@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Outfit:wght@400;500;600;700;800&display=swap');

/* ============================================================
   CSS Variables & Themes
   ============================================================ */
:root {
  /* Light Theme */
  --bg-primary: #f0f2f8;
  --bg-secondary: #ffffff;
  --bg-card: #ffffff;
  --bg-card-hover: #f8f9ff;
  --bg-input: #f5f6fa;
  --bg-overlay: rgba(0, 0, 0, 0.45);

  --text-primary: #1a1a2e;
  --text-secondary: #4a4a6a;
  --text-tertiary: #8888a8;
  --text-on-accent: #ffffff;

  --accent-primary: #6C63FF;
  --accent-secondary: #3B82F6;
  --accent-gradient: linear-gradient(135deg, #6C63FF 0%, #3B82F6 100%);
  --accent-gradient-hover: linear-gradient(135deg, #5b53ee 0%, #2b72e6 100%);
  --accent-soft: rgba(108, 99, 255, 0.1);
  --accent-soft-hover: rgba(108, 99, 255, 0.18);

  --success: #22c55e;
  --success-bg: rgba(34, 197, 94, 0.12);
  --error: #ef4444;
  --error-bg: rgba(239, 68, 68, 0.12);
  --warning: #f59e0b;
  --warning-bg: rgba(245, 158, 11, 0.12);
  --hint: #8b5cf6;
  --hint-bg: rgba(139, 92, 246, 0.12);

  --border: rgba(0, 0, 0, 0.08);
  --border-strong: rgba(0, 0, 0, 0.15);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.06);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.12);
  --shadow-xl: 0 16px 48px rgba(0, 0, 0, 0.16);

  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
}

[data-theme="dark"] {
  --bg-primary: #0f0f1a;
  --bg-secondary: #1a1a2e;
  --bg-card: #1e1e35;
  --bg-card-hover: #25254a;
  --bg-input: #16162b;
  --bg-overlay: rgba(0, 0, 0, 0.65);

  --text-primary: #e8e8f0;
  --text-secondary: #a0a0c0;
  --text-tertiary: #6a6a8a;

  --accent-soft: rgba(108, 99, 255, 0.15);
  --accent-soft-hover: rgba(108, 99, 255, 0.25);

  --success-bg: rgba(34, 197, 94, 0.15);
  --error-bg: rgba(239, 68, 68, 0.15);
  --warning-bg: rgba(245, 158, 11, 0.15);
  --hint-bg: rgba(139, 92, 246, 0.15);

  --border: rgba(255, 255, 255, 0.06);
  --border-strong: rgba(255, 255, 255, 0.12);
  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.2);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.4);
  --shadow-xl: 0 16px 48px rgba(0, 0, 0, 0.5);
}

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

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  overflow-x: hidden;
  transition: background var(--transition-normal), color var(--transition-normal);
  line-height: 1.6;
}

/* ============================================================
   Background Decoration
   ============================================================ */
.bg-decoration {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 0;
  overflow: hidden;
}

.bg-decoration .orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: 0.3;
  animation: orbFloat 20s ease-in-out infinite;
}

.bg-decoration .orb:nth-child(1) {
  width: 400px;
  height: 400px;
  background: var(--accent-primary);
  top: -100px;
  right: -100px;
  animation-delay: 0s;
}

.bg-decoration .orb:nth-child(2) {
  width: 300px;
  height: 300px;
  background: var(--accent-secondary);
  bottom: -50px;
  left: -50px;
  animation-delay: -7s;
}

.bg-decoration .orb:nth-child(3) {
  width: 200px;
  height: 200px;
  background: #8b5cf6;
  top: 50%;
  left: 50%;
  animation-delay: -14s;
}

[data-theme="dark"] .bg-decoration .orb {
  opacity: 0.15;
}

@keyframes orbFloat {
  0%, 100% { transform: translate(0, 0) scale(1); }
  25% { transform: translate(30px, -30px) scale(1.05); }
  50% { transform: translate(-20px, 20px) scale(0.95); }
  75% { transform: translate(15px, 10px) scale(1.02); }
}

/* ============================================================
   Layout
   ============================================================ */
.app-container {
  position: relative;
  z-index: 1;
  max-width: 720px;
  margin: 0 auto;
  padding: 20px;
  min-height: 100vh;
}

/* ============================================================
   Header
   ============================================================ */
.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 0;
  margin-bottom: 8px;
}

.app-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  text-decoration: none;
}

.app-logo .logo-icon {
  width: 40px;
  height: 40px;
  background: var(--accent-gradient);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  color: white;
  box-shadow: 0 4px 12px rgba(108, 99, 255, 0.3);
}

.app-logo .logo-text {
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  font-size: 1.3rem;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

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

/* Theme Toggle */
.theme-toggle {
  width: 44px;
  height: 44px;
  border: none;
  background: var(--bg-card);
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  color: var(--text-secondary);
  transition: all var(--transition-fast);
  border: 1px solid var(--border);
}

.theme-toggle:hover {
  background: var(--accent-soft);
  color: var(--accent-primary);
  transform: scale(1.05);
}

.theme-toggle:active {
  transform: scale(0.95);
}

/* ============================================================
   Views (Page Sections)
   ============================================================ */
.view {
  display: none;
  animation: fadeIn 0.4s ease;
}

.view.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes scaleIn {
  from { opacity: 0; transform: scale(0.92); }
  to { opacity: 1; transform: scale(1); }
}

/* ============================================================
   Home View
   ============================================================ */
.home-hero {
  text-align: center;
  padding: 40px 0 32px;
}

.home-hero .hero-emoji {
  font-size: 64px;
  margin-bottom: 16px;
  display: block;
  animation: bounceIn 0.6s ease;
}

@keyframes bounceIn {
  0% { transform: scale(0); }
  50% { transform: scale(1.15); }
  100% { transform: scale(1); }
}

.home-hero h1 {
  font-family: 'Outfit', sans-serif;
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 8px;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.home-hero .subtitle {
  color: var(--text-secondary);
  font-size: 1rem;
  font-weight: 400;
  max-width: 400px;
  margin: 0 auto;
}

