(--ease-out);
}

.shuffle-checkbox:checked + .shuffle-slider {
  background: var(--primary-600);
  border-color: var(--primary-500);
}

.shuffle-checkbox:checked + .shuffle-slider::after {
  transform: translateX(20px);
  background: white;
}

.shuffle-text {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--duration-fast);
}

.shuffle-checkbox:checked ~ .shuffle-text {
  color: var(--primary-400);
}

/* ────────────────────────────────────
   Topic List & Items
   ──────────────────────────────────── */

.topic-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  flex: 1;
  overflow-y: auto;
}

.topic-item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-4) var(--space-5);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-md);
  text-align: left;
  transition: all var(--duration-base) var(--ease-out);
  animation: listItemIn var(--duration-slow) var(--ease-out) backwards;
}

.topic-item:hover {
  background: var(--bg-card-hover);
  border-color: var(--border-default);
}

.topic-item.selected {
  background: rgba(99, 102, 241, 0.1);
  border-color: var(--primary-500);
}

.topic-item:active {
  transform: scale(0.98);
}

/* Custom checkbox visual */
.topic-checkbox-visual {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  border-radius: var(--radius-sm);
  border: 2px solid var(--border-strong);
  flex-shrink: 0;
  transition: all var(--duration-fast) var(--ease-in-out);
  font-size: var(--text-xs);
  font-weight: 700;
  color: transparent;
}

.topic-item.selected .topic-checkbox-visual {
  background: var(--primary-500);
  border-color: var(--primary-500);
  color: white;
  box-shadow: 0 1px 4px rgba(99, 102, 241, 0.3);
}

.topic-item-content {
  flex: 1;
  min-width: 0;
}

.topic-item-title {
  display: block;
  font-size: var(--text-base);
  font-weight: 500;
  color: var(--text-primary);
}

.topic-item-desc {
  display: block;
  font-size: var(--text-xs);
  color: var(--text-secondary);
  margin-top: var(--space-1);
}

.topic-item-meta {
  display: block;
  font-size: var(--text-xs);
  color: var(--text-muted);
  margin-top: var(--space-1);
}

/* Stagger for topic items */
.topic-item:nth-child(1)  { animation-delay: 0ms; }
.topic-item:nth-child(2)  { animation-delay: 40ms; }
.topic-item:nth-child(3)  { animation-delay: 80ms; }
.topic-item:nth-child(4)  { animation-delay: 120ms; }
.topic-item:nth-child(5)  { animation-delay: 160ms; }
.topic-item:nth-child(6)  { animation-delay: 200ms; }
.topic-item:nth-child(7)  { animation-delay: 240ms; }
.topic-item:nth-child(8)  { animation-delay: 280ms; }
.topic-item:nth-child(9)  { animation-delay: 320ms; }
.topic-item:nth-child(10) { animation-delay: 360ms; }

/* ────────────────────────────────────
   Session Start Area
   ──────────────────────────────────── */

.session-start-area {
  padding: var(--space-6) 0 var(--space-4);
  margin-top: auto;
  flex-shrink: 0;
}

.selection-info {
  text-align: center;
  font-size: var(--text-sm);
  color: var(--text-muted);
  margin-bottom: var(--space-3);
  min-height: 1.4em;
  transition: color var(--duration-fast);
}

.selection-info.has-selection {
  color: var(--primary-400);
}

/* ────────────────────────────────────
   Primary Button
   ──────────────────────────────────── */

.btn-primary {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  width: 100%;
  padding: var(--space-4) var(--space-6);
  background: linear-gradient(135deg, var(--primary-600), var(--primary-500));
  color: white;
  font-size: var(--text-lg);
  font-weight: 600;
  border-radius: var(--radius-lg);
  transition: all var(--duration-base) var(--ease-out);
  box-shadow: 0 4px 14px rgba(99, 102, 241, 0.35);
  position: relative;
  overflow: hidden;
}

.btn-primary::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, transparent, rgba(255, 255, 255, 0.1));
  opacity: 0;
  transition: opacity var(--duration-fast);
}

.btn-primary:hover::before {
  opacity: 1;
}

.btn-primary:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
}

.btn-primary:active {
  transform: translateY(1px);
  box-shadow: 0 2px 8px rgba(99, 102, 241, 0.3);
}

