/* ==========================================================================
   Biology Practice System - Mobile-First Academic Stylesheet
   Strictly: No emoji, No icons, No decorative shimmer/glow, High Performance
   Supports: Light/Dark Theme, Animated Bottom Drawer, Page/Question Mode
   ========================================================================== */

:root {
  /* Dynamic User Preferences */
  --user-font-size: 16px;
  --user-line-height: 1.6;
  --user-spacing: 16px;

  /* Color Palette - Light Theme (Default) */
  --bg-app: #f8fafc;
  --bg-surface: #ffffff;
  --bg-muted: #f1f5f9;
  --bg-subtle: #e2e8f0;
  
  --text-main: #0f172a;
  --text-secondary: #334155;
  --text-muted: #64748b;
  --text-inverse: #ffffff;
  
  --border-subtle: #e2e8f0;
  --border-main: #cbd5e1;
  --border-focus: #2563eb;
  
  --color-primary: #1e3a8a;
  --color-primary-hover: #172554;
  --color-accent: #0284c7;
  
  --color-success: #15803d;
  --color-success-bg: #dcfce7;
  --color-danger: #b91c1c;
  --color-danger-bg: #fee2e2;
  --color-warning: #b45309;
  --color-warning-bg: #fef3c7;

  --nav-height: 60px;
  --header-height: 94px;
  --font-family: 'SolaimanLipi', 'Hind Siliguri', 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'Consolas', 'Courier New', monospace;
}

/* Dark Theme */
[data-theme="dark"] {
  --bg-app: #090d16;
  --bg-surface: #131b2e;
  --bg-muted: #1e293b;
  --bg-subtle: #334155;

  --text-main: #f8fafc;
  --text-secondary: #cbd5e1;
  --text-muted: #94a3b8;
  --text-inverse: #090d16;

  --border-subtle: #1e293b;
  --border-main: #334155;
  --border-focus: #38bdf8;

  --color-primary: #38bdf8;
  --color-primary-hover: #7dd3fc;
  --color-accent: #0284c7;

  --color-success: #22c55e;
  --color-success-bg: #052e16;
  --color-danger: #ef4444;
  --color-danger-bg: #450a0a;
  --color-warning: #f59e0b;
  --color-warning-bg: #451a03;
}

/* Base Reset */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  height: 100%;
}

body {
  font-family: var(--font-family);
  background-color: var(--bg-app);
  color: var(--text-main);
  line-height: var(--user-line-height);
  font-size: var(--user-font-size);
  min-height: 100dvh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* App Shell */
.app-container {
  display: flex;
  flex-direction: column;
  min-height: 100dvh;
  position: relative;
}

/* Compact Mobile-First Header */
.app-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background-color: var(--bg-surface);
  border-bottom: 1px solid var(--border-main);
  padding: 8px 14px;
}

.header-row-primary {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 8px;
}

.header-brand {
  display: flex;
  flex-direction: column;
  min-width: 0;
}

.app-title {
  font-size: 15px;
  font-weight: 700;
  color: var(--color-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.active-chapter-indicator {
  font-size: 11px;
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 170px;
}

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

.timer-badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  background-color: var(--bg-muted);
  border: 1px solid var(--border-main);
  border-radius: 4px;
  padding: 4px 8px;
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  color: var(--text-main);
}

.timer-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background-color: var(--color-success);
}

/* Quick Metrics Strip */
.header-row-metrics {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-top: 6px;
  padding-top: 6px;
  border-top: 1px solid var(--border-subtle);
  font-size: 11px;
}

.metric-item {
  display: inline-flex;
  gap: 3px;
}

.metric-lbl {
  color: var(--text-muted);
}

.metric-val {
  font-weight: 700;
  font-family: var(--font-mono);
}

.mistake-val {
  color: var(--color-danger);
}

.progress-bar-wrap {
  flex: 1;
  height: 4px;
  background-color: var(--bg-subtle);
  border-radius: 2px;
  overflow: hidden;
  margin-left: auto;
}

.progress-bar-fill {
  height: 100%;
  background-color: var(--color-primary);
  width: 0%;
  transition: width 0.2s ease;
}

/* Buttons */
.btn {
  font-family: inherit;
  font-size: 13px;
  font-weight: 600;
  padding: 8px 14px;
  border-radius: 6px;
  border: 1px solid transparent;
  cursor: pointer;
  white-space: nowrap;
  background: none;
  min-height: 38px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.btn-sm {
  padding: 4px 10px;
  font-size: 12px;
  min-height: 30px;
  border-radius: 4px;
}

