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

:root {
  --c-primary: #6366f1;
  --c-primary-light: #eef2ff;
  --c-primary-muted: rgba(99, 102, 241, 0.08);
  --c-accent: #d4537e;
  --c-success: #22c55e;
  --c-warning: #f59e0b;
  --c-danger: #ef4444;
  --c-bg: #f8fafc;
  --c-surface: #ffffff;
  --c-text: #0f172a;
  --c-text-secondary: #475569;
  --c-border: #e2e8f0;
  --radius-md: 12px;
  --radius-lg: 16px;
  --shadow-sm: 0 1px 4px rgba(99,102,241,0.06);
  --shadow-md: 0 4px 16px rgba(99,102,241,0.1);
  --shadow-lg: 0 8px 24px rgba(99,102,241,0.14);
}

@media (prefers-color-scheme: dark) {
  :root {
    --c-bg: #0b1120;
    --c-surface: #111827;
    --c-text: #f1f5f9;
    --c-text-secondary: #94a3b8;
    --c-border: #1e293b;
    --c-primary-light: rgba(99,102,241,0.12);
    --c-primary-muted: rgba(99,102,241,0.15);
    --shadow-sm: 0 1px 4px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.4);
    --shadow-lg: 0 8px 24px rgba(0,0,0,0.5);
  }
}

html {
  /* Fluid base: 14px @ 320px → 18px @ 1280px (smooth, no breakpoints) */
  font-size: clamp(14px, 0.85rem + 0.6vw, 18px);
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  background: var(--c-bg);
  color: var(--c-text);
  line-height: 1.6;
  min-height: 100vh;
  min-height: 100dvh;
}

/* ===== Register Trigger & Section ===== */
.scan-register-section {
  text-align: center;
  margin-bottom: 1rem;
}

.qr-code-wrapper {
  display: inline-block;
  padding: 0.5rem;
  background: #fff;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
}

.qr-code-img {
  width: 120px;
  height: 120px;
  object-fit: contain;
  display: block;
}

.scan-tip {
  font-size: clamp(0.6875rem, 1vw, 0.8125rem);
  color: var(--c-text-secondary);
  margin-top: 0.5rem;
}

/* ===== Divider ===== */
.divider {
  position: relative;
  text-align: center;
  margin: 1.5rem 0;
}

.divider::before {
  content: '';
  position: absolute;
  top: 50%;
  left: 0;
  right: 0;
  height: 1px;
  background: var(--c-border);
}

.divider span {
  position: relative;
  background: var(--c-surface);
  padding: 0 0.75rem;
  color: var(--c-text-secondary);
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
}

/* ===== Login Overlay ===== */
.overlay {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
  z-index: 1000;
}

.login-card {
  background: var(--c-surface);
  border-radius: var(--radius-lg);
  padding: 2.5rem 2rem;
  width: 90%;
  max-width: 400px;
  box-shadow: var(--shadow-md);
}

.login-header {
  text-align: center;
  margin-bottom: 2rem;
}

.login-header h1 {
  font-size: clamp(1.25rem, 2vw, 1.625rem);
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.login-header p {
  color: var(--c-text-secondary);
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
}

.form-group {
  margin-bottom: 1.25rem;
}

.form-group label {
  display: block;
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
  font-weight: 500;
  margin-bottom: 0.375rem;
  color: var(--c-text);
}

.form-group input {
  width: 100%;
  padding: 0.75rem 1rem;
  border: 1.5px solid var(--c-border);
  border-radius: var(--radius-md);
  font-size: clamp(0.875rem, 1.2vw, 1rem);
  background: var(--c-surface);
  color: var(--c-text);
  transition: border-color 0.2s;
}

.form-group input:focus {
  outline: none;
  border-color: var(--c-primary);
  box-shadow: 0 0 0 3px rgba(83, 74, 183, 0.15);
}

.error-msg {
  color: var(--c-danger);
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
  margin-bottom: 0.75rem;
  min-height: 1.25rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.625rem 1.25rem;
  border: 1.5px solid var(--c-border);
  border-radius: var(--radius-md);
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
  background: var(--c-surface);
  color: var(--c-text);
  text-decoration: none;
  gap: 0.375rem;
}

.btn:hover {
  border-color: var(--c-text-secondary);
}

.btn-primary {
  background: var(--c-primary);
  color: #fff;
  border-color: var(--c-primary);
}

.btn-primary:hover {
  opacity: 0.9;
}

.btn-block {
  width: 100%;
}

.btn-sm {
  padding: 0.375rem 0.75rem;
  font-size: clamp(0.6875rem, 1vw, 0.8125rem);
}