.btn-primary:disabled {
  background: var(--bg-card);
  color: var(--text-muted);
  box-shadow: none;
  transform: none;
}

.btn-primary:disabled::before {
  display: none;
}

/* ────────────────────────────────────
   Session Header
   ──────────────────────────────────── */

.session-header {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) 0;
  flex-wrap: wrap;
  flex-shrink: 0;
}

.btn-close {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  color: var(--text-secondary);
  transition: all var(--duration-fast) var(--ease-in-out);
  flex-shrink: 0;
}

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

.session-meta {
  flex: 1;
  min-width: 0;
}

.session-chapter {
  display: block;
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.progress-text {
  display: block;
  font-size: var(--text-xs);
  color: var(--text-muted);
  font-weight: 500;
  font-variant-numeric: tabular-nums;
}

/* ── Progress Bar ── */

.progress-bar-container {
  width: 100%;
  height: 3px;
  background: var(--border-subtle);
  border-radius: var(--radius-full);
  overflow: hidden;
  flex-basis: 100%;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-500), var(--accent-400));
  border-radius: var(--radius-full);
  transition: width var(--duration-slow) var(--ease-out);
  transform-origin: left;
}

/* ────────────────────────────────────
   Session Body
   ──────────────────────────────────── */

.session-body {
  flex: 1;
  display: flex;
  flex-direction: column;
  padding-top: var(--space-3);
  gap: var(--space-3);
  min-height: 0;
}

/* ────────────────────────────────────
   Flashcard
   ──────────────────────────────────── */

.flashcard-container {
  flex: 1;
  display: flex;
  perspective: 1200px;
  min-height: 0;
}

.flashcard {
  width: 100%;
  flex: 1;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

.flashcard-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transition: transform var(--duration-flip) var(--ease-out);
  transform-style: preserve-3d;
}

/* Instant reset when navigating between cards */
.flashcard-inner.no-transition {
  transition: none !important;
}

/* Subtle entrance animation for new card content */
.flashcard-inner.card-entering {
  animation: cardContentEnter 0.3s var(--ease-out);
}

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

/* ── Card Faces ── */

.flashcard-face {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: var(--space-6);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  box-shadow: var(--shadow-lg);
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  overflow-y: auto;
  overflow-x: hidden;
}

.flashcard-back {
  transform: rotateY(180deg);
}

.card-label {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 4px 12px;
  border-radius: var(--radius-full);
  margin-bottom: var(--space-3);
  align-self: flex-start;
  flex-shrink: 0;
  user-select: none;
}

.card-label-question {
  color: var(--primary-300);
  background: rgba(99, 102, 241, 0.15);
  border: 1px solid rgba(99, 102, 241, 0.3);
}

.card-label-answer {
  color: var(--success-300);
  background: rgba(16, 185, 129, 0.15);
  border: 1px solid rgba(16, 185, 129, 0.3);
}

.card-text {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-xl);
  font-weight: 500;
  line-height: 1.5;
  text-align: center;
  color: var(--text-primary);
  word-break: break-word;
  width: 100%;
}

/* ── Card Images ── */

.card-image-container {
  width: 100%;
  max-height: 200px;
  margin-bottom: var(--space-4);
  border-radius: var(--radius-md);
  overflow: hidden;
  flex-shrink: 0;
}

.card-image-container:empty {
  display: none;
  margin: 0;
}

.card-image-container img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  border-radius: var(--radius-md);
}

.card-hint {
  font-size: var(--text-xs);
  color: var(--text-muted);
  margin-top: var(--space-4);
  flex-shrink: 0;
  animation: subtlePulse 3s ease-in-out infinite;
}

/* ────────────────────────────────────
   Navigation Buttons (Prev / Next)
   ──────────────────────────────────── */

.nav-buttons {
  display: flex;
  gap: var(--space-3);
  padding-bottom: var(--space-2);
  flex-shrink: 0;
}

.btn-nav {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-4) var(--space-5);
  border-radius: var(--radius-lg);
  font-size: var(--text-base);
  font-weight: 600;
  transition: all var(--duration-base) var(--ease-out);
  min-height: 52px;
}

.btn-prev-nav {
  flex: 0 0 auto;
  min-width: 120px;
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  color: var(--text-secondary);
}

