:root {
  --bg-main: #090d16;
  --bg-card: #151d2f;
  --bg-card-hover: #1c263c;
  --bg-subtle: #243048;
  --border: #2d3d5b;
  
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  
  /* Subject Theme: Dynamic */
  --subject-accent: #10b981;
  --subject-gradient: linear-gradient(135deg, #10b981, #059669);
  
  --ahaana-accent: #38bdf8;
  --ahaana-bg: rgba(56, 189, 248, 0.08);
  --ahaana-border: rgba(56, 189, 248, 0.3);
  
  --ref-accent: #c084fc;
  --ref-bg: rgba(192, 132, 252, 0.08);
  --ref-border: rgba(192, 132, 252, 0.3);
  
  --enh-accent: #34d399;
  --enh-bg: rgba(52, 211, 153, 0.08);
  --enh-border: rgba(52, 211, 153, 0.3);

  --warning-bg: rgba(245, 158, 11, 0.15);
  --warning-border: #f59e0b;
  --warning-text: #fbbf24;
}

/* Subject Themes */
body.theme-biology {
  --subject-accent: #10b981;
  --subject-gradient: linear-gradient(135deg, #10b981, #059669);
}
body.theme-chemistry {
  --subject-accent: #f59e0b;
  --subject-gradient: linear-gradient(135deg, #f59e0b, #d97706);
}
body.theme-physics {
  --subject-accent: #6366f1;
  --subject-gradient: linear-gradient(135deg, #6366f1, #4f46e5);
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background-color: var(--bg-main);
  color: var(--text-primary);
  line-height: 1.45;
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  user-select: none;
}

/* iPad Header */
header {
  background-color: #111827;
  border-bottom: 1px solid var(--border);
  padding: 10px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-shrink: 0;
  gap: 16px;
}

.brand-area {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: #fff;
  display: flex;
  align-items: center;
  gap: 6px;
}

.brand-title span {
  background: var(--subject-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-weight: 800;
}

.brand-subtitle {
  font-size: 0.75rem;
  color: var(--text-secondary);
}

/* Segmented Control / Subject Tabs */
.subject-tabs {
  display: flex;
  background-color: var(--bg-card);
  border: 1px solid var(--border);
  padding: 4px;
  border-radius: 12px;
  gap: 4px;
}

.subject-tab {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 18px;
  border-radius: 8px;
  font-size: 0.88rem;
  font-weight: 600;
  color: var(--text-secondary);
  background: transparent;
  border: none;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  min-height: 40px;
}

.subject-tab:hover {
  color: #fff;
  background-color: rgba(255, 255, 255, 0.05);
}

.subject-tab.active {
  background: var(--subject-gradient);
  color: #fff;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.4);
}

/* Header Stats */
.header-stats {
  display: flex;
  align-items: center;
  gap: 10px;
}

.stat-pill {
  background-color: var(--bg-card);
  border: 1px solid var(--border);
  padding: 6px 12px;
  border-radius: 9999px;
  font-size: 0.78rem;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 6px;
}

.stat-pill.ahaana { color: var(--ahaana-accent); border-color: var(--ahaana-border); }
.stat-pill.ref { color: var(--ref-accent); border-color: var(--ref-border); }
.stat-pill.coverage { background-color: rgba(16, 185, 129, 0.15); color: #34d399; border-color: rgba(16, 185, 129, 0.4); }

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

.btn {
  padding: 8px 16px;
  border-radius: 8px;
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: all 0.15s ease;
  min-height: 40px;
}

.btn-primary {
  background: var(--subject-gradient);
  color: white;
}
.btn-primary:hover {
  filter: brightness(1.1);
}

.btn-export {
  background: linear-gradient(135deg, #0ea5e9, #0284c7);
  color: white;
}
.btn-export:hover {
  background: #0369a1;
}

.btn-subtle {
  background-color: var(--bg-subtle);
  color: var(--text-primary);
  border: 1px solid var(--border);
}
.btn-subtle:hover {
  background-color: var(--border);
}

/* App Container */
.app-container {
  display: flex;
  flex: 1;
  overflow: hidden;
}