.btn-success {
  background: var(--c-success);
  color: #fff;
  border-color: var(--c-success);
}

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

.btn-warning {
  background: var(--c-warning);
  color: #fff;
  border-color: var(--c-warning);
}

/* ===== App Container ===== */
.app-container {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  min-height: 100dvh;
  min-width: 375px;
  max-width: 800px;
}

.top-nav {
  display: flex;
  flex-direction: column;
  padding: 0.75rem 1rem 0.5rem;
  gap: 0.5rem;
  background: var(--c-surface);
  border-bottom: 1px solid var(--c-border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}

.top-nav-main {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

.top-nav-slogan {
  text-align: center;
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
  color: var(--c-text-secondary);
  padding-top: 0.25rem;
  border-top: 1px solid var(--c-border);
}

.nav-category-selector {
  flex: 0 0 auto;
}

/* ===== Top Education Tabs (Horizontal Scroll) ===== */
.edu-tabs-wrapper {
  background: var(--c-surface);
  border-bottom: 1px solid var(--c-border);
  overflow-x: auto;
  white-space: nowrap;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;
}

.edu-tabs-wrapper::-webkit-scrollbar {
  display: none;
}

.edu-tabs {
  display: inline-flex;
  gap: 0;
  padding: 0 0.5rem;
}

.edu-tab-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 0.5rem 0.875rem;
  border: none;
  background: transparent;
  font-size: clamp(0.8125rem, 1.2vw, 1rem);
  color: var(--c-text-secondary);
  cursor: pointer;
  transition: all 0.2s;
  border-bottom: 2px solid transparent;
}

.edu-tab-btn.active {
  color: var(--c-primary);
  border-bottom-color: var(--c-primary);
  font-weight: 600;
}

.edu-tab-btn:hover {
  color: var(--c-primary);
  background: rgba(83, 74, 183, 0.05);
}

.edu-tab-content {
  padding: 1rem;
}

.edu-lesson-card {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  padding: 1rem;
  margin-bottom: 0.75rem;
  transition: all 0.2s;
}

.edu-lesson-card:hover {
  border-color: var(--c-primary);
  box-shadow: var(--shadow-sm);
}

.edu-lesson-title {
  font-size: clamp(0.9375rem, 1.5vw, 1.25rem);
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.edu-lesson-body {
  font-size: clamp(0.875rem, 1.3vw, 1.0625rem);
  line-height: 1.7;
  color: var(--c-text);
}

.edu-letter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(48px, 1fr));
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.edu-letter-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 0.5rem;
  border: 1px solid var(--c-border);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s;
}

.edu-letter-item:hover {
  border-color: var(--c-primary);
  background: rgba(83, 74, 183, 0.05);
}

.edu-letter-item .letter-char {
  font-size: clamp(1.5rem, 2.5vw, 2rem);
  font-weight: 600;
  color: var(--c-primary);
}

.edu-letter-item .letter-ipa {
  font-size: clamp(0.8125rem, 1.2vw, 1rem);
  color: var(--c-text-secondary);
  margin-top: 2px;
}

.edu-phoneme-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(64px, 1fr));
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.edu-phoneme-item {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 0.625rem;
  border: 1px solid var(--c-border);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s;
}

.edu-phoneme-item:hover {
  border-color: var(--c-accent);
  background: rgba(212, 83, 126, 0.05);
}

.edu-phoneme-item .phoneme-symbol {
  font-size: clamp(1.25rem, 2vw, 1.75rem);
  font-weight: 600;
  color: var(--c-accent);
}

.edu-phoneme-item .phoneme-desc {
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
  color: var(--c-text-secondary);
  margin-top: 4px;
  text-align: center;
}

.nav-brand {
  font-size: clamp(1.125rem, 1.8vw, 1.5rem);
}

.nav-user {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

/* ===== Category Selector in Top Nav ===== */
.nav-category-selector {
  flex: 0 0 auto;
}

.nav-category-selector select {
  padding: 0.375rem 0.75rem;
  border: 1.5px solid var(--c-border);
  border-radius: var(--radius-md);
  font-size: clamp(0.8125rem, 1.2vw, 1rem);
  background: var(--c-surface);
  color: var(--c-text);
  cursor: pointer;
  transition: border-color 0.2s;
  min-width: 100px;
}

.nav-category-selector select:focus {
  outline: none;
  border-color: var(--c-primary);
  box-shadow: 0 0 0 3px rgba(99,102,241,0.15);
}

.nav-category-selector select:hover {
  border-color: var(--c-text-secondary);
}

#nav-username {
  font-size: clamp(0.875rem, 1.3vw, 1.0625rem);
  color: var(--c-text-secondary);
}