.btn-prev-nav:hover:not(:disabled) {
  background: var(--bg-card-hover);
  color: var(--text-primary);
  border-color: var(--border-default);
}

.btn-prev-nav:active:not(:disabled) {
  transform: scale(0.97);
}

.btn-prev-nav:disabled {
  opacity: 0.3;
}

.btn-next-nav {
  flex: 1;
  background: linear-gradient(135deg, var(--primary-600), var(--primary-500));
  color: white;
  box-shadow: 0 4px 14px rgba(99, 102, 241, 0.35);
}

.btn-next-nav:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 20px rgba(99, 102, 241, 0.4);
}

.btn-next-nav:active {
  transform: translateY(1px);
  box-shadow: 0 2px 8px rgba(99, 102, 241, 0.3);
}

.btn-next-nav.btn-complete {
  background: linear-gradient(135deg, var(--success-500), var(--success-400));
  box-shadow: 0 4px 14px rgba(16, 185, 129, 0.35);
}

.btn-next-nav.btn-complete:hover {
  box-shadow: 0 6px 20px rgba(16, 185, 129, 0.4);
}

/* ────────────────────────────────────
   Empty State
   ──────────────────────────────────── */

.empty-state {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--space-12) var(--space-6);
}

.empty-state[hidden] {
  display: none;
}

.empty-state-icon {
  font-size: 3rem;
  margin-bottom: var(--space-4);
  opacity: 0.6;
}

.empty-state-title {
  font-size: var(--text-xl);
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: var(--space-2);
}

.empty-state-text {
  font-size: var(--text-sm);
  color: var(--text-muted);
  line-height: 1.7;
  max-width: 280px;
}

/* ────────────────────────────────────
   Responsive Adjustments
   ──────────────────────────────────── */

@media (min-width: 768px) {
  .flashcard-face {
    padding: var(--space-8);
  }

  .card-text {
    font-size: var(--text-2xl);
  }

  .card-image-container {
    max-height: 260px;
  }

  .brand-title {
    font-size: var(--text-4xl);
  }

  .btn-nav {
    min-height: 56px;
    font-size: var(--text-lg);
  }
}

@media (max-height: 600px) {
  .brand {
    padding: var(--space-4) 0 var(--space-2);
  }

  .brand-icon {
    font-size: 2rem;
  }

  .flashcard-face {
    padding: var(--space-4);
  }

  .card-hint {
    display: none;
  }
}

/* ────────────────────────────────────
   Main Mode Switcher (Flashcards vs Notes)
   ──────────────────────────────────── */

.main-mode-switcher {
  display: flex;
  background: var(--surface-secondary);
  padding: 4px;
  border-radius: var(--radius-lg);
  margin-bottom: var(--space-4);
  border: 1px solid var(--border-subtle);
  gap: 4px;
}

.mode-tab {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 14px;
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--text-muted);
  background: transparent;
  border: none;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--duration-fast) var(--ease-out);
}

.mode-tab.active {
  color: #fff;
  background: var(--primary-600);
  box-shadow: 0 2px 8px rgba(37, 99, 235, 0.35);
}

.mode-tab-icon {
  font-size: 1.1rem;
}

/* ────────────────────────────────────
   PDF Action Chip on Chapter Card
   ──────────────────────────────────── */

.chapter-actions-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 8px;
  flex-wrap: wrap;
}

.btn-chip-pdf {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: rgba(16, 185, 129, 0.12);
  color: #10b981;
  border: 1px solid rgba(16, 185, 129, 0.25);
  padding: 5px 10px;
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--duration-fast);
}

.btn-chip-pdf:hover, .btn-chip-pdf:active {
  background: rgba(16, 185, 129, 0.24);
  transform: translateY(-1px);
}

.btn-chip-pdf svg {
  width: 14px;
  height: 14px;
}

/* ────────────────────────────────────
   PDF Viewer Screen Styles
   ──────────────────────────────────── */

#screen-pdf-viewer {
  padding: 0;
  height: 100vh;
  max-height: 100vh;
  overflow: hidden;
  background: #0b1120;
  position: relative;
}

.pdf-viewer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: env(safe-area-inset-top, 10px) 14px 10px;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  z-index: 20;
  flex-shrink: 0;
}