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

[data-theme="dark"] .btn-primary {
  color: #090d16;
}

.btn-primary:hover:not(:disabled) {
  opacity: 0.92;
}

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

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

.btn-outline {
  border-color: var(--border-main);
  color: var(--text-secondary);
}

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

.btn-danger {
  background-color: var(--color-danger);
  color: #ffffff;
  border-color: var(--color-danger);
}

.btn-nav {
  flex: 1;
  max-width: 130px;
  background-color: var(--bg-surface);
  color: var(--text-main);
  border: 1px solid var(--border-main);
  font-weight: 700;
}

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

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn-text-link {
  background: none;
  border: none;
  color: var(--color-accent);
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  text-decoration: underline;
  padding: 2px 4px;
}

/* Main Practice Canvas */
.practice-main {
  flex: 1;
  display: flex;
  flex-direction: column;
  padding-bottom: calc(var(--nav-height) + env(safe-area-inset-bottom) + 16px);
}

.questions-viewport {
  width: 100%;
  max-width: 780px;
  margin: 0 auto;
  padding: var(--user-spacing) 14px;
}

/* Question Mode Card & Page Mode Items */
.question-card {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  border-radius: 8px;
  padding: var(--user-spacing);
  margin-bottom: var(--user-spacing);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
}

.page-mode-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 10px;
  margin-bottom: 14px;
  border-bottom: 1px solid var(--border-main);
  font-size: 13px;
  color: var(--text-muted);
}

.page-mode-header strong {
  color: var(--text-main);
}

/* ==========================================================================
   Scroll Mode (Continuous Single-Page Scrolling for All Questions)
   ========================================================================== */
.scroll-mode-container {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.scroll-mode-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  padding: 10px 14px;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  border-radius: 8px;
  margin-bottom: 4px;
}

.scroll-header-info {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.scroll-mode-badge {
  font-size: 13px;
  font-weight: 700;
  color: var(--color-accent);
}

.scroll-count-tag {
  font-size: 12px;
  color: var(--text-muted);
  background: var(--bg-muted);
  padding: 2px 8px;
  border-radius: 4px;
}

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

.scroll-cards-container {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.scroll-sentinel {
  padding: 14px 8px 30px;
  text-align: center;
}

.scroll-loading-more {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  border-radius: 20px;
  font-size: 12px;
  color: var(--text-secondary);
  box-shadow: 0 1px 4px rgba(0,0,0,0.04);
}

.scroll-end-banner {
  padding: 12px;
  background-color: var(--color-success-bg);
  border: 1px solid rgba(16, 185, 129, 0.3);
  border-radius: 8px;
  font-size: 12.5px;
  font-weight: 600;
  color: var(--color-success);
}

.pulse-focus {
  animation: cardPulse 1.2s ease-out;
}

@keyframes cardPulse {
  0% { box-shadow: 0 0 0 0 rgba(2, 132, 199, 0.6); }
  50% { box-shadow: 0 0 0 8px rgba(2, 132, 199, 0.2); }
  100% { box-shadow: 0 0 0 0 rgba(2, 132, 199, 0); }
}

.btn-scroll-toggle {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  font-weight: 600;
}

.q-meta-line {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
  margin-bottom: 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-subtle);
}

.q-tags {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.tag {
  font-size: 11px;
  font-weight: 600;
  padding: 2px 7px;
  border-radius: 4px;
  text-transform: uppercase;
}

.tag-subject {
  background-color: #e0e7ff;
  color: #3730a3;
}

[data-theme="dark"] .tag-subject {
  background-color: #312e81;
  color: #e0e7ff;
}

.tag-chapter {
  background-color: var(--bg-muted);
  color: var(--text-muted);
  border: 1px solid var(--border-main);
}

.tag-type {
  background-color: var(--color-warning-bg);
  color: var(--color-warning);
}

.q-number-label {
  font-size: 13px;
  font-weight: 700;
  color: var(--text-muted);
}

.q-number-label strong {
  color: var(--text-main);
}

/* Question Text Content */
.q-content {
  font-size: var(--user-font-size);
  line-height: var(--user-line-height);
  font-weight: 500;
  color: var(--text-main);
  margin-bottom: var(--user-spacing);
  white-space: pre-wrap;
  word-break: break-word;
}

/* Options Container */
.q-options-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: var(--user-spacing);
}

.opt-item {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  padding: 10px 14px;
  background-color: var(--bg-surface);
  border: 1.5px solid var(--border-main);
  border-radius: 6px;
  cursor: pointer;
  min-height: 44px;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}

.opt-item:hover {
  border-color: var(--border-focus);
}

.opt-item.selected {
  border-color: var(--color-primary);
  background-color: var(--bg-muted);
}

.opt-item.correct {
  border-color: var(--color-success);
  background-color: var(--color-success-bg);
}