/* Difficulty Selection */
.difficulty-section {
  margin: 32px 0;
}

.section-label {
  font-family: 'Outfit', sans-serif;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 1.5px;
  margin-bottom: 12px;
}

.difficulty-cards {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
}

.difficulty-card {
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px 16px;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.difficulty-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: var(--accent-gradient);
  opacity: 0;
  transition: opacity var(--transition-fast);
}

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

.difficulty-card.selected {
  border-color: var(--accent-primary);
  background: var(--accent-soft);
}

.difficulty-card.selected::before {
  opacity: 1;
}

.difficulty-card .card-icon {
  font-size: 32px;
  margin-bottom: 8px;
  display: block;
}

.difficulty-card .card-title {
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  font-size: 1.1rem;
  margin-bottom: 4px;
  color: var(--text-primary);
}

.difficulty-card .card-desc {
  font-size: 0.8rem;
  color: var(--text-tertiary);
}

/* Start Button */
.start-btn {
  width: 100%;
  padding: 16px;
  border: none;
  border-radius: var(--radius-lg);
  background: var(--accent-gradient);
  color: var(--text-on-accent);
  font-family: 'Outfit', sans-serif;
  font-size: 1.15rem;
  font-weight: 700;
  cursor: pointer;
  transition: all var(--transition-fast);
  box-shadow: 0 4px 16px rgba(108, 99, 255, 0.3);
  margin-top: 24px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}

.start-btn:hover {
  background: var(--accent-gradient-hover);
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(108, 99, 255, 0.4);
}

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

.start-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

/* Feature Cards (Home Menu) */
.feature-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 32px;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px 16px;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-align: center;
}

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

.feature-card .feature-icon {
  font-size: 28px;
  margin-bottom: 8px;
  display: block;
}

.feature-card .feature-title {
  font-family: 'Outfit', sans-serif;
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text-primary);
  margin-bottom: 2px;
}

.feature-card .feature-desc {
  font-size: 0.75rem;
  color: var(--text-tertiary);
}

/* Stats Row */
.stats-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin-top: 32px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.stat-item {
  text-align: center;
}

.stat-value {
  font-family: 'Outfit', sans-serif;
  font-size: 1.5rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-label {
  font-size: 0.75rem;
  color: var(--text-tertiary);
  margin-top: 2px;
}

/* ============================================================
   Quiz View
   ============================================================ */
.quiz-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 20px;
}

.quiz-back-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  border-radius: var(--radius-full);
  cursor: pointer;
  color: var(--text-secondary);
  font-size: 0.85rem;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.quiz-back-btn:hover {
  background: var(--error-bg);
  color: var(--error);
  border-color: var(--error);
}

.quiz-progress-info {
  font-family: 'Outfit', sans-serif;
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.quiz-progress-info span {
  color: var(--accent-primary);
  font-size: 1.1rem;
}

/* Progress Bar */
.progress-bar-wrapper {
  width: 100%;
  height: 6px;
  background: var(--bg-input);
  border-radius: var(--radius-full);
  margin-bottom: 28px;
  overflow: hidden;
}

.progress-bar-fill {
  height: 100%;
  background: var(--accent-gradient);
  border-radius: var(--radius-full);
  transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  min-width: 0;
}

/* Question Card */
.question-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  padding: 28px 24px;
  box-shadow: var(--shadow-md);
  animation: scaleIn 0.35s ease;
  margin-bottom: 20px;
}

.question-collocation {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--accent-soft);
  color: var(--accent-primary);
  padding: 6px 14px;
  border-radius: var(--radius-full);
  font-family: 'Outfit', sans-serif;
  font-weight: 600;
  font-size: 0.85rem;
  margin-bottom: 16px;
}

.question-meaning {
  color: var(--text-tertiary);
  font-size: 0.85rem;
  margin-bottom: 20px;
  padding-left: 2px;
}

.question-sentence {
  font-size: 1.15rem;
  line-height: 1.6;
  margin-bottom: 24px;
}

.question-translation {
  margin-top: -12px;
  margin-bottom: 24px;
  font-size: 0.95rem;
  color: var(--text-secondary);
  background: var(--bg-input);
  padding: 10px 14px;
  border-radius: var(--radius-md);
  border-left: 3px solid var(--accent-secondary);
  animation: slideUp 0.3s ease;
}

.question-translation.hidden {
  display: none;
}

.question-sentence .sentence-normal {
  font-weight: 300;
  color: var(--text-secondary);
}

.question-sentence .sentence-bold {
  font-weight: 700;
  color: var(--text-primary);
}

.question-sentence .sentence-blank {
  display: inline-block;
  min-width: 80px;
  border-bottom: 3px solid var(--accent-primary);
  text-align: center;
  font-weight: 700;
  color: var(--accent-primary);
  padding: 0 4px;
  margin: 0 4px;
  transition: all var(--transition-fast);
}

.question-sentence .sentence-blank.correct {
  border-color: var(--success);
  color: var(--success);
  background: var(--success-bg);
  border-radius: 4px;
}

.question-sentence .sentence-blank.wrong {
  border-color: var(--error);
  color: var(--error);
  background: var(--error-bg);
  border-radius: 4px;
}

/* Hint */
.hint-area {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 16px;
  min-height: 36px;
}

.hint-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  border-radius: var(--radius-full);
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--hint);
  transition: all var(--transition-fast);
}

.hint-btn:hover {
  background: var(--hint-bg);
  border-color: var(--hint);
}

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

.hint-text {
  font-size: 0.85rem;
  color: var(--hint);
  font-weight: 600;
  background: var(--hint-bg);
  padding: 6px 14px;
  border-radius: var(--radius-full);
  animation: fadeIn 0.3s ease;
}

/* Options Grid (Easy Mode) */
.options-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
  margin-top: 20px;
}

.option-btn {
  padding: 14px 16px;
  border: 2px solid var(--border);
  background: var(--bg-card);
  border-radius: var(--radius-md);
  cursor: pointer;
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  transition: all var(--transition-fast);
  font-family: 'Inter', sans-serif;
}