.pdf-header-info {
  flex: 1;
  text-align: center;
  padding: 0 10px;
  min-width: 0;
}

.pdf-title {
  font-size: var(--text-sm);
  font-weight: 700;
  color: #f8fafc;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  margin: 0;
}

.pdf-subtitle {
  font-size: 0.7rem;
  color: var(--text-muted);
  display: block;
}

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

.btn-icon-sm {
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.12);
  color: #e2e8f0;
  border-radius: var(--radius-md);
  width: 34px;
  height: 34px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--duration-fast);
}

.btn-icon-sm:hover, .btn-icon-sm:active {
  background: rgba(255, 255, 255, 0.18);
  color: #fff;
}

.pdf-viewer-body {
  flex: 1;
  overflow: auto;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px 8px;
  -webkit-overflow-scrolling: touch;
  background: radial-gradient(circle at 50% 50%, #172033 0%, #0b1120 100%);
}

.pdf-canvas-wrapper {
  display: inline-block;
  box-shadow: 0 12px 36px rgba(0, 0, 0, 0.65);
  border-radius: 4px;
  overflow: hidden;
  background: #fff;
  transition: transform 0.15s ease-out;
}


#pdf-canvas {
  display: block;
  max-width: 100%;
  height: auto;
}

.pdf-viewer-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 16px calc(env(safe-area-inset-bottom, 10px) + 6px);
  background: rgba(15, 23, 42, 0.9);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  z-index: 20;
  flex-shrink: 0;
}

.btn-pdf-nav {
  display: flex;
  align-items: center;
  gap: 6px;
  background: var(--surface-card);
  border: 1px solid var(--border-subtle);
  color: #e2e8f0;
  padding: 8px 16px;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--duration-fast);
}

.btn-pdf-nav:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.btn-pdf-nav:not(:disabled):hover, .btn-pdf-nav:not(:disabled):active {
  background: var(--primary-600);
  border-color: var(--primary-500);
  color: #fff;
}

.pdf-page-indicator {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: var(--text-sm);
  font-weight: 600;
  color: #cbd5e1;
}

#pdf-page-input {
  width: 48px;
  padding: 4px 6px;
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: var(--radius-sm);
  color: #fff;
  font-size: var(--text-sm);
  font-weight: 700;
  text-align: center;
}

.pdf-loading-overlay {
  position: absolute;
  inset: 0;
  background: rgba(11, 17, 32, 0.85);
  backdrop-filter: blur(8px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 10;
  gap: 16px;
}

.pdf-spinner {
  width: 44px;
  height: 44px;
  border: 3px solid rgba(59, 130, 246, 0.2);
  border-top-color: #3b82f6;
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

.pdf-loading-text {
  font-size: var(--text-sm);
  font-weight: 600;
  color: #94a3b8;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ────────────────────────────────────
   Home Screen (Simplified & Minimal)
   ──────────────────────────────────── */

.home-body {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  max-width: 440px;
  width: 100%;
  margin: 0 auto;
  min-height: calc(100vh - 160px);
  padding: var(--space-4) var(--space-2);
}

.home-hero-header {
  padding-top: var(--space-6);
  padding-bottom: var(--space-4);
  text-align: center;
}

.home-action-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 14px;
  width: 100%;
}

/* Flashcards Button */
.btn-main-flashcards {
  position: relative;
  width: 100%;
  padding: 26px 20px;
  border-radius: 20px;
  background: linear-gradient(145deg, #1e293b, #0f172a);
  border: 1px solid rgba(59, 130, 246, 0.5);
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  cursor: pointer;
  box-shadow: 0 10px 24px -4px rgba(0, 0, 0, 0.35);
  transition: transform var(--duration-fast) var(--ease-out),
              border-color var(--duration-fast) var(--ease-out);
  -webkit-tap-highlight-color: transparent;
}

.btn-main-flashcards-title {
  font-size: 1.5rem;
  font-weight: 800;
  color: #ffffff;
  letter-spacing: -0.01em;
}

.btn-main-flashcards:hover,
.btn-main-flashcards:focus-visible {
  transform: translateY(-2px);
  border-color: #3b82f6;
}