.opt-item.incorrect {
  border-color: var(--color-danger);
  background-color: var(--color-danger-bg);
}

.opt-badge {
  font-weight: 700;
  width: 24px;
  height: 24px;
  line-height: 24px;
  text-align: center;
  background-color: var(--bg-muted);
  border-radius: 50%;
  font-size: 13px;
  color: var(--text-secondary);
  flex-shrink: 0;
}

.opt-item.selected .opt-badge {
  background-color: var(--color-primary);
  color: var(--text-inverse);
}

.opt-item.correct .opt-badge {
  background-color: var(--color-success);
  color: #ffffff;
}

.opt-item.incorrect .opt-badge {
  background-color: var(--color-danger);
  color: #ffffff;
}

.opt-body {
  flex: 1;
  font-size: var(--user-font-size);
  line-height: 1.5;
}

/* Written Answer Form */
.written-area {
  margin-bottom: var(--user-spacing);
}

.written-textarea {
  width: 100%;
  min-height: 90px;
  padding: 10px;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  border-radius: 6px;
  font-family: inherit;
  font-size: var(--user-font-size);
  color: var(--text-main);
  outline: none;
}

.written-textarea:focus {
  border-color: var(--border-focus);
}

/* Action Strip */
.q-action-strip {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 12px;
}

/* Revealed Answer Box */
.q-revealed-box {
  background-color: var(--bg-muted);
  border: 1px solid var(--border-main);
  border-left: 4px solid var(--color-success);
  border-radius: 4px;
  padding: 12px 14px;
  margin-top: 10px;
  font-size: var(--user-font-size);
}

.revealed-ans-line {
  font-weight: 700;
  color: var(--color-success);
  margin-bottom: 6px;
}

.revealed-exp-line {
  font-size: calc(var(--user-font-size) - 1px);
  line-height: var(--user-line-height);
  color: var(--text-main);
  white-space: pre-wrap;
}

/* Inline Clean AI Explanation Panel */
.ai-inline-container {
  margin-top: 14px;
  border-top: 1px dashed var(--border-main);
  padding-top: 12px;
}

.ai-inline-box {
  background-color: var(--bg-muted);
  border: 1px solid var(--border-main);
  border-radius: 6px;
  padding: 14px;
  margin-top: 8px;
  font-size: var(--user-font-size);
  line-height: var(--user-line-height);
}

.ai-box-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-bottom: 8px;
  margin-bottom: 10px;
  border-bottom: 1px solid var(--border-subtle);
  font-size: 13px;
  font-weight: 700;
  color: var(--color-primary);
}

.ai-loading-state {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--text-muted);
  font-size: 13px;
  padding: 10px 0;
}

.ai-pulse-dot {
  width: 8px;
  height: 8px;
  background-color: var(--color-primary);
  border-radius: 50%;
  animation: pulse 1s infinite alternate;
}

@keyframes pulse {
  from { opacity: 0.3; transform: scale(0.85); }
  to { opacity: 1; transform: scale(1.15); }
}

.ai-clean-text {
  display: flex;
  flex-direction: column;
  gap: 10px;
  font-size: var(--user-font-size);
  line-height: var(--user-line-height);
  color: var(--text-main);
  word-break: break-word;
}

.ai-clean-text p,
.ai-clean-text .ai-para {
  margin: 0;
  line-height: 1.65;
}

.ai-clean-text strong {
  font-weight: 700;
  color: var(--color-primary);
}

[data-theme="dark"] .ai-clean-text strong {
  color: #38bdf8;
}

.ai-clean-text .ai-heading {
  font-size: calc(var(--user-font-size) + 0.5px);
  font-weight: 700;
  color: var(--color-primary);
  margin-top: 6px;
  margin-bottom: 2px;
  border-bottom: 1px dashed var(--border-subtle);
  padding-bottom: 3px;
}

[data-theme="dark"] .ai-clean-text .ai-heading {
  color: #38bdf8;
}

.ai-list-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin: 4px 0;
}

.ai-bullet-item {
  display: flex;
  align-items: flex-start;
  gap: 8px;
  line-height: 1.55;
}

.ai-bullet-item .bullet-dot {
  color: var(--color-accent);
  font-weight: 700;
  flex-shrink: 0;
  line-height: 1.4;
}

/* Bottom Sticky Navigation Bar */
.bottom-nav-bar {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: calc(var(--nav-height) + env(safe-area-inset-bottom));
  padding-bottom: env(safe-area-inset-bottom);
  background-color: var(--bg-surface);
  border-top: 1px solid var(--border-main);
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-left: 14px;
  padding-right: 14px;
  z-index: 40;
}