.option-btn:hover:not(:disabled) {
  border-color: var(--accent-primary);
  background: var(--accent-soft);
  transform: translateY(-1px);
}

.option-btn:active:not(:disabled) {
  transform: translateY(0);
}

.option-btn.correct {
  border-color: var(--success);
  background: var(--success-bg);
  color: var(--success);
}

.option-btn.wrong {
  border-color: var(--error);
  background: var(--error-bg);
  color: var(--error);
}

.option-btn:disabled {
  cursor: default;
  opacity: 0.7;
}

/* Input Area (Hard Mode) */
.input-area {
  display: flex;
  gap: 10px;
  margin-top: 20px;
}

.answer-input {
  flex: 1;
  padding: 14px 18px;
  border: 2px solid var(--border);
  background: var(--bg-input);
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  font-family: 'Inter', sans-serif;
  outline: none;
  transition: all var(--transition-fast);
}

.answer-input:focus {
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.answer-input.correct {
  border-color: var(--success);
  box-shadow: 0 0 0 3px var(--success-bg);
}

.answer-input.wrong {
  border-color: var(--error);
  box-shadow: 0 0 0 3px var(--error-bg);
}

.submit-btn {
  padding: 14px 24px;
  border: none;
  background: var(--accent-gradient);
  color: var(--text-on-accent);
  border-radius: var(--radius-md);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.submit-btn:hover {
  background: var(--accent-gradient-hover);
  transform: translateY(-1px);
}

.submit-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  transform: none;
}

/* Feedback */
.feedback-area {
  margin-top: 16px;
  animation: slideUp 0.3s ease;
}

.feedback-msg {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 16px;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 0.9rem;
}

.feedback-msg.correct {
  background: var(--success-bg);
  color: var(--success);
}

.feedback-msg.wrong {
  background: var(--error-bg);
  color: var(--error);
}

.next-btn {
  width: 100%;
  padding: 14px;
  border: none;
  background: var(--accent-gradient);
  color: var(--text-on-accent);
  border-radius: var(--radius-md);
  font-family: 'Outfit', sans-serif;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  margin-top: 12px;
}

.next-btn:hover {
  background: var(--accent-gradient-hover);
  transform: translateY(-1px);
}

/* ============================================================
   Results View
   ============================================================ */
.results-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  padding: 36px 28px;
  text-align: center;
  box-shadow: var(--shadow-lg);
  animation: scaleIn 0.4s ease;
}

.results-emoji {
  font-size: 56px;
  margin-bottom: 12px;
  display: block;
  animation: bounceIn 0.6s ease 0.2s both;
}

.results-title {
  font-family: 'Outfit', sans-serif;
  font-size: 1.6rem;
  font-weight: 800;
  margin-bottom: 8px;
}

.results-subtitle {
  color: var(--text-secondary);
  margin-bottom: 28px;
}

.results-stats {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 16px;
  margin-bottom: 28px;
}

.result-stat {
  padding: 16px;
  border-radius: var(--radius-md);
  background: var(--bg-input);
}

.result-stat .stat-num {
  font-family: 'Outfit', sans-serif;
  font-size: 2rem;
  font-weight: 800;
  display: block;
}

.result-stat .stat-num.correct-num { color: var(--success); }
.result-stat .stat-num.wrong-num { color: var(--error); }
.result-stat .stat-num.score-num {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.result-stat .stat-desc {
  font-size: 0.8rem;
  color: var(--text-tertiary);
  margin-top: 4px;
}

.results-mistakes {
  text-align: left;
  margin-top: 24px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.results-mistakes h3 {
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  font-size: 1rem;
  margin-bottom: 12px;
  color: var(--error);
  display: flex;
  align-items: center;
  gap: 6px;
}

.mistake-item {
  background: var(--bg-input);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  margin-bottom: 8px;
  border-left: 3px solid var(--error);
}

.mistake-item .mistake-sentence {
  font-size: 0.9rem;
  margin-bottom: 6px;
  color: var(--text-primary);
}

.mistake-item .mistake-answer {
  font-size: 0.8rem;
  color: var(--text-tertiary);
}

.mistake-item .mistake-answer .correct-answer {
  color: var(--success);
  font-weight: 700;
}

.mistake-item .mistake-answer .user-answer {
  color: var(--error);
  font-weight: 700;
  text-decoration: line-through;
}

.results-buttons {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 24px;
}

.results-buttons .btn-secondary {
  padding: 14px;
  border: 2px solid var(--border);
  background: var(--bg-card);
  border-radius: var(--radius-md);
  font-family: 'Outfit', sans-serif;
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.results-buttons .btn-secondary:hover {
  border-color: var(--accent-primary);
  background: var(--accent-soft);
}

.results-buttons .btn-primary {
  padding: 14px;
  border: none;
  background: var(--accent-gradient);
  border-radius: var(--radius-md);
  font-family: 'Outfit', sans-serif;
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  color: var(--text-on-accent);
  transition: all var(--transition-fast);
}

.results-buttons .btn-primary:hover {
  background: var(--accent-gradient-hover);
  transform: translateY(-1px);
}

/* ============================================================
   Mistakes Book View
   ============================================================ */
.view-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 24px;
}

.back-btn-icon {
  width: 40px;
  height: 40px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
  color: var(--text-secondary);
  transition: all var(--transition-fast);
  flex-shrink: 0;
}

.back-btn-icon:hover {
  background: var(--accent-soft);
  color: var(--accent-primary);
}

.view-title {
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  font-size: 1.3rem;
}

.view-header-actions {
  margin-left: auto;
  display: flex;
  gap: 8px;
}

.clear-btn {
  padding: 8px 14px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  border-radius: var(--radius-full);
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--error);
  transition: all var(--transition-fast);
}

.clear-btn:hover {
  background: var(--error-bg);
  border-color: var(--error);
}

.practice-mistakes-btn {
  padding: 8px 14px;
  border: none;
  background: var(--accent-gradient);
  border-radius: var(--radius-full);
  cursor: pointer;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-on-accent);
  transition: all var(--transition-fast);
}