.btn-main-flashcards:active {
  transform: translateY(0);
}

/* Sub Row: PDF & PYQs Equal 50/50 Area */
.home-sub-row {
  display: flex;
  gap: 12px;
  width: 100%;
}

.btn-sub-action {
  flex: 1;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 16px 12px;
  border-radius: 16px;
  background: var(--surface-card);
  border: 1px solid var(--border-subtle);
  color: #cbd5e1;
  font-size: 1.1rem;
  font-weight: 700;
  cursor: pointer;
  box-shadow: 0 6px 16px -4px rgba(0, 0, 0, 0.25);
  transition: transform var(--duration-fast) var(--ease-out),
              border-color var(--duration-fast) var(--ease-out),
              color var(--duration-fast) var(--ease-out);
  -webkit-tap-highlight-color: transparent;
}

.btn-sub-text {
  letter-spacing: 0.02em;
}

.btn-sub-pdf:hover,
.btn-sub-pdf:focus-visible {
  border-color: #10b981;
  color: #34d399;
  transform: translateY(-2px);
}

.btn-sub-pyqs:hover,
.btn-sub-pyqs:focus-visible {
  border-color: #a855f7;
  color: #c084fc;
  transform: translateY(-2px);
}

/* ────────────────────────────────────
   Paper Selection Screen (Simplified)
   ──────────────────────────────────── */

.paper-select-grid {
  display: flex;
  flex-direction: column;
  gap: 14px;
  max-width: 440px;
  width: 100%;
  margin: var(--space-4) auto 0;
}

.paper-select-card {
  width: 100%;
  padding: 24px 20px;
  border-radius: var(--radius-lg);
  background: var(--surface-card);
  border: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  cursor: pointer;
  box-shadow: 0 6px 18px -4px rgba(0, 0, 0, 0.3);
  transition: transform var(--duration-fast) var(--ease-out),
              border-color var(--duration-fast) var(--ease-out);
  -webkit-tap-highlight-color: transparent;
}

.paper-select-card .paper-card-title {
  font-size: 1.35rem;
  font-weight: 800;
  color: #ffffff;
  margin: 0;
}

.paper-select-card:hover,
.paper-select-card:focus-visible {
  transform: translateY(-2px);
  border-color: var(--primary-500);
}

.paper-select-card:active {
  transform: translateY(0);
}

.note-card-number {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-md);
  background: rgba(59, 130, 246, 0.15);
  border: 1px solid rgba(59, 130, 246, 0.3);
  color: var(--primary-400);
  font-weight: 800;
  font-size: 14px;
  flex-shrink: 0;
}


/* ────────────────────────────────────
   PYQs Viewer Screen
   ──────────────────────────────────── */

.pyq-viewer-header {
  padding-top: var(--space-2);
  padding-bottom: var(--space-3);
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  margin-bottom: var(--space-4);
}

.pyq-header-top-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
}

.btn-reveal-all {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border-radius: 16px;
  background: rgba(59, 130, 246, 0.15);
  border: 1px solid rgba(59, 130, 246, 0.35);
  color: #60a5fa;
  font-size: 12px;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--duration-fast);
  -webkit-tap-highlight-color: transparent;
}

.btn-reveal-all:hover, .btn-reveal-all:active {
  background: var(--primary-600);
  border-color: var(--primary-500);
  color: #fff;
}

.pyq-header-title-area {
  margin-top: 4px;
}

.pyq-viewer-body {
  max-width: 680px;
  width: 100%;
  margin: 0 auto;
  padding-bottom: var(--space-8);
}

.pyq-questions-container {
  display: flex;
  flex-direction: column;
  gap: 24px;
}

.pyq-section-group {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.pyq-section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-bottom: 6px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.pyq-section-heading {
  font-size: 14px;
  font-weight: 800;
  color: #94a3b8;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin: 0;
}

.pyq-count-badge {
  font-size: 11px;
  font-weight: 600;
  color: #64748b;
  background: rgba(255, 255, 255, 0.05);
  padding: 2px 8px;
  border-radius: 10px;
}

.pyq-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.pyq-item {
  background: var(--surface-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
  transition: border-color var(--duration-fast);
}