.nav-indicator-box {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.nav-position-text {
  font-size: 12px;
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--text-main);
}

/* Animated Bottom Drawer (Mobile) */
.drawer-backdrop {
  position: fixed;
  inset: 0;
  background-color: rgba(0, 0, 0, 0.5);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s ease;
  z-index: 999;
}

.drawer-backdrop.active {
  opacity: 1;
  pointer-events: auto;
}

.customization-drawer {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  max-height: 88dvh;
  background-color: var(--bg-surface);
  border-top: 1px solid var(--border-main);
  border-radius: 18px 18px 0 0;
  transform: translateY(100%);
  transition: transform 0.22s cubic-bezier(0.16, 1, 0.3, 1);
  z-index: 1000;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.customization-drawer.open {
  transform: translateY(0);
}

.drawer-drag-handle {
  width: 40px;
  height: 4px;
  background-color: var(--border-main);
  border-radius: 2px;
  margin: 10px auto 4px auto;
  flex-shrink: 0;
}

.drawer-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 18px;
  border-bottom: 1px solid var(--border-subtle);
  flex-shrink: 0;
}

.drawer-title {
  font-size: 15px;
  font-weight: 700;
  color: var(--color-primary);
}

.drawer-content {
  flex: 1;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  padding: 16px 18px calc(24px + env(safe-area-inset-bottom));
  display: flex;
  flex-direction: column;
  gap: 18px;
}

.drawer-section {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.section-title {
  font-size: 13px;
  font-weight: 700;
  color: var(--text-secondary);
}

.section-hint {
  font-size: 11px;
  color: var(--text-muted);
}

/* Custom Segmented Controls */
.segmented-control {
  display: flex;
  background-color: var(--bg-muted);
  border: 1px solid var(--border-main);
  border-radius: 6px;
  padding: 3px;
  gap: 3px;
}

.segment-btn {
  flex: 1;
  background: none;
  border: none;
  padding: 8px 10px;
  font-size: 12px;
  font-weight: 600;
  color: var(--text-secondary);
  border-radius: 4px;
  cursor: pointer;
  transition: background-color 0.15s ease, color 0.15s ease;
}

.segment-btn.active {
  background-color: var(--bg-surface);
  color: var(--text-main);
  font-weight: 700;
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.08);
}

/* Chip Groups */
.chip-group {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.chip-btn {
  background-color: var(--bg-muted);
  border: 1px solid var(--border-main);
  color: var(--text-secondary);
  padding: 6px 12px;
  border-radius: 16px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s ease;
}

.chip-btn.active {
  background-color: var(--color-primary);
  border-color: var(--color-primary);
  color: var(--text-inverse);
}

[data-theme="dark"] .chip-btn.active {
  color: #090d16;
}

.checkbox-setting-label {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
}

.drawer-select {
  width: 100%;
  padding: 8px 10px;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  border-radius: 6px;
  font-family: inherit;
  font-size: 13px;
  color: var(--text-main);
  outline: none;
}

/* Question Palette Modal */
.question-palette-modal {
  position: fixed;
  left: 14px;
  right: 14px;
  bottom: calc(var(--nav-height) + env(safe-area-inset-bottom) + 12px);
  max-height: 70dvh;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  border-radius: 10px;
  padding: 14px;
  z-index: 1001;
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.15);
  display: flex;
  flex-direction: column;
}

.palette-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-subtle);
  margin-bottom: 10px;
}

.palette-title {
  font-size: 14px;
  font-weight: 700;
}

.palette-legend {
  display: flex;
  gap: 8px;
  font-size: 11px;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 3px;
}

.legend-box {
  width: 10px;
  height: 10px;
  border-radius: 2px;
}

.legend-box.current { background-color: var(--color-primary); }
.legend-box.answered { background-color: var(--color-success); }
.legend-box.mistake { background-color: var(--color-danger); }
.legend-box.review { background-color: var(--color-warning); }

.palette-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(40px, 1fr));
  gap: 6px;
  overflow-y: auto;
  max-height: 260px;
  padding: 4px;
}

.palette-item {
  height: 36px;
  border: 1px solid var(--border-main);
  background-color: var(--bg-surface);
  color: var(--text-main);
  font-size: 12px;
  font-weight: 600;
  border-radius: 4px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
}

.palette-item.current {
  background-color: var(--color-primary);
  color: var(--text-inverse);
  border-color: var(--color-primary);
}

[data-theme="dark"] .palette-item.current {
  color: #090d16;
}

.palette-item.answered {
  background-color: var(--color-success);
  color: #ffffff;
  border-color: var(--color-success);
}

.palette-item.mistake {
  background-color: var(--color-danger);
  color: #ffffff;
  border-color: var(--color-danger);
}