/* ===== Stats Bar ===== */
.stats-bar {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.5rem;
  padding: 0.75rem 1rem;
  background: var(--c-surface);
  border-bottom: 1px solid var(--c-border);
  box-shadow: var(--shadow-sm);
}

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

.stat-value {
  font-size: clamp(1.25rem, 2.5vw, 2rem);
  font-weight: 700;
  color: var(--c-primary);
}

.stat-label {
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
  color: var(--c-text-secondary);
}

/* ===== Basics Navigation ===== */
.basics-nav {
  display: none;
  background: var(--c-surface);
  border-bottom: 1px solid var(--c-border);
  padding: 0 0.5rem;
  gap: 0;
  overflow-x: auto;
  scrollbar-width: none;
}
.basics-nav::-webkit-scrollbar { display: none; }
.basics-nav.visible {
  display: flex;
}

.basics-tab-btn {
  flex: 1;
  min-width: 60px;
  padding: 0.5rem 0.25rem;
  border: none;
  background: transparent;
  font-size: clamp(0.8125rem, 1.2vw, 1rem);
  font-weight: 500;
  color: var(--c-text-secondary);
  cursor: pointer;
  transition: all 0.2s;
  border-bottom: 3px solid transparent;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  white-space: nowrap;
}

.basics-tab-btn.active {
  color: var(--c-primary);
  border-bottom-color: var(--c-primary);
  font-weight: 600;
}

.basics-tab-btn:hover {
  color: var(--c-primary);
  background: var(--c-primary-muted);
}

.basics-content {
  display: none;
  padding: 1rem;
  background: var(--c-bg);
}
.basics-content.visible {
  display: block;
}

.basics-lesson-card {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  padding: 1rem;
  margin-bottom: 0.75rem;
  display: flex;
  align-items: center;
  gap: 1rem;
  transition: all 0.2s;
}

.basics-lesson-card:hover {
  border-color: var(--c-primary);
  box-shadow: var(--shadow-sm);
  transform: translateY(-2px);
}

.basics-char {
  font-size: clamp(1.25rem, 2.5vw, 2.5rem);
  font-weight: 700;
  color: var(--c-primary);
  min-width: 50px;
  text-align: center;
  cursor: pointer;
  transition: transform 0.15s;
}

.basics-char:hover {
  transform: scale(1.15);
}

.basics-info {
  flex: 1;
}

.basics-info .basic-title {
  font-size: clamp(0.9375rem, 1.4vw, 1.25rem);
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.basics-info .basic-desc {
  font-size: clamp(0.8125rem, 1.2vw, 1rem);
  color: var(--c-text-secondary);
  line-height: 1.5;
}

.play-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: clamp(32px, 3.5vw, 40px);
  height: clamp(32px, 3.5vw, 40px);
  border-radius: 50%;
  background: var(--c-primary);
  color: #fff;
  border: none;
  font-size: clamp(0.875rem, 1.2vw, 1.125rem);
  cursor: pointer;
  transition: all 0.2s;
  flex-shrink: 0;
}

.play-btn:hover {
  background: #4f46e5;
  transform: scale(1.1);
}

.play-btn.playing {
  animation: pulse-play 0.6s ease;
}

@keyframes pulse-play {
  0% { transform: scale(1); }
  50% { transform: scale(1.2); }
  100% { transform: scale(1); }
}

/* ===== Bottom Tabs (larger fonts) ===== */
.bottom-tabs {
  display: flex;
  background: var(--c-surface);
  border-top: 1px solid var(--c-border);
  position: fixed;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  max-width: 800px;
  width: 100%;
  z-index: 100;
  box-shadow: 0 -2px 10px rgba(0,0,0,0.05);
}

.tab-btn {
  flex: 1;
  padding: 0.625rem 0;
  border: none;
  background: transparent;
  font-size: clamp(0.8125rem, 1.2vw, 1rem);
  color: var(--c-text-secondary);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  transition: color 0.2s;
}

.tab-btn .tab-icon {
  font-size: clamp(1.25rem, 1.8vw, 1.5rem);
}

.tab-btn.active {
  color: var(--c-primary);
  font-weight: 600;
}

.tab-btn.active .tab-icon {
  transform: scale(1.1);
}

.panel {
  display: none;
  padding-bottom: 4rem;
  padding-top: 0.75rem;
  flex: 1;
}

.panel.active {
  display: block;
}

.panel-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 1rem;
}

.panel-header h2 {
  font-size: clamp(1rem, 1.6vw, 1.25rem);
  font-weight: 600;
  flex: 1;
}

.badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 1.5rem;
  height: 1.5rem;
  padding: 0 0.375rem;
  border-radius: 9999px;
  background: var(--c-primary);
  color: #fff;
  font-size: clamp(0.75rem, 1vw, 0.875rem);
  font-weight: 600;
  box-shadow: 0 2px 6px rgba(99,102,241,0.3);
}

/* ===== Word Card ===== */
.word-card {
  background: var(--c-surface);
  border: 1.5px solid var(--c-border);
  border-radius: 20px;
  margin: 0.75rem 1rem;
  padding: 1rem;
  box-shadow: var(--shadow-md);
  cursor: default;
  user-select: default;
  -webkit-tap-highlight-color: transparent;
  transition: box-shadow 0.3s ease, border-color 0.3s ease, transform 0.2s ease;
  border-left: 3px solid transparent;
}

.word-card:hover {
  box-shadow: var(--shadow-lg);
  border-color: rgba(99, 102, 241, 0.25);
  border-left: 3px solid var(--c-primary);
}

/* Confidence meter */
.confidence-meter {
  display: flex;
  align-items: center;
  gap: 4px;
  margin-top: 8px;
  font-size: 0.75rem;
  color: var(--c-text-secondary);
}

.confidence-bar {
  flex: 1;
  height: 4px;
  background: var(--c-border);
  border-radius: 2px;
  overflow: hidden;
}

.confidence-bar-fill {
  height: 100%;
  background: var(--c-primary);
  transition: width 0.3s ease;
}

.word-main {
  text-align: center;
  margin-bottom: 1.5rem;
}

.word-text {
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--c-primary);
  margin-bottom: 0.5rem;
  letter-spacing: -0.5px;
}

.word-phonetic {
  font-size: 1.0625rem;
  color: var(--c-text-secondary);
  margin-bottom: 0.5rem;
}

.word-pos {
  display: inline-block;
  margin-left: 0.5rem;
  padding: 0.125rem 0.625rem;
  border-radius: 9999px;
  background: var(--c-primary-light);
  color: var(--c-primary);
  font-size: 0.875rem;
}

.word-syllable {
  text-align: center;
  font-size: 1.5rem;
  font-weight: 600;
  color: var(--c-text);
  letter-spacing: 0.15em;
  margin-bottom: 1rem;
}

.syllable-sep {
  color: #ef4444;
  font-weight: 700;
  margin: 0 0.1em;
}

@media (prefers-color-scheme: dark) {
  .word-pos {
    background: #166534;
    color: #bbf7d0;
  }
}

.word-meaning {
  font-size: 1.25rem;
  font-weight: 500;
  color: var(--c-text);
  margin: 1rem 0;
  padding: 1rem;
  background: var(--c-primary-light);
  border-radius: var(--radius-md);
  line-height: 1.6;
  white-space: pre-wrap;
  word-break: break-word;
}

/* ===== Expanded Details Section ===== */
.word-details {
  display: none;
  flex-direction: column;
  gap: 0.75rem;
  margin: 1rem 0;
  padding: 1rem;
  background: linear-gradient(135deg, #f8fafc 0%, #f1f5f9 100%);
  border-radius: var(--radius-md);
  border: 1.5px solid var(--c-border);
}

@media (prefers-color-scheme: dark) {
  .word-details {
    background: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
  }
}

.expanded-field {
  display: flex;
  flex-direction: column;
  gap: 0.375rem;
}

.field-label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--c-primary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.field-content {
  font-size: clamp(0.9375rem, 1.4vw, 1.125rem);
  line-height: 1.6;
  color: var(--c-text);
}

.etymology-field .field-content {
  font-style: italic;
  color: var(--c-text-secondary);
}

.example-field .field-content {
  background: var(--c-primary-light);
  padding: 0.75rem;
  border-radius: 8px;
  border-left: 3px solid var(--c-primary);
}

@media (prefers-color-scheme: dark) {
  .example-field .field-content {
    background: rgba(99, 102, 241, 0.15);
  }
}

.collocation-field .field-content {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.collocation-tag {
  display: inline-block;
  padding: 0.25rem 0.625rem;
  background: var(--c-primary-light);
  color: var(--c-primary);
  border-radius: 9999px;
  font-size: clamp(0.875rem, 1.2vw, 1rem);
  font-weight: 500;
}

@media (prefers-color-scheme: dark) {
  .collocation-tag {
    background: rgba(99, 102, 241, 0.2);
    color: #a5b4fc;
  }
}