.pyq-item-top {
  display: flex;
  align-items: flex-start;
  gap: 12px;
}

.pyq-q-number {
  font-size: 12px;
  font-weight: 800;
  color: var(--primary-400);
  background: rgba(59, 130, 246, 0.12);
  border: 1px solid rgba(59, 130, 246, 0.25);
  padding: 3px 8px;
  border-radius: 6px;
  flex-shrink: 0;
  margin-top: 2px;
}

.pyq-q-body {
  flex: 1;
  min-width: 0;
}

.pyq-q-text {
  font-size: 15px;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.5;
  margin: 0;
}

.pyq-item-meta {
  margin-top: 8px;
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.pyq-year-pill {
  font-size: 11px;
  font-weight: 700;
  color: #fbbf24;
  background: rgba(245, 158, 11, 0.12);
  border: 1px solid rgba(245, 158, 11, 0.25);
  padding: 2px 8px;
  border-radius: 8px;
  letter-spacing: 0.02em;
}

.pyq-actions {
  display: flex;
  align-items: center;
  justify-content: flex-start;
  margin-top: 2px;
}

.btn-toggle-answer {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.12);
  color: #cbd5e1;
  font-size: 12px;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--duration-fast) var(--ease-out);
  -webkit-tap-highlight-color: transparent;
}

.btn-toggle-answer:hover, .btn-toggle-answer.active {
  background: rgba(16, 185, 129, 0.18);
  border-color: rgba(16, 185, 129, 0.4);
  color: #34d399;
}

.pyq-answer-container {
  margin-top: 6px;
}

.pyq-answer-box {
  background: rgba(15, 23, 42, 0.8);
  border-left: 3px solid #10b981;
  border-radius: 0 8px 8px 0;
  padding: 12px 14px;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.pyq-answer-tag {
  font-size: 10px;
  font-weight: 800;
  color: #34d399;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.pyq-answer-text {
  font-size: 14px;
  font-weight: 500;
  color: #e2e8f0;
  line-height: 1.55;
  word-break: break-word;
}



/* ────────────────────────────────────
   Paper Selection Screen
   ──────────────────────────────────── */

.paper-select-grid {
  display: flex;
  flex-direction: column;
  gap: 16px;
  max-width: 560px;
  width: 100%;
  margin: 0 auto;
}

.paper-select-card {
  position: relative;
  width: 100%;
  padding: 22px;
  border-radius: var(--radius-xl);
  background: var(--surface-card);
  border: 1px solid var(--border-subtle);
  display: flex;
  flex-direction: column;
  gap: 12px;
  text-align: left;
  cursor: pointer;
  box-shadow: 0 8px 20px -4px rgba(0, 0, 0, 0.3);
  transition: transform var(--duration-fast) var(--ease-out),
              border-color var(--duration-fast) var(--ease-out),
              box-shadow var(--duration-fast) var(--ease-out);
  -webkit-tap-highlight-color: transparent;
}

.paper-select-card:hover, .paper-select-card:focus-visible {
  transform: translateY(-2px);
  border-color: rgba(59, 130, 246, 0.5);
  box-shadow: 0 14px 28px -5px rgba(0, 0, 0, 0.4);
}

.paper-select-card:active {
  transform: translateY(0);
}

.paper-card-badge {
  align-self: flex-start;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 3px 10px;
  border-radius: 12px;
  background: rgba(59, 130, 246, 0.18);
  color: #60a5fa;
  border: 1px solid rgba(59, 130, 246, 0.3);
}

.paper-card-badge.badge-p2 {
  background: rgba(168, 85, 247, 0.18);
  color: #c084fc;
  border-color: rgba(168, 85, 247, 0.3);
}

.paper-card-title {
  font-size: var(--text-2xl);
  font-weight: 800;
  color: var(--text-primary);
  margin: 0;
}

.paper-card-desc {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  line-height: 1.5;
  margin: 0;
}

.paper-card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  font-size: var(--text-xs);
  color: var(--text-muted);
  font-weight: 600;
  padding: 8px 0;
}

.paper-card-action {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 4px;
  padding-top: 12px;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--primary-400);
}

/* ────────────────────────────────────
   PDF Notes Menu Screen
   ──────────────────────────────────── */

.notes-menu-container {
  display: flex;
  flex-direction: column;
  gap: 24px;
  max-width: 600px;
  width: 100%;
  margin: 0 auto;
  padding-bottom: var(--space-6);
}