.practice-mistakes-btn:hover {
  transform: translateY(-1px);
}

.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-tertiary);
}

.empty-state .empty-icon {
  font-size: 48px;
  margin-bottom: 12px;
  display: block;
  opacity: 0.5;
}

.empty-state .empty-text {
  font-size: 1rem;
  margin-bottom: 4px;
  font-weight: 500;
}

.empty-state .empty-desc {
  font-size: 0.85rem;
}

.mistakes-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.mistakes-list .mistake-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 16px;
  animation: slideUp 0.3s ease;
}

.mistake-card .mistake-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 8px;
}

.mistake-card .collocation-badge {
  background: var(--accent-soft);
  color: var(--accent-primary);
  padding: 4px 12px;
  border-radius: var(--radius-full);
  font-weight: 600;
  font-size: 0.85rem;
}

.mistake-card .mistake-count {
  font-size: 0.75rem;
  color: var(--text-tertiary);
}

.mistake-card .mistake-sentences {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.mistake-card .mistake-sentences p {
  margin-bottom: 4px;
  padding-left: 12px;
  border-left: 2px solid var(--border);
}

.mistake-card .delete-mistake {
  background: none;
  border: none;
  color: var(--text-tertiary);
  cursor: pointer;
  font-size: 16px;
  padding: 4px;
  transition: color var(--transition-fast);
}

.mistake-card .delete-mistake:hover {
  color: var(--error);
}

/* ============================================================
   Dictionary View
   ============================================================ */
.search-bar {
  position: relative;
  margin-bottom: 20px;
}

.search-bar input {
  width: 100%;
  padding: 14px 18px 14px 48px;
  border: 2px solid var(--border);
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  font-size: 1rem;
  color: var(--text-primary);
  outline: none;
  transition: all var(--transition-fast);
  font-family: 'Inter', sans-serif;
}

.search-bar input:focus {
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.search-bar input::placeholder {
  color: var(--text-tertiary);
}

.search-bar .search-icon {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 18px;
  color: var(--text-tertiary);
  pointer-events: none;
}

.dict-filter {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.filter-chip {
  padding: 6px 14px;
  border: 1px solid var(--border);
  background: var(--bg-card);
  border-radius: var(--radius-full);
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.filter-chip:hover {
  border-color: var(--accent-primary);
}

.filter-chip.active {
  background: var(--accent-gradient);
  color: white;
  border-color: transparent;
}

.dict-count {
  font-size: 0.85rem;
  color: var(--text-tertiary);
  margin-bottom: 16px;
}

.dict-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.dict-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  overflow: hidden;
  transition: all var(--transition-fast);
}

.dict-card:hover {
  border-color: var(--accent-primary);
  box-shadow: var(--shadow-sm);
}

.dict-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 16px;
  cursor: pointer;
}

.dict-card-header .dict-collocation {
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--accent-primary);
}

.dict-card-header .dict-meaning {
  font-size: 0.85rem;
  color: var(--text-tertiary);
}

.dict-card-header .expand-icon {
  font-size: 14px;
  color: var(--text-tertiary);
  transition: transform var(--transition-fast);
}

.dict-card.expanded .expand-icon {
  transform: rotate(180deg);
}

.dict-card-body {
  display: none;
  padding: 0 16px 14px;
  border-top: 1px solid var(--border);
}

.dict-card.expanded .dict-card-body {
  display: block;
  animation: slideUp 0.2s ease;
}

.dict-card-body .dict-sentence {
  font-size: 0.9rem;
  color: var(--text-secondary);
  padding: 8px 0;
  border-bottom: 1px solid var(--border);
  line-height: 1.6;
}

.dict-card-body .dict-sentence:last-child {
  border-bottom: none;
}

.dict-card-body .dict-sentence .sentence-bold {
  font-weight: 700;
  color: var(--text-primary);
}

.dict-card-body .dict-sentence .sentence-normal {
  font-weight: 300;
}

/* ============================================================
   Confirm Modal
   ============================================================ */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: var(--bg-overlay);
  z-index: 1000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 20px;
  backdrop-filter: blur(4px);
}

.modal-overlay.active {
  display: flex;
}

.modal-card {
  background: var(--bg-card);
  border-radius: var(--radius-xl);
  padding: 32px 28px;
  max-width: 360px;
  width: 100%;
  text-align: center;
  animation: scaleIn 0.25s ease;
  box-shadow: var(--shadow-xl);
}

.modal-card .modal-icon {
  font-size: 40px;
  margin-bottom: 12px;
  display: block;
}

.modal-card .modal-title {
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  font-size: 1.2rem;
  margin-bottom: 8px;
}

.modal-card .modal-desc {
  color: var(--text-secondary);
  font-size: 0.9rem;
  margin-bottom: 24px;
}

.modal-buttons {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px;
}

.modal-buttons .modal-cancel {
  padding: 12px;
  border: 2px solid var(--border);
  background: var(--bg-card);
  border-radius: var(--radius-md);
  font-weight: 600;
  cursor: pointer;
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.modal-buttons .modal-cancel:hover {
  border-color: var(--text-tertiary);
}

.modal-buttons .modal-confirm {
  padding: 12px;
  border: none;
  background: var(--error);
  color: white;
  border-radius: var(--radius-md);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.modal-buttons .modal-confirm:hover {
  opacity: 0.9;
}

/* ============================================================
   Auth UI (Login / Register)
   ============================================================ */
.auth-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  padding: 28px 24px;
  box-shadow: var(--shadow-md);
  margin-top: 24px;
  animation: scaleIn 0.35s ease;
}

.auth-tabs {
  display: flex;
  gap: 0;
  margin-bottom: 24px;
  background: var(--bg-input);
  border-radius: var(--radius-full);
  padding: 4px;
}

.auth-tab {
  flex: 1;
  padding: 10px 16px;
  border: none;
  background: transparent;
  border-radius: var(--radius-full);
  font-family: 'Outfit', sans-serif;
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text-tertiary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.auth-tab.active {
  background: var(--accent-gradient);
  color: var(--text-on-accent);
  box-shadow: 0 2px 8px rgba(108, 99, 255, 0.3);
}