.palette-item.review {
  background-color: var(--color-warning);
  color: #ffffff;
  border-color: var(--color-warning);
}

/* Desktop View Adaptations */
@media (min-width: 768px) {
  .customization-drawer {
    left: 50%;
    right: auto;
    bottom: auto;
    top: 50%;
    transform: translate(-50%, -50%) scale(0.95);
    opacity: 0;
    pointer-events: none;
    width: 480px;
    max-height: 82dvh;
    border-radius: 12px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.2);
    transition: transform 0.2s ease, opacity 0.2s ease;
  }

  .customization-drawer.open {
    transform: translate(-50%, -50%) scale(1);
    opacity: 1;
    pointer-events: auto;
  }

  .drawer-drag-handle {
    display: none;
  }

  .question-palette-modal {
    left: 50%;
    right: auto;
    bottom: auto;
    top: 50%;
    transform: translate(-50%, -50%);
    width: 480px;
  }
}

/* Accessibility: Reduced Motion */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ==========================================================================
   AI Custom Query & Previous Explanations Panel
   ========================================================================== */
.ai-custom-section {
  margin-top: 10px;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.ai-custom-input-row {
  display: flex;
  gap: 8px;
  align-items: center;
}

.ai-custom-input {
  flex: 1;
  padding: 8px 12px;
  font-size: 13px;
  border: 1px solid var(--border-main);
  border-radius: 6px;
  background-color: var(--bg-surface);
  color: var(--text-main);
  outline: none;
}

.ai-custom-input:focus {
  border-color: var(--border-focus);
}

.ai-custom-response-box {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  border-left: 3px solid var(--color-accent);
  border-radius: 6px;
  padding: 12px;
  font-size: calc(var(--user-font-size) - 1px);
  line-height: var(--user-line-height);
  color: var(--text-main);
}

.ai-history-toggle-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 8px;
}

.ai-history-container {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px dashed var(--border-subtle);
}

.ai-history-item {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: 6px;
  padding: 10px 12px;
  font-size: calc(var(--user-font-size) - 1px);
}

.ai-history-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 6px;
  font-size: 11px;
  color: var(--text-muted);
}

.ai-history-query-badge {
  font-weight: 600;
  color: var(--color-primary);
}

.shortcut-tag {
  font-size: 10px;
  opacity: 0.7;
  font-family: var(--font-mono);
  margin-left: 4px;
}

/* ==========================================================================
   Suggestion Modal (.md Viewer) & AI Persona Styles
   ========================================================================== */
.suggestion-modal {
  position: fixed;
  left: 12px;
  right: 12px;
  bottom: calc(var(--nav-height) + env(safe-area-inset-bottom) + 8px);
  top: 40px;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  border-radius: 12px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.25);
  z-index: 1001;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.suggestion-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border-subtle);
  background-color: var(--bg-muted);
  flex-wrap: wrap;
  gap: 8px;
}

.suggestion-title-wrap {
  display: flex;
  align-items: center;
  gap: 8px;
}

.suggestion-title {
  font-size: 14px;
  font-weight: 700;
  color: var(--color-primary);
}

.suggestion-actions {
  display: flex;
  gap: 6px;
}

.suggestion-body {
  flex: 1;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  padding: 18px;
  font-size: 14px;
  line-height: 1.7;
  color: var(--text-main);
  white-space: pre-wrap;
  word-break: break-word;
}

.suggestion-body h1, .suggestion-body h2, .suggestion-body h3 {
  color: var(--color-primary);
  margin-top: 14px;
  margin-bottom: 8px;
}

.suggestion-body ul, .suggestion-body ol {
  margin-left: 20px;
  margin-bottom: 12px;
}

.suggestion-body table {
  width: 100%;
  border-collapse: collapse;
  margin: 12px 0;
  font-size: 13px;
}

.suggestion-body th, .suggestion-body td {
  border: 1px solid var(--border-main);
  padding: 8px 10px;
  text-align: left;
}

.suggestion-body th {
  background-color: var(--bg-muted);
  font-weight: 700;
}

/* AI Persona Quick Selector Strip */
.persona-selector-strip {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-bottom: 10px;
  overflow-x: auto;
  padding-bottom: 4px;
}

.persona-label {
  font-size: 11px;
  font-weight: 700;
  color: var(--text-muted);
  white-space: nowrap;
}

.persona-pill {
  padding: 3px 8px;
  font-size: 11px;
  border-radius: 12px;
  border: 1px solid var(--border-main);
  background-color: var(--bg-muted);
  color: var(--text-secondary);
  cursor: pointer;
  white-space: nowrap;
}