.example-sentence {
  font-size: 0.9375rem;
  color: var(--c-text-secondary);
  text-align: center;
  margin-bottom: 0.75rem;
  padding: 0.75rem;
  background: var(--c-primary-light);
  border-radius: var(--radius-md);
  line-height: 1.6;
}

.word-meaning.expanded-meaning {
  background: var(--c-primary-muted);
}

@media (prefers-color-scheme: dark) {
  .word-meaning.expanded-meaning {
    background: rgba(99,102,241,0.2);
  }
}

.example-sentence.expanded-example {
  background: var(--c-primary-muted);
  color: var(--c-text-secondary);
}

@media (prefers-color-scheme: dark) {
  .example-sentence.expanded-example {
    background: rgba(99,102,241,0.2);
  }
}

@media (prefers-color-scheme: dark) {
  .word-meaning {
    background: #1e293b;
  }
}

/* ===== Answer Options: one per row ===== */
.answer-options {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  margin-top: 1.25rem;
}

.option-btn {
  width: 100%;
  padding: 0.875rem 0.5rem;
  border: 1.5px solid var(--c-border);
  border-radius: 12px;
  background: var(--c-surface);
  color: var(--c-text);
  font-size: clamp(1rem, 1.5vw, 1.25rem);
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  text-align: left;
  white-space: normal;
  word-break: break-word;
  line-height: 1.6;
  display: flex;
  align-items: center;
}

.option-btn .option-text-content br {
  display: block;
  content: '';
  margin-bottom: 4px;
}

.option-btn:hover {
  border-color: var(--c-primary);
  background: var(--c-primary-light);
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

@media (prefers-color-scheme: dark) {
  .option-btn:hover {
    background: rgba(99,102,241,0.1);
  }
}

.option-btn.correct {
  border-color: var(--c-success);
  background: #f0fdf4;
  color: #16a34a;
  font-weight: 700;
  transform: scale(1.02);
}

.option-btn.incorrect {
  border-color: var(--c-danger);
  background: #fef2f2;
  color: #dc2626;
  opacity: 0.7;
}

.option-btn .option-word-prefix {
  display: none;
}

.option-btn.reveal-word .option-word-prefix {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 3px;
  padding: 8px 12px;
  min-width: 90px;
  max-width: 300px;
  background: linear-gradient(135deg, #eef2ff 0%, #e0e7ff 100%);
  border: 1.5px solid rgba(99, 102, 241, 0.25);
  border-radius: 12px;
  margin-right: 12px;
  vertical-align: top;
  opacity: 1;
  transition: opacity 0.25s ease;
  flex-shrink: 0;
  line-height: 1.3;
  box-shadow: 0 2px 8px rgba(99,102,241,0.1);
}

.option-btn.reveal-word .option-word-prefix .prefix-word {
  font-weight: 800;
  font-size: 1.7rem;
  color: #4338ca;
  white-space: nowrap;
  letter-spacing: 0.2px;
}

.option-btn.reveal-word .option-word-prefix .prefix-pron {
  color: #6366f1;
  font-weight: 500;
  font-size: 1.5rem;
  white-space: nowrap;
  font-family: "Lucida Sans Unicode", "Arial Unicode MS", sans-serif;
}

.option-btn .option-text-content {
  vertical-align: middle;
}

.quality-buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.5rem;
  margin-top: 1.25rem;
}

.quality-btn {
  padding: 0.75rem 0.5rem;
  border: 1.5px solid var(--c-border);
  border-radius: var(--radius-md);
  background: var(--c-surface);
  cursor: pointer;
  font-size: clamp(0.6875rem, 1vw, 0.8125rem);
  transition: all 0.15s;
}

.quality-btn:hover {
  transform: translateY(-2px) scale(1.02);
  box-shadow: var(--shadow-md);
}

.quality-btn.q-0 { border-color: var(--c-danger); color: var(--c-danger); background: rgba(239,68,68,0.1); }
.quality-btn.q-1 { border-color: #f97316; color: #f97316; background: rgba(249,115,22,0.1); }
.quality-btn.q-2 { border-color: #3b82f6; color: #3b82f6; background: rgba(59,130,246,0.1); }
.quality-btn.q-3 { border-color: var(--c-success); color: var(--c-success); background: rgba(34,197,94,0.1); }

.quality-btn.selected {
  transform: scale(1.05);
  box-shadow: var(--shadow-sm);
}

.quality-label {
  display: block;
  font-size: clamp(0.5625rem, 0.8vw, 0.6875rem);
  color: var(--c-text-secondary);
  margin-top: 2px;
}

/* ===== Categories ===== */
.categories-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 0.75rem;
  padding: 0.75rem 1rem;
}