.auth-tab:hover:not(.active) {
  color: var(--text-primary);
}

.auth-form {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.form-group {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.form-label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
}

.form-input {
  padding: 12px 16px;
  border: 2px solid var(--border);
  background: var(--bg-input);
  border-radius: var(--radius-md);
  font-size: 1rem;
  color: var(--text-primary);
  font-family: 'Inter', sans-serif;
  outline: none;
  transition: all var(--transition-fast);
}

.form-input:focus {
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px var(--accent-soft);
}

.form-input::placeholder {
  color: var(--text-tertiary);
}

.auth-error {
  padding: 10px 14px;
  background: var(--error-bg);
  color: var(--error);
  border-radius: var(--radius-md);
  font-size: 0.85rem;
  font-weight: 600;
  animation: slideUp 0.2s ease;
}

/* User Badge (Header) */
.user-badge {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 4px 8px 4px 4px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
}

.user-avatar {
  width: 30px;
  height: 30px;
  background: var(--accent-gradient);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 0.8rem;
  color: white;
}

.user-name {
  font-weight: 600;
  font-size: 0.85rem;
  color: var(--text-primary);
  max-width: 80px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.logout-btn {
  width: 28px;
  height: 28px;
  border: none;
  background: transparent;
  border-radius: 50%;
  cursor: pointer;
  font-size: 14px;
  color: var(--text-tertiary);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.logout-btn:hover {
  background: var(--error-bg);
  color: var(--error);
}

/* ============================================================
   Activity & Heatmap
   ============================================================ */
.activity-section {
  display: flex;
  flex-direction: column;
  gap: 16px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  margin-bottom: 24px;
}

.streak-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: linear-gradient(135deg, rgba(255, 107, 107, 0.1), rgba(255, 142, 83, 0.1));
  border: 1px solid rgba(255, 107, 107, 0.3);
  padding: 8px 16px;
  border-radius: var(--radius-full);
  align-self: flex-start;
}

.streak-icon {
  font-size: 1.2rem;
  animation: pulse 2s infinite ease-in-out;
}

.streak-text {
  font-weight: 600;
  color: var(--text-primary);
  font-size: 0.95rem;
}

.streak-text strong {
  color: #ff6b6b;
  font-size: 1.1rem;
}

.heatmap-container {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.heatmap-grid {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 4px;
}

.heatmap-cell {
  aspect-ratio: 1;
  border-radius: 4px;
  background: var(--bg-input);
  transition: transform var(--transition-fast), opacity var(--transition-fast);
}

.heatmap-cell:hover {
  transform: scale(1.15);
  box-shadow: 0 0 8px rgba(108, 99, 255, 0.4);
}

.heat-level-0 { background: var(--bg-input); }
.heat-level-1 { background: rgba(108, 99, 255, 0.2); }
.heat-level-2 { background: rgba(108, 99, 255, 0.5); }
.heat-level-3 { background: rgba(108, 99, 255, 0.8); }
.heat-level-4 { background: rgba(108, 99, 255, 1.0); }

.heatmap-labels {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.75rem;
  color: var(--text-tertiary);
}

.heatmap-legend {
  display: flex;
  align-items: center;
  gap: 4px;
}

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

/* ============================================================
   Leaderboard View
   ============================================================ */
.leaderboard-intro {
  text-align: center;
  margin-bottom: 24px;
}

.lb-trophy {
  font-size: 3rem;
  margin-bottom: 8px;
  filter: drop-shadow(0 4px 12px rgba(255, 215, 0, 0.4));
}

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

.lb-card {
  display: flex;
  align-items: center;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 16px;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-fast);
}

.lb-card:hover {
  transform: translateX(4px);
  border-color: var(--accent-primary);
}

.lb-card.rank-1-card {
  background: linear-gradient(to right, rgba(255, 215, 0, 0.1), var(--bg-card));
  border-left: 4px solid #FFD700;
}

.lb-card.rank-2-card {
  background: linear-gradient(to right, rgba(192, 192, 192, 0.1), var(--bg-card));
  border-left: 4px solid #C0C0C0;
}

.lb-card.rank-3-card {
  background: linear-gradient(to right, rgba(205, 127, 50, 0.1), var(--bg-card));
  border-left: 4px solid #CD7F32;
}

.lb-rank {
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--text-tertiary);
  width: 40px;
  text-align: center;
}

.lb-info {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.lb-name {
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 8px;
}

.lb-me-badge {
  background: var(--accent-gradient);
  color: var(--text-on-accent);
  font-size: 0.7rem;
  padding: 2px 6px;
  border-radius: 4px;
  font-weight: 600;
}

.lb-streak {
  font-size: 0.8rem;
  color: var(--text-secondary);
}

.lb-score {
  text-align: right;
}

.lb-score-val {
  font-weight: 800;
  font-size: 1.2rem;
  color: var(--accent-primary);
  font-family: 'Outfit', sans-serif;
}

.lb-score-label {
  font-size: 0.7rem;
  color: var(--text-tertiary);
}

.loading-state {
  text-align: center;
  padding: 40px;
  color: var(--text-tertiary);
}

/* ============================================================
   Offline Toast (PWA)
   ============================================================ */
.offline-toast {
  position: fixed;
  bottom: 24px;
  left: 50%;
  transform: translateX(-50%);
  background: var(--error);
  color: white;
  padding: 12px 20px;
  border-radius: var(--radius-full);
  font-size: 0.85rem;
  font-weight: 600;
  box-shadow: 0 4px 12px rgba(255, 107, 107, 0.4);
  z-index: 9999;
  animation: slideUp 0.3s ease;
  white-space: nowrap;
}

.offline-toast.hidden {
  display: none;
}

/* ============================================================
   Grammar Tips & Adaptive UI
   ============================================================ */
.grammar-tip {
  margin-top: 12px;
  padding: 10px 14px;
  background: rgba(108, 99, 255, 0.1);
  border-left: 4px solid var(--accent-primary);
  border-radius: 4px;
  font-size: 0.85rem;
  color: var(--text-primary);
  line-height: 1.5;
}