.persona-pill.active {
  background-color: var(--color-primary);
  color: var(--text-inverse);
  border-color: var(--color-primary);
}

[data-theme="dark"] .persona-pill.active {
  color: #090d16;
}

@media (min-width: 768px) {
  .suggestion-modal {
    left: 50%;
    right: auto;
    top: 50%;
    bottom: auto;
    transform: translate(-50%, -50%);
    width: 680px;
    height: 80vh;
  }
}

/* ==========================================================================
   AI Question Review & Auto-Correction Panel
   ========================================================================== */
.ai-audit-panel {
  margin-top: 12px;
  border-radius: 8px;
  border: 1px solid var(--border-main);
  background-color: var(--bg-surface);
  padding: 14px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.ai-audit-panel.audit-valid {
  border-left: 4px solid var(--color-success);
  background-color: var(--color-success-bg);
}

.ai-audit-panel.audit-invalid {
  border-left: 4px solid var(--color-warning);
  background-color: var(--color-warning-bg);
}

.audit-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
  border-bottom: 1px solid rgba(0, 0, 0, 0.08);
  padding-bottom: 8px;
}

.audit-status-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  font-weight: 700;
  padding: 2px 10px;
  border-radius: 12px;
}

.audit-status-badge.valid {
  background-color: var(--color-success);
  color: #ffffff;
}

.audit-status-badge.invalid {
  background-color: var(--color-warning);
  color: #ffffff;
}

.audit-meta-text {
  font-size: 11px;
  color: var(--text-muted);
}

.audit-summary {
  font-size: calc(var(--user-font-size) - 1px);
  line-height: var(--user-line-height);
  color: var(--text-main);
}

.audit-diff-card {
  background-color: var(--bg-surface);
  border: 1px dashed var(--border-main);
  border-radius: 6px;
  padding: 10px 12px;
  font-size: calc(var(--user-font-size) - 1px);
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.audit-answer-diff {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  font-weight: 700;
  font-size: 13px;
}

.audit-answer-diff .diff-old {
  color: var(--color-danger);
  text-decoration: line-through;
}

.audit-answer-diff .diff-new {
  color: var(--color-success);
}

.audit-tip-box {
  background-color: var(--bg-muted);
  border-left: 3px solid var(--color-accent);
  padding: 8px 12px;
  border-radius: 4px;
  font-size: 12px;
  color: var(--text-secondary);
}

.tag-corrected {
  background-color: var(--color-success);
  color: #ffffff;
  font-weight: 700;
}

.tag-na-warning {
  background-color: #fef3c7;
  color: #b45309;
  border: 1px solid #fde68a;
  font-weight: 600;
}

.ans-badge-na {
  color: #d97706;
  font-weight: 700;
  background: #fef3c7;
  padding: 1px 6px;
  border-radius: 4px;
}

.btn-quick-resolve {
  margin-left: 10px;
  background: #fffbeb;
  color: #b45309;
  border: 1px solid #f59e0b;
  border-radius: 4px;
  padding: 3px 8px;
  font-size: 11px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.15s ease;
}

.btn-quick-resolve:hover {
  background: #fef3c7;
  color: #92400e;
}

.revealed-na-hint {
  font-size: 11.5px;
  color: #b45309;
  background-color: #fffbeb;
  border-left: 3px solid #f59e0b;
  padding: 6px 10px;
  margin-top: 6px;
  border-radius: 4px;
  line-height: 1.4;
}

/* Auto-Save & Accept System */
.audit-autosave-box {
  background-color: rgba(16, 185, 129, 0.08);
  border: 1px solid rgba(16, 185, 129, 0.4);
  border-radius: 8px;
  padding: 12px 14px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.audit-autosave-title {
  display: flex;
  align-items: flex-start;
  gap: 10px;
}

.audit-check-circle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background-color: var(--color-success);
  color: #ffffff;
  font-size: 13px;
  font-weight: 800;
  flex-shrink: 0;
}

.audit-autosave-sub {
  font-size: 12.5px;
  margin-top: 3px;
  color: var(--text-secondary);
}

.text-success {
  color: var(--color-success);
}

.audit-accept-row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 10px;
  padding-top: 4px;
  border-top: 1px dashed rgba(16, 185, 129, 0.25);
}

.btn-accept-confirmed {
  background-color: #059669;
  color: #ffffff;
  border: none;
  border-radius: 6px;
  padding: 6px 14px;
  font-size: 12px;
  font-weight: 700;
  cursor: default;
  display: inline-flex;
  align-items: center;
  gap: 5px;
}

.btn-accept-action {
  background-color: var(--color-success);
  color: #ffffff;
  border: none;
  border-radius: 6px;
  padding: 7px 14px;
  font-size: 12px;
  font-weight: 700;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 5px;
  transition: all 0.15s ease;
}