.category-card {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s;
}

.category-card:hover {
  border-color: var(--c-primary);
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.category-icon {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}

.category-name {
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
  font-weight: 500;
}

.category-count {
  font-size: clamp(0.625rem, 0.9vw, 0.75rem);
  color: var(--c-text-secondary);
}

/* ===== Category Detail ===== */
.category-detail-header {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.75rem 1rem;
}

.back-btn {
  background: none;
  border: none;
  font-size: clamp(1rem, 1.4vw, 1.25rem);
  cursor: pointer;
  padding: 0.25rem;
  color: var(--c-text);
}

.detail-title {
  font-size: clamp(0.8125rem, 1.2vw, 1.0625rem);
  font-weight: 600;
}

/* ===== Category Word List ===== */
.word-list {
  padding: 0.75rem 1rem;
}

.word-list-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.75rem;
  margin-bottom: 0.5rem;
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  transition: all 0.2s;
}

.word-list-item:hover {
  border-color: var(--c-primary);
  box-shadow: var(--shadow-sm);
}

.word-list-word {
  font-weight: 600;
  color: var(--c-primary);
}

.word-list-meaning {
  font-size: clamp(0.875rem, 1.2vw, 1rem);
  color: var(--c-text-secondary);
  flex: 1;
  margin: 0 0.75rem;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.word-list-quality {
  font-size: clamp(0.75rem, 1.1vw, 0.9375rem);
  padding: 0.25rem 0.5rem;
  border-radius: 9999px;
  background: var(--c-primary-light);
  color: var(--c-primary);
}

/* ===== Confetti ===== */
.confetti-container {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 9999;
  overflow: hidden;
}

.confetti-piece {
  position: absolute;
  width: 8px;
  height: 8px;
  background: var(--c-primary);
  animation: confetti-fall 3s ease-in forwards;
}

@keyframes confetti-fall {
  0% { transform: translateY(-100vh) rotate(0deg); opacity: 1; }
  100% { transform: translateY(100vh) rotate(720deg); opacity: 0; }
}

/* ===== Mastery Modal ===== */
.mastery-modal {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(0,0,0,0.5);
  z-index: 2000;
}

.mastery-modal-content {
  background: var(--c-surface);
  border-radius: var(--radius-lg);
  padding: 2rem;
  max-width: 90%;
  width: 400px;
  text-align: center;
  box-shadow: var(--shadow-lg);
}

.mastery-modal-content h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 1rem;
  color: var(--c-primary);
}

.mastery-actions {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
  margin-top: 1.5rem;
}

/* ===== Learning Queue ===== */
.learning-queue {
  padding: 1rem;
}

.queue-item {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1rem;
  margin-bottom: 0.75rem;
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  transition: all 0.2s;
}

.queue-item:hover {
  border-color: var(--c-primary);
  transform: translateX(4px);
}

.queue-word {
  font-weight: 700;
  font-size: clamp(0.875rem, 1.4vw, 1.125rem);
  color: var(--c-primary);
}

.queue-meaning {
  font-size: 0.875rem;
  color: var(--c-text-secondary);
  flex: 1;
}

.queue-difficulty {
  display: flex;
  gap: 0.25rem;
}

.queue-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--c-border);
}

.queue-dot.filled {
  background: var(--c-primary);
}

/* ===== Word Preview Modal ===== */
.preview-modal {
  position: fixed;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(0,0,0,0.5);
  z-index: 2000;
}

.preview-modal-content {
  background: var(--c-surface);
  border-radius: var(--radius-lg);
  padding: 2rem;
  max-width: 90%;
  width: 500px;
  box-shadow: var(--shadow-lg);
}

.preview-word {
  font-size: 2rem;
  font-weight: 700;
  color: var(--c-primary);
  text-align: center;
  margin-bottom: 0.5rem;
}

.preview-phonetic {
  text-align: center;
  color: var(--c-text-secondary);
  margin-bottom: 1rem;
}

.preview-meaning {
  background: var(--c-primary-light);
  padding: 1rem;
  border-radius: var(--radius-md);
  margin-bottom: 1rem;
  line-height: 1.6;
}

.preview-actions {
  display: flex;
  gap: 0.75rem;
  justify-content: center;
}

/* ===== Loading ===== */
.loading-spinner {
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 3rem;
  color: var(--c-text-secondary);
}

.spinner {
  width: 2rem;
  height: 2rem;
  border: 3px solid var(--c-border);
  border-top-color: var(--c-primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin-right: 0.75rem;
}

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

/* ===== Empty State ===== */
.empty-state {
  text-align: center;
  padding: 3rem 1rem;
  color: var(--c-text-secondary);
}