.dict-loading-sentinel {
  text-align: center;
  padding: 20px;
  color: var(--text-tertiary);
  font-size: 0.85rem;
}

div[data-difficulty="adaptive"] {
  border: 2px solid transparent;
}
div[data-difficulty="adaptive"].selected {
  border-color: #a855f7;
  background: linear-gradient(180deg, var(--bg-card), rgba(168, 85, 247, 0.05));
}
div[data-difficulty="adaptive"] .card-icon {
  filter: drop-shadow(0 2px 8px rgba(168, 85, 247, 0.4));
}

/* ============================================================
   Combos & Success States
   ============================================================ */
.combo-container {
  position: absolute;
  top: 15%;
  left: 50%;
  margin-left: -80px;
  width: 160px;
  text-align: center;
  font-size: 2.2rem;
  font-weight: 900;
  color: #ff5722;
  text-shadow: 0 4px 15px rgba(255, 87, 34, 0.4), 0 0 5px rgba(255,255,255,0.8);
  transform: scale(0);
  opacity: 0;
  pointer-events: none;
  z-index: 100;
}

.combo-pop {
  animation: popCombo 1s cubic-bezier(0.175, 0.885, 0.32, 1.275) forwards;
}

@keyframes popCombo {
  0% { transform: scale(0.5) rotate(-10deg); opacity: 0; }
  30% { transform: scale(1.2) rotate(5deg); opacity: 1; }
  70% { transform: scale(1) rotate(0deg); opacity: 1; }
  100% { transform: scale(0) rotate(10deg); opacity: 0; }
}

/* ============================================================
   Flashcards
   ============================================================ */
.flashcard-scene {
  width: 100%;
  max-width: 400px;
  height: 320px;
  perspective: 1000px;
  margin: 40px auto;
  cursor: pointer;
}

.flashcard {
  width: 100%;
  height: 100%;
  position: relative;
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  transform-style: preserve-3d;
}

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

.flashcard-face {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  border-radius: var(--radius-xl);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 32px;
  box-shadow: var(--shadow-lg);
  border: 1px solid var(--border);
  background: var(--bg-card);
}

.flashcard-front {
  background: var(--accent-gradient);
  color: var(--text-on-accent);
  border: none;
}

.flashcard-back {
  background: var(--bg-card);
  transform: rotateY(180deg);
}

.fc-blank-sentence {
  font-size: 1.5rem;
  font-weight: 700;
  text-align: center;
  line-height: 1.4;
  margin-bottom: 20px;
  font-family: 'Outfit', sans-serif;
}

.fc-hint {
  font-size: 1.1rem;
  opacity: 0.9;
  font-weight: 500;
}

.fc-instruction {
  position: absolute;
  bottom: 20px;
  font-size: 0.75rem;
  opacity: 0.7;
  letter-spacing: 1px;
  text-transform: uppercase;
}

.fc-answer {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--accent-primary);
  margin-bottom: 12px;
  font-family: 'Outfit', sans-serif;
}

.fc-meaning {
  font-size: 1.1rem;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.fc-sentence {
  font-size: 1.05rem;
  line-height: 1.5;
  color: var(--text-primary);
  text-align: center;
  margin-bottom: 8px;
}

.fc-translation {
  font-size: 0.9rem;
  color: var(--text-tertiary);
  text-align: center;
  margin-bottom: 20px;
}

.fc-tip {
  font-size: 0.8rem;
  background: var(--accent-soft);
  color: var(--accent-primary);
  padding: 10px 14px;
  border-radius: var(--radius-md);
  line-height: 1.4;
  max-width: 100%;
}

.flashcard-controls {
  display: flex;
  gap: 16px;
  justify-content: center;
  margin-top: 20px;
}

.fc-btn {
  padding: 12px 24px;
  border-radius: var(--radius-full);
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text-primary);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-family: 'Outfit', sans-serif;
}

.fc-btn:hover {
  background: var(--bg-input);
  border-color: var(--text-tertiary);
}

.fc-btn-primary {
  background: var(--accent-primary);
  color: var(--text-on-accent);
  border: none;
}

.fc-btn-primary:hover {
  background: var(--accent-secondary);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(108, 99, 255, 0.3);
}

.success-alert {
  background: rgba(34, 197, 94, 0.15);
  border-left: 4px solid var(--success);
  padding: 16px;
  border-radius: var(--radius-md);
  color: var(--success);
  font-weight: 600;
  text-align: center;
  margin-bottom: 20px;
}

/* ============================================================
   Scrollbar
   ============================================================ */
::-webkit-scrollbar {
  width: 6px;
}

::-webkit-scrollbar-track {
  background: transparent;
}

::-webkit-scrollbar-thumb {
  background: var(--border-strong);
  border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-tertiary);
}

/* ============================================================
   Responsive (Mobile Portrait)
   ============================================================ */
@media (max-width: 600px) {
  .app-container {
    padding: 12px;
  }

  .app-header {
    padding: 12px 0;
  }

  .app-logo .logo-text {
    font-size: 1.1rem;
  }

  .home-hero {
    padding: 24px 0 20px;
  }

  .home-hero .hero-emoji {
    font-size: 48px;
  }

  .home-hero h1 {
    font-size: 1.6rem;
  }

  .home-hero .subtitle {
    font-size: 0.9rem;
  }

  .difficulty-cards {
    grid-template-columns: 1fr 1fr;
    gap: 8px;
  }

  .difficulty-card {
    padding: 14px 10px;
  }

  .difficulty-card .card-icon {
    font-size: 26px;
  }

  .difficulty-card .card-title {
    font-size: 0.95rem;
  }

  .feature-grid {
    grid-template-columns: 1fr 1fr;
    gap: 8px;
  }

  .feature-card {
    padding: 14px 10px;
  }

  .stats-row {
    gap: 8px;
  }

  .stat-value {
    font-size: 1.2rem;
  }

  .question-card {
    padding: 20px 16px;
    border-radius: var(--radius-lg);
  }