.notes-section {
  background: var(--surface-subtle);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: 18px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.notes-section-header {
  display: flex;
  align-items: center;
  gap: 12px;
}

.notes-section-title {
  font-size: var(--text-lg);
  font-weight: 800;
  color: var(--text-primary);
  margin: 0;
}

.notes-grid {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.note-card {
  position: relative;
  width: 100%;
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 16px;
  border-radius: var(--radius-lg);
  background: var(--surface-card);
  border: 1px solid var(--border-subtle);
  text-align: left;
  cursor: pointer;
  transition: transform var(--duration-fast),
              border-color var(--duration-fast),
              background var(--duration-fast);
  -webkit-tap-highlight-color: transparent;
}

.note-card:hover, .note-card:focus-visible {
  transform: translateY(-2px);
  border-color: rgba(59, 130, 246, 0.4);
  background: var(--surface-raised);
}

.note-card:active {
  transform: translateY(0);
}

.note-card-number {
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: var(--surface-secondary);
  border: 1px solid var(--border-subtle);
  font-size: var(--text-sm);
  font-weight: 700;
  color: var(--primary-400);
  flex-shrink: 0;
}

.note-card-content {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.note-card-title {
  font-size: var(--text-base);
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.35;
}

.note-card-meta {
  font-size: 12px;
  color: var(--text-muted);
  font-weight: 500;
}

.badge-offline {
  display: inline-block;
  padding: 1px 6px;
  border-radius: 4px;
  background: rgba(16, 185, 129, 0.15);
  color: var(--success-400);
  font-size: 11px;
  font-weight: 600;
}

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

.btn-note-open {
  padding: 6px 14px;
  border-radius: var(--radius-md);
  background: var(--primary-600);
  color: #ffffff;
  font-size: var(--text-xs);
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: background var(--duration-fast);
}

.btn-note-open:hover {
  background: var(--primary-500);
}

.btn-note-download {
  padding: 6px 14px;
  border-radius: var(--radius-md);
  background: var(--surface-secondary);
  border: 1px solid var(--border-default);
  color: var(--text-primary);
  font-size: var(--text-xs);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--duration-fast);
}

.btn-note-download:hover {
  background: var(--primary-600);
  border-color: var(--primary-600);
  color: #ffffff;
}

.btn-note-delete {
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  background: transparent;
  border: 1px solid var(--border-subtle);
  color: var(--text-muted);
  font-size: 11px;
  cursor: pointer;
  transition: all var(--duration-fast);
}

.btn-note-delete:hover {
  background: rgba(239, 68, 68, 0.15);
  border-color: var(--danger-500);
  color: var(--danger-400);
}

.note-card-downloading {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-top: 4px;
}

.download-progress-bar {
  width: 100%;
  height: 4px;
  background: var(--surface-secondary);
  border-radius: 2px;
  overflow: hidden;
}

.download-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-500), var(--accent-400));
  border-radius: 2px;
  transition: width 0.15s ease-out;
}

/* ────────────────────────────────────
   App Update Notification Modal
   ──────────────────────────────────── */

.app-update-modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.7);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 20px;
  animation: fadeIn 0.2s ease-out;
}

.app-update-modal {
  width: 100%;
  max-width: 400px;
  background: var(--surface-card);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-xl);
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.5);
  animation: modalSlideUp 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

.update-modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.update-modal-title {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--text-primary);
  margin: 0;
}

.update-modal-badge {
  font-size: 12px;
  font-weight: 700;
  background: rgba(99, 102, 241, 0.2);
  color: var(--primary-400);
  padding: 3px 8px;
  border-radius: 6px;
}

.update-modal-text {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  line-height: 1.5;
  margin: 0;
}

.update-modal-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: 6px;
}

.btn-update-primary {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 12px 18px;
  background: linear-gradient(135deg, var(--primary-600), var(--primary-500));
  color: #ffffff;
  font-size: var(--text-sm);
  font-weight: 600;
  border-radius: var(--radius-lg);
  text-decoration: none;
  transition: transform var(--duration-fast), opacity var(--duration-fast);
}