.empty-icon {
  font-size: 3rem;
  margin-bottom: 1rem;
}

/* ===== Stats Panel ===== */
.stats-overview {
  padding: 0.75rem 1rem;
}

.chart-placeholder {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  height: 200px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--c-text-secondary);
  font-size: clamp(0.875rem, 1.2vw, 1.0625rem);
}

/* ===== Layout (non-font) Responsive ===== */
@media (min-width: 768px) {
  .app-container {
    min-width: 375px;
    max-width: 800px;
    margin: 0 auto;
    border-left: 1px solid var(--c-border);
    border-right: 1px solid var(--c-border);
  }
  .answer-options {
    grid-template-columns: repeat(4, 1fr);
  }
  .categories-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}

@media (min-width: 1280px) {
  .categories-grid {
    grid-template-columns: repeat(4, 1fr);
  }
}

@media (max-width: 360px) {
  .stats-bar {
    grid-template-columns: repeat(2, 1fr);
  }
}

/* Demo 模式提示 */
.demo-hint {
  color: #888;
  font-size: 12px;
  margin-top: 8px;
  text-align: center;
}

.demo-hint:hover {
  color: #666;
}

/* ===== Chart Rows ===== */
.chart-row {
  margin: 0.75rem 1rem;
}

.chart-container {
  background: var(--c-surface);
  border: 1px solid var(--c-border);
  border-radius: var(--radius-md);
  padding: 1rem;
  min-height: 220px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.2s;
}

.chart-container:hover {
  box-shadow: var(--shadow-md);
}

.chart-container canvas {
  width: 100% !important;
  height: 220px !important;
}

/* ===== P2: Frontend UX Enhancements ===== */

/* Smooth page transitions */
.panel {
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Toast notification */
.toast-notification {
  position: fixed;
  top: 1rem;
  right: 1rem;
  background: #1e293b;
  color: #fff;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  font-size: clamp(0.875rem, 1.2vw, 1.0625rem);
  z-index: 9999;
  animation: slideInRight 0.3s ease;
  box-shadow: var(--shadow-md);
}

.toast-notification.success { background: #22c55e; }
.toast-notification.error { background: #ef4444; }
.toast-notification.info { background: #3b82f6; }

@keyframes slideInRight {
  from { transform: translateX(100%); opacity: 0; }
  to { transform: translateX(0); opacity: 1; }
}

/* Keyboard shortcut hint */
.kbd-hint {
  display: inline-block;
  padding: 0.125rem 0.375rem;
  border: 1px solid var(--c-border);
  border-radius: 4px;
  background: #f1f5f9;
  font-size: clamp(0.75rem, 1vw, 0.875rem);
  color: var(--c-text-secondary);
  font-family: monospace;
}

/* Progress bar */
.progress-bar-container {
  width: 100%;
  height: 6px;
  background: var(--c-border);
  border-radius: 3px;
  overflow: hidden;
  margin: 0.5rem 0;
}

.progress-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, #6366f1, #818cf8);
  transition: width 0.5s ease;
}

/* Floating action button */
.fab-btn {
  position: fixed;
  bottom: 4rem;
  right: 1rem;
  width: 3rem;
  height: 3rem;
  border-radius: 50%;
  background: var(--c-primary);
  color: #fff;
  border: none;
  font-size: 1.25rem;
  cursor: pointer;
  box-shadow: var(--shadow-md);
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: transform 0.2s;
}

.fab-btn:hover {
  transform: scale(1.1);
}

/* Confetti animation for streak milestone */
@keyframes confetti-fall {
  0% { transform: translateY(-100vh) rotate(0deg); opacity: 1; }
  100% { transform: translateY(100vh) rotate(720deg); opacity: 0; }
}

.confetti-piece {
  position: fixed;
  width: 8px;
  height: 8px;
  background: var(--c-primary);
  z-index: 10000;
  animation: confetti-fall 3s ease-in forwards;
}

/* ===== Speaking Panel ===== */
.difficulty-select {
  padding: 0.375rem 0.75rem;
  border: 1.5px solid var(--c-border);
  border-radius: var(--radius-md);
  font-size: clamp(0.8125rem, 1.2vw, 1rem);
  background: var(--c-surface);
  color: var(--c-text);
  cursor: pointer;
  transition: border-color 0.2s;
}
.difficulty-select:focus {
  outline: none;
  border-color: var(--c-primary);
  box-shadow: 0 0 0 3px rgba(99,102,241,0.15);
}

.challenge-area {
  padding: 0.75rem 1rem;
}

.prompt-card {
  background: var(--c-surface);
  border: 1.5px solid var(--c-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem 1rem;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: box-shadow 0.3s ease;
}
.prompt-card:hover {
  box-shadow: var(--shadow-md);
}