.btn-accept-action:hover {
  background-color: #059669;
}

.manual-override-group {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.manual-override-label {
  font-size: 11px;
  color: var(--text-muted);
}

.pill-group {
  display: inline-flex;
  gap: 4px;
}

.btn-pill-opt {
  padding: 3px 8px;
  font-size: 11px;
  font-weight: 700;
  border: 1px solid var(--border-main);
  background-color: var(--bg-surface);
  color: var(--text-main);
  border-radius: 4px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.btn-pill-opt:hover {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.btn-pill-opt.active {
  background-color: var(--color-success);
  border-color: var(--color-success);
  color: #ffffff;
}

.btn-apply-correction {
  background-color: var(--color-success);
  color: #ffffff;
  border: none;
  border-radius: 6px;
  padding: 8px 14px;
  font-size: 12px;
  font-weight: 700;
  cursor: pointer;
  align-self: flex-start;
  transition: opacity 0.15s ease;
}

.btn-apply-correction:hover {
  opacity: 0.9;
}

/* ==========================================================================
   Practice Format Switcher Card (Inside Customization Toggle Drawer)
   ========================================================================== */
.practice-format-section {
  background-color: var(--bg-hover);
  border: 1px solid var(--border-main);
  border-radius: var(--radius-md);
  padding: 12px 14px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

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

.status-pill {
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  padding: 2px 8px;
  border-radius: 999px;
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  color: var(--text-muted);
}

.status-pill.active {
  background-color: rgba(15, 118, 110, 0.12);
  color: var(--color-accent);
  border-color: rgba(15, 118, 110, 0.3);
}

.format-switcher-cards {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.format-card {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 10px 12px;
  border-radius: var(--radius-sm);
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  text-decoration: none;
  transition: all 0.16s ease;
  min-height: 52px;
}

.format-card:hover {
  border-color: var(--color-accent);
  background-color: var(--bg-active);
}

.format-card.active {
  background-color: var(--bg-surface);
  border: 2px solid var(--color-accent);
  box-shadow: 0 2px 6px rgba(15, 118, 110, 0.12);
}

.format-card-left {
  display: flex;
  align-items: center;
  gap: 10px;
}

.format-card-icon {
  width: 32px;
  height: 32px;
  border-radius: 8px;
  background-color: var(--bg-hover);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  flex-shrink: 0;
}

.format-card.active .format-card-icon {
  background-color: rgba(15, 118, 110, 0.15);
  color: var(--color-accent);
}

.format-card-meta {
  display: flex;
  flex-direction: column;
  gap: 1px;
}

.format-card-title {
  font-size: 13px;
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.3;
}

.format-card-sub {
  font-size: 11px;
  color: var(--text-muted);
  line-height: 1.2;
}

.format-active-tag {
  font-size: 10px;
  font-weight: 700;
  color: #ffffff;
  background-color: var(--color-accent);
  padding: 2px 8px;
  border-radius: 999px;
  flex-shrink: 0;
}

.format-switch-arrow {
  font-size: 15px;
  font-weight: 700;
  color: var(--text-muted);
  flex-shrink: 0;
  padding: 0 4px;
}

/* ==========================================================================
   Mobile-First Polish & Compact Question Canvas (Best Mobile Fix)
   ========================================================================== */
@media (max-width: 600px) {
  :root {
    --user-spacing: 8px !important;
  }

  .app-header {
    padding: 5px 8px;
  }

  .header-brand .app-title {
    font-size: 13.5px;
  }

  .active-chapter-indicator {
    max-width: 120px;
    font-size: 10px;
  }

  .timer-badge {
    padding: 2px 6px;
    font-size: 11.5px;
  }

  .header-row-metrics {
    gap: 6px;
    font-size: 10px;
    margin-top: 3px;
    padding-top: 3px;
  }

  .questions-viewport {
    padding: 6px 6px 72px 6px !important;
    max-width: 100%;
  }

  .question-card {
    border-radius: 8px !important;
    padding: 8px 10px !important; /* FIXED: Compact, comfortable padding, no wasted space */
    margin-bottom: 8px !important;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.03);
  }

  .q-meta-line {
    margin-bottom: 6px !important;
    padding-bottom: 5px !important;
    gap: 4px !important;
  }

  .tag {
    padding: 1px 5px !important;
    font-size: 9.5px !important;
  }

  .q-number-label {
    font-size: 11.5px !important;
  }

  .q-content {
    font-size: 15px !important;
    line-height: 1.58 !important;
    margin-bottom: 8px !important;
  }

  .q-options-list {
    gap: 5px !important;
    margin-bottom: 8px !important;
  }