/* Sidebar */
aside.topic-sidebar {
  width: 320px;
  background-color: #0e1422;
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  flex-shrink: 0;
  transition: width 0.25s ease;
}

aside.topic-sidebar.collapsed {
  width: 0;
  overflow: hidden;
  border-right: none;
}

.sidebar-header {
  padding: 12px 14px;
  border-bottom: 1px solid var(--border);
}

.search-input {
  width: 100%;
  background-color: var(--bg-card);
  border: 1px solid var(--border);
  padding: 10px 12px;
  border-radius: 8px;
  color: #fff;
  font-size: 0.85rem;
  outline: none;
  min-height: 40px;
}
.search-input:focus {
  border-color: var(--subject-accent);
}

.filter-bar {
  margin-top: 8px;
  display: flex;
  gap: 6px;
}

.filter-btn {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-secondary);
  font-size: 0.75rem;
  padding: 6px 10px;
  border-radius: 6px;
  cursor: pointer;
  min-height: 32px;
}
.filter-btn.active {
  background-color: var(--subject-accent);
  color: #090d16;
  border-color: var(--subject-accent);
  font-weight: 700;
}

.topic-list {
  flex: 1;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  padding: 10px;
}

.topic-item {
  padding: 12px 14px;
  margin-bottom: 8px;
  border-radius: 10px;
  background-color: var(--bg-card);
  border: 1px solid transparent;
  cursor: pointer;
  transition: all 0.15s ease;
}

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

.topic-item.active {
  border-color: var(--subject-accent);
  background-color: rgba(255, 255, 255, 0.06);
  box-shadow: inset 3px 0 0 var(--subject-accent);
}

.topic-item-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 4px;
}

.topic-title {
  font-size: 0.85rem;
  font-weight: 600;
  color: #f1f5f9;
}

.badge {
  font-size: 0.65rem;
  font-weight: 700;
  padding: 2px 6px;
  border-radius: 4px;
  text-transform: uppercase;
}

.badge-covered { background-color: rgba(34, 197, 94, 0.2); color: #4ade80; border: 1px solid rgba(34, 197, 94, 0.4); }
.badge-partial { background-color: rgba(234, 179, 8, 0.2); color: #facc15; border: 1px solid rgba(234, 179, 8, 0.4); }
.badge-missing { background-color: rgba(239, 68, 68, 0.2); color: #f87171; border: 1px solid rgba(239, 68, 68, 0.4); }

.topic-meta {
  display: flex;
  justify-content: space-between;
  font-size: 0.72rem;
  color: var(--text-muted);
}

/* Main Studio */
main.studio-area {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background-color: var(--bg-main);
}

.active-topic-banner {
  background: #111827;
  border-bottom: 1px solid var(--border);
  padding: 12px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.sidebar-toggle-btn {
  background: var(--bg-subtle);
  border: 1px solid var(--border);
  color: var(--text-primary);
  border-radius: 6px;
  padding: 6px 10px;
  cursor: pointer;
  margin-right: 12px;
  font-size: 0.9rem;
}

.active-topic-info h2 {
  font-size: 1.15rem;
  font-weight: 700;
  color: #fff;
}

.active-topic-info p {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

/* 3 Column Grid (iPad Side-by-Side) */
.columns-grid {
  flex: 1;
  display: grid;
  grid-template-columns: 1fr 1fr 1.1fr;
  gap: 14px;
  padding: 14px;
  overflow: hidden;
}

@media (max-width: 900px) {
  .columns-grid {
    grid-template-columns: 1fr;
    overflow-y: auto;
  }
}

.column {
  background-color: #0e1422;
  border: 1px solid var(--border);
  border-radius: 12px;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.column.ahaana-col { border-top: 4px solid var(--ahaana-accent); }
.column.ref-col { border-top: 4px solid var(--ref-accent); }
.column.enh-col { border-top: 4px solid var(--enh-accent); }

.column-header {
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: #151d2f;
}

.column-title {
  font-size: 0.92rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 8px;
}