.prompt-meta {
  display: flex;
  gap: 0.75rem;
  align-items: center;
  justify-content: center;
  margin-bottom: 0.5rem;
}

.question-counter {
  font-size: 0.8125rem;
  color: var(--c-text-secondary);
  font-weight: 600;
}

.prompt-actions {
  display: flex;
  gap: 0.5rem;
  justify-content: center;
  margin-top: 0.75rem;
}

.prompt-scene {
  font-size: 0.8125rem;
  color: var(--c-primary);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.5rem;
}

.prompt-text {
  font-size: clamp(1.5rem, 3vw, 2.5rem);
  font-weight: 700;
  color: var(--c-text);
  margin: 1rem 0;
}

/* Score Card */
.score-card {
  background: var(--c-surface);
  border: 1.5px solid var(--c-border);
  border-radius: var(--radius-lg);
  padding: 1.5rem 1rem;
  margin-top: 1rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1rem;
}

.score-circle {
  width: 100px;
  height: 100px;
  border-radius: 50%;
  background: conic-gradient(var(--c-primary) 0%, var(--c-border) 0%);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
}
.score-circle::before {
  content: '';
  position: absolute;
  inset: 4px;
  border-radius: 50%;
  background: var(--c-surface);
}
.score-number {
  position: relative;
  z-index: 1;
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--c-primary);
}
.score-label {
  position: relative;
  z-index: 1;
  font-size: 0.6875rem;
  color: var(--c-text-secondary);
}

.score-details {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.score-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.875rem;
}
.score-row-label {
  min-width: 50px;
  color: var(--c-text-secondary);
}
.mini-bar {
  flex: 1;
  height: 6px;
  background: var(--c-border);
  border-radius: 3px;
  overflow: hidden;
}
.mini-bar-fill {
  height: 100%;
  background: var(--c-primary);
  transition: width 0.5s ease;
}
.score-row > span:last-child {
  min-width: 30px;
  text-align: right;
  font-weight: 600;
  font-size: 0.8125rem;
}

/* Transcript & Feedback Cards */
.transcript-card,
.feedback-card {
  margin-top: 1rem;
  padding: 1rem;
  background: linear-gradient(135deg, #f8fafc 0%, #f1f5f9 100%);
  border-radius: var(--radius-md);
  border: 1.5px solid var(--c-border);
}
.field-label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--c-primary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  display: block;
  margin-bottom: 0.375rem;
}
.field-content {
  font-size: clamp(0.9375rem, 1.4vw, 1.125rem);
  line-height: 1.6;
  color: var(--c-text);
}

/* Recording Controls */
.recording-controls {
  padding: 1rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.75rem;
}

.waveform-canvas {
  width: 100%;
  height: 80px;
  background: var(--c-surface);
  border-radius: var(--radius-md);
  border: 1px solid var(--c-border);
}

.recorder-btns {
  display: flex;
  gap: 0.75rem;
  align-items: center;
}

.mic-record-btn {
  width: 120px;
  height: 120px;
  border-radius: 50%;
  border: none;
  background: linear-gradient(135deg, var(--c-primary), #8b5cf6);
  color: #fff;
  font-size: clamp(0.875rem, 1.3vw, 1.125rem);
  font-weight: 600;
  cursor: pointer;
  box-shadow: var(--shadow-lg);
  transition: all 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 4px;
}
.mic-record-btn:hover {
  transform: scale(1.05);
  box-shadow: 0 12px 32px rgba(99,102,241,0.3);
}
.mic-record-btn.recording {
  animation: mic-pulse 1s ease infinite;
  background: linear-gradient(135deg, #ef4444, #f97316);
}
.mic-record-btn .mic-icon {
  font-size: 2rem;
}
.mic-record-btn .mic-label {
  font-size: 0.6875rem;
  opacity: 0.9;
}

@keyframes mic-pulse {
  0%, 100% { transform: scale(1); box-shadow: 0 4px 16px rgba(239,68,68,0.3); }
  50% { transform: scale(1.1); box-shadow: 0 8px 32px rgba(239,68,68,0.5); }
}

.streak-display {
  font-size: 0.875rem;
  color: var(--c-warning);
  font-weight: 600;
}
.streak-display .count {
  font-size: 1.25rem;
  color: var(--c-danger);
}

/* Show answer button */
#show-answer-btn {
  margin-top: 0.5rem;
}

@media (prefers-color-scheme: dark) {
  .transcript-card,
  .feedback-card {
    background: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
  }
}