  .question-sentence {
    font-size: 1.05rem;
  }

  .options-grid {
    grid-template-columns: 1fr 1fr;
    gap: 8px;
  }

  .option-btn {
    padding: 12px;
    font-size: 0.95rem;
  }

  .input-area {
    flex-direction: column;
  }

  .submit-btn {
    width: 100%;
  }

  .results-stats {
    grid-template-columns: 1fr 1fr 1fr;
    gap: 8px;
  }

  .result-stat {
    padding: 12px 8px;
  }

  .result-stat .stat-num {
    font-size: 1.5rem;
  }

  .results-buttons {
    grid-template-columns: 1fr;
  }

  .results-card {
    padding: 24px 16px;
  }

  .view-header {
    gap: 8px;
  }

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

  .view-header-actions {
    gap: 4px;
  }

  .clear-btn, .practice-mistakes-btn {
    padding: 6px 10px;
    font-size: 0.75rem;
  }

  .modal-card {
    padding: 24px 20px;
  }
}

@media (max-width: 380px) {
  .difficulty-cards {
    grid-template-columns: 1fr;
  }

  .feature-grid {
    grid-template-columns: 1fr;
  }

  .options-grid {
    grid-template-columns: 1fr;
  }

  .home-hero h1 {
    font-size: 1.4rem;
  }
}

/* ============================================================
   Remember Me Checkbox
   ============================================================ */
.remember-me-label {
  display: flex;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  font-size: 0.88rem;
  color: var(--text-secondary);
  margin-top: 12px;
  margin-bottom: 4px;
  user-select: none;
  -webkit-user-select: none;
}

.remember-me-label input[type="checkbox"] {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
}

.remember-me-check {
  position: relative;
  width: 20px;
  height: 20px;
  min-width: 20px;
  border: 2px solid var(--border-strong);
  border-radius: 6px;
  background: var(--bg-input);
  transition: all var(--transition-fast);
}

.remember-me-check::after {
  content: '';
  position: absolute;
  top: 2px;
  left: 6px;
  width: 5px;
  height: 10px;
  border: solid white;
  border-width: 0 2.5px 2.5px 0;
  transform: rotate(45deg) scale(0);
  transition: transform 0.2s ease;
}

.remember-me-label input[type="checkbox"]:checked ~ .remember-me-check {
  background: var(--accent-gradient);
  border-color: var(--accent-primary);
  box-shadow: 0 2px 8px rgba(108, 99, 255, 0.3);
}

.remember-me-label input[type="checkbox"]:checked ~ .remember-me-check::after {
  transform: rotate(45deg) scale(1);
}

.remember-me-label:hover .remember-me-check {
  border-color: var(--accent-primary);
}

/* ============================================================
   Utility
   ============================================================ */
.hidden {
  display: none !important;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

/* ============================================================
   Feature Card Highlight (Study Mode entry)
   ============================================================ */
.feature-card-highlight {
  background: var(--accent-gradient) !important;
  border-color: transparent !important;
  color: white !important;
  position: relative;
  overflow: hidden;
}

.feature-card-highlight::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(255,255,255,0.15) 0%, transparent 60%);
  pointer-events: none;
}

.feature-card-highlight .feature-title,
.feature-card-highlight .feature-desc {
  color: white !important;
}

.feature-card-highlight:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 28px rgba(108, 99, 255, 0.45);
}

/* ============================================================
   Study View — Layout
   ============================================================ */
#studyView {
  display: none;
  flex-direction: column;
  min-height: calc(100vh - 100px);
}

#studyView.active {
  display: flex;
}

/* Header */
.study-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 10px;
  gap: 8px;
}

.study-header-center {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}

.study-mode-badge {
  font-family: 'Outfit', sans-serif;
  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  color: var(--accent-primary);
  background: var(--accent-soft);
  padding: 3px 12px;
  border-radius: var(--radius-full);
}

.study-progress-text {
  font-family: 'Outfit', sans-serif;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-tertiary);
}

.study-progress-text span {
  color: var(--text-primary);
  font-weight: 700;
}

.study-stats-mini {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 2px;
  font-size: 0.78rem;
  font-weight: 700;
  font-family: 'Outfit', sans-serif;
}

.study-know-count {
  color: var(--success);
}

.study-again-count {
  color: var(--error);
}

/* Progress bar */
.study-progress-bar-wrap {
  width: 100%;
  height: 5px;
  background: var(--bg-input);
  border-radius: var(--radius-full);
  margin-bottom: 20px;
  overflow: hidden;
}

.study-progress-bar {
  height: 100%;
  background: var(--accent-gradient);
  border-radius: var(--radius-full);
  transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ============================================================
   Study Card
   ============================================================ */
.study-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  padding: 28px 24px;
  box-shadow: var(--shadow-lg);
  flex: 1;
  margin-bottom: 20px;
  animation: studyCardIn 0.35s ease;
  overflow-y: auto;
}

@keyframes studyCardIn {
  from { opacity: 0; transform: translateY(16px) scale(0.97); }
  to   { opacity: 1; transform: translateY(0) scale(1); }
}

.study-card-exit-right {
  animation: studyExitRight 0.28s ease forwards !important;
}

.study-card-exit-left {
  animation: studyExitLeft 0.28s ease forwards !important;
}

@keyframes studyExitRight {
  to { opacity: 0; transform: translateX(60px) scale(0.95); }
}

@keyframes studyExitLeft {
  to { opacity: 0; transform: translateX(-60px) scale(0.95); }
}

/* Card top badges */
.study-card-top {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.study-collocation-tag {
  background: var(--accent-soft);
  color: var(--accent-primary);
  font-family: 'Outfit', sans-serif;
  font-size: 0.8rem;
  font-weight: 700;
  padding: 4px 14px;
  border-radius: var(--radius-full);
  letter-spacing: 0.3px;
}

.study-pos-tag {
  background: var(--bg-input);
  color: var(--text-tertiary);
  font-size: 0.75rem;
  font-weight: 600;
  padding: 4px 10px;
  border-radius: var(--radius-full);
  font-family: 'Inter', sans-serif;
}

/* Big phrase */
.study-phrase {
  font-family: 'Outfit', sans-serif;
  font-size: 2rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 8px;
  line-height: 1.2;
  word-break: break-word;
}