.column.ahaana-col .column-title { color: var(--ahaana-accent); }
.column.ref-col .column-title { color: var(--ref-accent); }
.column.enh-col .column-title { color: var(--enh-accent); }

.cards-scroll-area {
  flex: 1;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  padding: 12px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

/* Card Box */
.card-box {
  background-color: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 14px;
  position: relative;
  transition: transform 0.1s ease, box-shadow 0.15s ease;
  user-select: text;
}

.card-box:active {
  transform: scale(0.99);
}

.card-box.ahaana-card { border-left: 4px solid var(--ahaana-accent); }
.card-box.ref-card { border-left: 4px solid var(--ref-accent); }
.card-box.enh-card { border-left: 4px solid var(--enh-accent); background-color: #0f1c30; border-color: #1e3a8a; }

.card-term {
  font-weight: 700;
  font-size: 0.92rem;
  color: #fff;
  margin-bottom: 8px;
  line-height: 1.4;
}

.card-definition {
  font-size: 0.85rem;
  color: #cbd5e1;
  white-space: pre-wrap;
  line-height: 1.5;
}

.examiner-alert {
  background-color: var(--warning-bg);
  border: 1px solid var(--warning-border);
  color: var(--warning-text);
  border-radius: 8px;
  padding: 8px 12px;
  margin-top: 10px;
  font-size: 0.8rem;
  display: flex;
  gap: 6px;
  align-items: flex-start;
}

.keyword-tags {
  margin-top: 8px;
  display: flex;
  flex-wrap: wrap;
  gap: 4px;
}

.kw-tag {
  background-color: rgba(52, 211, 153, 0.15);
  color: #6ee7b7;
  border: 1px solid rgba(52, 211, 153, 0.3);
  font-size: 0.7rem;
  padding: 3px 8px;
  border-radius: 4px;
}

.card-actions {
  margin-top: 12px;
  padding-top: 10px;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  display: flex;
  justify-content: flex-end;
  gap: 8px;
}

.action-btn {
  background: var(--bg-subtle);
  border: 1px solid var(--border);
  color: var(--text-primary);
  font-size: 0.78rem;
  padding: 6px 12px;
  border-radius: 6px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 4px;
  min-height: 34px;
}
.action-btn:hover { background-color: var(--border); }
.action-btn.adopt {
  background: rgba(52, 211, 153, 0.2);
  border-color: rgba(52, 211, 153, 0.4);
  color: #6ee7b7;
  font-weight: 600;
}
.action-btn.adopt:hover { background: rgba(52, 211, 153, 0.3); }

.empty-placeholder {
  text-align: center;
  padding: 40px 20px;
  color: var(--text-muted);
  font-size: 0.88rem;
}

/* Modals */
.modal-overlay {
  display: none;
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: rgba(0, 0, 0, 0.75);
  z-index: 1000;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(5px);
}
.modal-overlay.active { display: flex; }

.modal-content {
  background: #151d2f;
  border: 1px solid var(--border);
  border-radius: 16px;
  width: 90%;
  max-width: 650px;
  max-height: 85vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  box-shadow: 0 24px 48px rgba(0, 0, 0, 0.6);
}

.modal-header {
  padding: 16px 20px;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.modal-header h3 { font-size: 1.15rem; color: #fff; }

.modal-body {
  padding: 20px;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  flex: 1;
}

.modal-footer {
  padding: 14px 20px;
  border-top: 1px solid var(--border);
  display: flex;
  justify-content: flex-end;
  gap: 10px;
  background-color: #0e1422;
}

.form-group {
  margin-bottom: 16px;
}
.form-group label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text-secondary);
}
.form-input, .form-textarea {
  width: 100%;
  background: #090d16;
  border: 1px solid var(--border);
  padding: 12px;
  border-radius: 8px;
  color: #fff;
  font-size: 0.9rem;
  outline: none;
  font-family: inherit;
}
.form-textarea { min-height: 120px; resize: vertical; }
.form-input:focus, .form-textarea:focus { border-color: var(--subject-accent); }