.btn-update-primary:hover {
  opacity: 0.95;
  transform: translateY(-1px);
}

.btn-update-secondary {
  padding: 12px 18px;
  background: var(--surface-secondary);
  color: var(--text-muted);
  font-size: var(--text-sm);
  font-weight: 600;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-subtle);
  cursor: pointer;
  transition: color var(--duration-fast);
}

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

@keyframes modalSlideUp {
  from {
    opacity: 0;
    transform: translateY(20px) scale(0.96);
  }
/* ────────────────────────────────────
   Landscape & Compact Viewport Optimizations
   ──────────────────────────────────── */

@media (orientation: landscape) and (max-height: 600px) {
  /* Screens General */
  .screen {
    padding: var(--space-2) var(--space-4);
  }

  .screen-header {
    padding-top: var(--space-1);
    padding-bottom: var(--space-2);
  }

  .screen-title {
    font-size: var(--text-xl);
    margin-top: var(--space-1);
  }

  /* Home Screen */
  .home-screen-header {
    margin-bottom: var(--space-3);
  }

  .home-cards-container {
    display: grid;
    grid-template-columns: 1.2fr 1fr;
    gap: 12px;
    align-items: stretch;
    max-width: 800px;
    margin: 0 auto;
  }

  .home-sub-row {
    flex-direction: column;
    gap: 10px;
  }

  .btn-main-flashcards {
    height: 100%;
    min-height: 120px;
    padding: 16px;
  }

  .btn-main-flashcards-title {
    font-size: 1.25rem;
  }

  .btn-sub-action {
    padding: 12px 14px;
    font-size: 1rem;
    flex: 1;
  }

  /* Paper Selection */
  .paper-select-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 14px;
    max-width: 680px;
  }

  .paper-select-card {
    padding: 16px;
  }

  .paper-select-card .paper-card-title {
    font-size: 1.15rem;
  }

  /* Chapters Grid */
  .chapter-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 10px;
  }

  .chapter-card {
    padding: 10px 14px;
    gap: 12px;
  }

  .chapter-card-number {
    width: 36px;
    height: 36px;
    font-size: var(--text-base);
  }

  .chapter-card-title {
    font-size: var(--text-base);
  }

  /* Topics Selection */
  .topic-list {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 8px;
  }

  .topic-item {
    padding: 8px 12px;
    gap: 10px;
  }

  .topic-item-title {
    font-size: var(--text-sm);
  }

  .session-start-area {
    padding: var(--space-2) 0;
  }

  .btn-primary {
    padding: 10px 16px;
    font-size: var(--text-base);
  }

  /* Flashcard Session */
  #screen-session.active {
    padding: 4px var(--space-4) 8px;
  }

  .session-header {
    padding: 2px 0 4px;
    gap: 8px;
  }

  .btn-close {
    width: 30px;
    height: 30px;
  }

  .session-chapter {
    font-size: 0.82rem;
  }

  .session-body {
    padding-top: 4px;
    gap: 6px;
  }

  .flashcard-face {
    padding: 10px 18px;
    border-radius: var(--radius-lg);
  }

  .card-label {
    font-size: 0.65rem;
    margin-bottom: 2px;
  }

  .card-text {
    font-size: 1.1rem;
    line-height: 1.35;
  }

  .card-image-container {
    max-height: 120px;
    margin-bottom: 4px;
  }

  .card-hint {
    display: none;
  }

  .nav-buttons {
    padding-bottom: 0;
    gap: 10px;
  }

  .btn-nav {
    min-height: 38px;
    padding: 6px 14px;
    font-size: 0.9rem;
    border-radius: var(--radius-md);
  }

  .btn-prev-nav {
    min-width: 90px;
  }

  /* Notes Menu Grid */
  .notes-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 10px;
  }

  .note-card {
    padding: 10px 12px;
  }

  /* PDF Viewer in Landscape */
  .pdf-viewer-header {
    padding: 4px 12px;
  }

  .pdf-viewer-footer {
    padding: 4px 12px;
    min-height: 42px;
  }

  .btn-pdf-nav {
    min-width: 70px;
    padding: 6px 12px;
    font-size: 12px;
  }

  /* PYQs List in Landscape */
  .pyqs-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 10px;
  }

  .pyq-item {
    padding: 12px;
    gap: 8px;
  }
}