/* Meaning */
.study-meaning {
  font-size: 1.1rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-bottom: 20px;
}

/* Divider */
.study-divider {
  width: 100%;
  height: 1px;
  background: var(--border);
  margin-bottom: 20px;
}

/* Sentences */
.study-sentences {
  display: flex;
  flex-direction: column;
  gap: 14px;
  margin-bottom: 16px;
}

.study-sentence-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 12px 14px;
  background: var(--bg-input);
  border-radius: var(--radius-md);
  border-left: 3px solid var(--border-strong);
  transition: border-color var(--transition-fast);
}

.study-sentence-primary {
  border-left-color: var(--accent-primary);
  background: var(--accent-soft);
}

.study-sentence-num {
  width: 22px;
  height: 22px;
  min-width: 22px;
  background: var(--bg-card);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--text-tertiary);
  margin-top: 1px;
  border: 1px solid var(--border);
}

.study-sentence-primary .study-sentence-num {
  background: var(--accent-primary);
  color: white;
  border-color: var(--accent-primary);
}

.study-sentence-body {
  flex: 1;
}

.study-sentence-text {
  font-size: 0.95rem;
  line-height: 1.6;
  color: var(--text-primary);
  font-weight: 400;
}

.study-answer-word {
  font-weight: 800;
  color: var(--accent-primary);
  font-style: normal;
}

.study-sentence-trans {
  font-size: 0.82rem;
  color: var(--text-tertiary);
  margin-top: 4px;
  font-style: italic;
}

/* Grammar tip */
.study-tip {
  font-size: 0.85rem;
  color: var(--hint);
  background: var(--hint-bg);
  padding: 10px 14px;
  border-radius: var(--radius-md);
  border-left: 3px solid var(--hint);
  font-weight: 500;
  margin-top: 4px;
  animation: fadeIn 0.3s ease;
}

/* ============================================================
   Study Action Buttons
   ============================================================ */
.study-actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 8px;
}

.study-btn-again,
.study-btn-know {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 18px 12px;
  border: 2px solid transparent;
  border-radius: var(--radius-lg);
  cursor: pointer;
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  transition: all var(--transition-fast);
  outline: none;
}

.study-btn-again {
  background: var(--error-bg);
  border-color: var(--error);
  color: var(--error);
}

.study-btn-again:hover {
  background: var(--error);
  color: white;
  transform: translateY(-2px);
  box-shadow: 0 4px 16px rgba(239, 68, 68, 0.35);
}

.study-btn-know {
  background: var(--success-bg);
  border-color: var(--success);
  color: var(--success);
}

.study-btn-know:hover {
  background: var(--success);
  color: white;
  transform: translateY(-2px);
  box-shadow: 0 4px 16px rgba(34, 197, 94, 0.35);
}

.study-btn-again:active,
.study-btn-know:active {
  transform: translateY(0);
}

.study-btn-icon {
  font-size: 1.5rem;
  font-weight: 900;
}

.study-btn-label {
  font-size: 0.95rem;
}

/* Keyboard hint row */
.study-key-hint {
  text-align: center;
  font-size: 0.72rem;
  color: var(--text-tertiary);
  margin-top: 4px;
}

/* ============================================================
   Study Mode Chooser
   ============================================================ */
.study-set-chooser {
  padding: 8px 0;
  animation: fadeIn 0.3s ease;
}

.study-chooser-title {
  font-family: 'Outfit', sans-serif;
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 16px;
  text-align: center;
}

.study-set-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 20px;
}

.study-set-btn {
  background: var(--bg-card);
  border: 2px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px 14px;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
}

.study-set-btn:hover {
  border-color: var(--accent-primary);
  background: var(--accent-soft);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.study-set-btn:active {
  transform: translateY(0);
}

.study-set-icon {
  font-size: 2rem;
  display: block;
}

.study-set-name {
  font-family: 'Outfit', sans-serif;
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--text-primary);
}

.study-set-desc {
  font-size: 0.78rem;
  color: var(--text-tertiary);
}

/* Custom count section */
.study-custom-count {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  text-align: center;
  animation: slideUp 0.25s ease;
}

.study-slider-label {
  display: block;
  font-size: 0.95rem;
  color: var(--text-secondary);
  margin-bottom: 12px;
  font-weight: 500;
}

.study-slider-label strong {
  font-family: 'Outfit', sans-serif;
  font-size: 1.4rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.study-slider {
  width: 100%;
  -webkit-appearance: none;
  appearance: none;
  height: 6px;
  border-radius: var(--radius-full);
  background: var(--bg-input);
  outline: none;
  cursor: pointer;
}

.study-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: var(--accent-gradient);
  cursor: pointer;
  box-shadow: 0 2px 8px rgba(108, 99, 255, 0.4);
  transition: transform var(--transition-fast);
}

.study-slider::-webkit-slider-thumb:hover {
  transform: scale(1.15);
}

/* ============================================================
   Study Complete Screen
   ============================================================ */
.study-complete {
  text-align: center;
  padding: 32px 16px;
  animation: scaleIn 0.4s ease;
}

.study-complete-emoji {
  font-size: 72px;
  display: block;
  margin-bottom: 16px;
  animation: bounceIn 0.6s ease;
}

.study-complete-title {
  font-family: 'Outfit', sans-serif;
  font-size: 1.6rem;
  font-weight: 800;
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 24px;
}

.study-complete-stats {
  display: flex;
  justify-content: center;
  gap: 32px;
  margin-bottom: 20px;
}

.study-cstat {
  text-align: center;
}

.study-cstat-val {
  font-family: 'Outfit', sans-serif;
  font-size: 2.5rem;
  font-weight: 900;
  line-height: 1;
  margin-bottom: 4px;
}

.study-cstat-know {
  color: var(--success);
}

.study-cstat-again {
  color: var(--error);
}

.study-cstat-label {
  font-size: 0.82rem;
  color: var(--text-tertiary);
  font-weight: 500;
}

.study-complete-hint {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: 28px;
  font-weight: 500;
}

.study-complete-btns {
  display: flex;
  flex-direction: column;
  gap: 12px;
}