/* Export textarea */
.export-preview {
  width: 100%;
  height: 240px;
  background: #090d16;
  border: 1px solid var(--border);
  color: #38bdf8;
  font-family: "SFMono-Regular", Consolas, Menlo, monospace;
  font-size: 0.82rem;
  padding: 12px;
  border-radius: 8px;
  white-space: pre;
  overflow: auto;
}

/* Cloud Sync Status Indicator */
.sync-indicator {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 0.75rem;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: 9999px;
  background-color: var(--bg-card);
  border: 1px solid var(--border);
}
.sync-indicator.synced { color: #34d399; border-color: rgba(52, 211, 153, 0.4); }
.sync-indicator.syncing { color: #38bdf8; border-color: rgba(56, 189, 248, 0.4); }
.sync-indicator.offline { color: #fbbf24; border-color: rgba(251, 191, 36, 0.4); }

.sync-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: currentColor;
}
.sync-indicator.syncing .sync-dot {
  animation: pulse 1s infinite;
}

@keyframes pulse {
  0% { opacity: 0.3; transform: scale(0.8); }
  50% { opacity: 1; transform: scale(1.2); }
  100% { opacity: 0.3; transform: scale(0.8); }
}

/* Floating AI Tutor Button */
.floating-ai-btn {
  position: fixed;
  bottom: 24px;
  right: 24px;
  background: var(--subject-gradient);
  color: #fff;
  border: none;
  border-radius: 9999px;
  padding: 12px 20px;
  font-size: 0.95rem;
  font-weight: 700;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.5);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 8px;
  z-index: 100;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}
.floating-ai-btn:active {
  transform: scale(0.96);
}

/* AI Tutor Drawer */
.ai-drawer {
  position: fixed;
  top: 0;
  right: -420px;
  width: 400px;
  height: 100vh;
  background-color: #111827;
  border-left: 1px solid var(--border);
  box-shadow: -10px 0 30px rgba(0, 0, 0, 0.6);
  z-index: 1000;
  display: flex;
  flex-direction: column;
  transition: right 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}
.ai-drawer.open {
  right: 0;
}

.ai-drawer-header {
  padding: 16px 20px;
  background-color: #151d2f;
  border-bottom: 1px solid var(--border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.ai-drawer-header h3 {
  font-size: 1.05rem;
  color: #fff;
  display: flex;
  align-items: center;
  gap: 8px;
}

.ai-messages {
  flex: 1;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  padding: 16px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.ai-msg {
  padding: 12px 14px;
  border-radius: 10px;
  font-size: 0.86rem;
  line-height: 1.5;
  user-select: text;
}
.ai-msg.user {
  background-color: var(--bg-subtle);
  color: #fff;
  align-self: flex-end;
  max-width: 85%;
}
.ai-msg.bot {
  background-color: #172554;
  border: 1px solid #1e40af;
  color: #e0f2fe;
  align-self: flex-start;
  max-width: 95%;
}

.ai-quick-chips {
  display: flex;
  gap: 6px;
  padding: 8px 16px;
  overflow-x: auto;
  background-color: rgba(0, 0, 0, 0.2);
  border-top: 1px solid var(--border);
}
.ai-chip {
  background: var(--bg-card);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  font-size: 0.72rem;
  padding: 4px 8px;
  border-radius: 9999px;
  white-space: nowrap;
  cursor: pointer;
}
.ai-chip:hover {
  color: #fff;
  border-color: var(--subject-accent);
}

.ai-input-bar {
  padding: 12px 16px;
  background-color: #151d2f;
  border-top: 1px solid var(--border);
  display: flex;
  gap: 8px;
}
.ai-input {
  flex: 1;
  background-color: #090d16;
  border: 1px solid var(--border);
  padding: 10px 12px;
  border-radius: 8px;
  color: #fff;
  font-size: 0.85rem;
  outline: none;
}
.ai-input:focus {
  border-color: var(--subject-accent);
}

.btn-ai-enhance {
  background: linear-gradient(135deg, #a855f7, #7c3aed);
  color: white;
  padding: 6px 12px;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.btn-ai-enhance:hover {
  filter: brightness(1.15);
}