  .opt-item {
    padding: 7px 9px !important;
    min-height: 38px !important;
    gap: 8px !important;
    border-radius: 6px !important;
  }

  .opt-badge {
    width: 20px !important;
    height: 20px !important;
    line-height: 20px !important;
    font-size: 11px !important;
  }

  .opt-text {
    font-size: 13.5px !important;
    line-height: 1.45 !important;
  }

  .q-actions-bar {
    margin-top: 6px !important;
    padding-top: 5px !important;
    gap: 4px !important;
  }

  .q-actions-bar .btn {
    padding: 5px 8px !important;
    font-size: 11px !important;
    min-height: 30px !important;
  }

  .ai-inline-container {
    margin-top: 6px !important;
    padding-top: 6px !important;
  }

  .persona-selector-strip {
    gap: 3px !important;
    margin-bottom: 6px !important;
  }

  .persona-pill {
    padding: 3px 7px !important;
    font-size: 10.5px !important;
  }

  .ai-inline-box {
    padding: 8px 10px !important;
    margin-top: 6px !important;
  }

  .ai-clean-text {
    gap: 8px !important;
  }

  .ai-custom-section {
    margin-top: 6px !important;
  }

  .ai-custom-input {
    padding: 6px 8px !important;
    font-size: 12.5px !important;
  }

  .customization-drawer {
    border-radius: 18px 18px 0 0;
    max-height: 90dvh;
  }

  .bottom-nav-bar {
    padding: 6px 10px calc(6px + env(safe-area-inset-bottom));
    min-height: 48px;
  }

  .btn-nav {
    padding: 7px 14px;
    font-size: 12.5px;
  }
}

/* ==========================================================================
   Colorful Biochemical Reactions & LaTeX Equations (Shatadhru AI)
   ========================================================================== */
.katex-display {
  background: linear-gradient(135deg, rgba(2, 132, 199, 0.06), rgba(16, 185, 129, 0.06));
  border: 1px solid rgba(2, 132, 199, 0.22);
  border-left: 4px solid var(--color-accent);
  border-radius: 8px;
  padding: 10px 14px;
  margin: 12px 0;
  overflow-x: auto;
  overflow-y: hidden;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.03);
}

[data-theme="dark"] .katex-display {
  background: linear-gradient(135deg, rgba(56, 189, 248, 0.08), rgba(52, 211, 153, 0.08));
  border-color: rgba(56, 189, 248, 0.3);
}

/* Vivid Colors for Biochemical Formulas */
.katex .mord.mathnormal {
  color: #0284c7;
  font-weight: 600;
}
[data-theme="dark"] .katex .mord.mathnormal {
  color: #38bdf8;
}

.katex .mrel {
  color: #10b981;
  font-weight: bold;
}
[data-theme="dark"] .katex .mrel {
  color: #34d399;
}

.katex .mbin {
  color: #f59e0b;
  font-weight: bold;
}

.katex .mord.mathrm {
  color: #0d9488;
  font-weight: 600;
}
[data-theme="dark"] .katex .mord.mathrm {
  color: #2dd4bf;
}

/* Suggestion Interactive Chat */
.suggestion-chat-container {
  margin-top: 14px;
  border-top: 1px solid var(--border-main);
  padding-top: 12px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.suggestion-chat-header {
  font-size: 13px;
  font-weight: 700;
  color: var(--color-primary);
  display: flex;
  align-items: center;
  gap: 6px;
}

[data-theme="dark"] .suggestion-chat-header {
  color: #38bdf8;
}

.suggestion-chat-thread {
  max-height: 220px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 8px;
  background-color: var(--bg-hover);
  border: 1px solid var(--border-subtle);
  border-radius: 8px;
}

.chat-message {
  font-size: 13px;
  line-height: 1.6;
  padding: 8px 12px;
  border-radius: 8px;
  word-break: break-word;
}

.chat-message.ai-message {
  background-color: var(--bg-surface);
  border: 1px solid var(--border-main);
  border-left: 3px solid var(--color-accent);
  color: var(--text-main);
}

.chat-message.user-message {
  background-color: rgba(2, 132, 199, 0.1);
  border: 1px solid rgba(2, 132, 199, 0.25);
  color: var(--text-main);
  align-self: flex-end;
}

.suggestion-chat-input-bar {
  display: flex;
  gap: 8px;
}

.suggestion-input {
  flex: 1;
  padding: 8px 12px;
  font-size: 13px;
  border-radius: 6px;
  border: 1.5px solid var(--border-main);
  background-color: var(--bg-surface);
  color: var(--text-main);
  outline: none;
}

.suggestion-input:focus {
  border-color: var(--color-accent);
}