:root {
  --bg-page: #f8fafc;
  --bg-card: #ffffff;
  --bg-subtle: #f1f5f9;
  --text-main: #0f172a;
  --text-secondary: #334155;
  --text-muted: #64748b;
  --border-light: #e2e8f0;
  --border-hover: #cbd5e1;

  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-soft: #eef2ff;
  --primary-border: #c7d2fe;

  --amber: #f59e0b;
  --amber-dark: #d97706;
  --amber-soft: #fffbeb;

  --emerald: #10b981;
  --emerald-dark: #059669;
  --emerald-soft: #ecfdf5;

  --rose: #f43f5e;
  --rose-dark: #e11d48;
  --rose-soft: #fff1f2;

  /* German Gender Accent Colors */
  --der-color: #2563eb;
  --der-bg: #eff6ff;
  --der-border: #bfdbfe;

  --die-color: #e11d48;
  --die-bg: #fff1f2;
  --die-border: #fecdd3;

  --das-color: #059669;
  --das-bg: #ecfdf5;
  --das-border: #a7f3d0;

  --radius-xl: 20px;
  --radius-lg: 16px;
  --radius-md: 12px;
  --radius-sm: 8px;

  --shadow-xs: 0 1px 2px rgba(15, 23, 42, 0.04);
  --shadow-sm: 0 4px 12px -2px rgba(15, 23, 42, 0.05);
  --shadow-md: 0 12px 24px -6px rgba(15, 23, 42, 0.08);
  --shadow-lg: 0 20px 40px -12px rgba(15, 23, 42, 0.14);
}

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

body {
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background-color: var(--bg-page);
  color: var(--text-main);
  line-height: 1.6;
  padding-bottom: 100px;
  -webkit-font-smoothing: antialiased;
}

/* =========================================
   Minimalist Sticky Top Header
   ========================================= */
.top-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border-light);
  padding: 12px 20px;
}

.header-inner {
  max-width: 1140px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
}

.flag-badge {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  background: linear-gradient(180deg, #18181b 33.3%, #ef4444 33.3%, #ef4444 66.6%, #facc15 66.6%);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.12);
  flex-shrink: 0;
}

.brand-title h1 {
  font-size: 1.12rem;
  font-weight: 800;
  color: var(--text-main);
  letter-spacing: -0.02em;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.brand-title p {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.status-pills {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.pill {
  background: var(--bg-subtle);
  border: 1px solid var(--border-light);
  color: var(--text-secondary);
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 0.82rem;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  gap: 5px;
  white-space: nowrap;
}

.pill.xp-pill {
  background: var(--amber-soft);
  border-color: #fde68a;
  color: var(--amber-dark);
}

.account-btn {
  cursor: pointer;
  background: var(--text-main);
  color: #ffffff;
  border: none;
  padding: 7px 14px;
  border-radius: 999px;
  font-size: 0.82rem;
  font-weight: 700;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: all 0.18s ease;
}

.account-btn:hover {
  background: var(--primary);
  transform: translateY(-1px);
}

.sync-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #94a3b8;
  display: inline-block;
}
.sync-dot.online {
  background: #10b981;
  box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.25);
}

.speed-btn {
  cursor: pointer;
  background: #ffffff;
  color: var(--text-secondary);
  border: 1px solid var(--border-light);
  padding: 6px 12px;
  border-radius: 999px;
  font-size: 0.8rem;
  font-weight: 700;
  transition: all 0.15s;
}

.speed-btn:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.voice-select {
  background: #ffffff;
  color: var(--text-secondary);
  border: 1px solid var(--border-light);
  padding: 6px 10px;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 600;
  max-width: 195px;
  outline: none;
  cursor: pointer;
}

/* =========================================
   Desktop Top Tabs & Mobile Bottom App Bar
   ========================================= */
.nav-container {
  max-width: 1140px;
  margin: 18px auto 0;
  padding: 0 20px;
}

.nav-tabs {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 6px;
  background: #eef2f6;
  padding: 5px;
  border-radius: 16px;
}

.nav-tab {
  border: none;
  background: transparent;
  padding: 10px 8px;
  border-radius: 12px;
  font-size: 0.88rem;
  font-weight: 700;
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.18s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  white-space: nowrap;
}

.nav-tab .tab-icon {
  font-size: 1.05rem;
}

.nav-tab:hover {
  color: var(--text-main);
}

.nav-tab.active {
  background: #ffffff;
  color: var(--primary);
  box-shadow: var(--shadow-xs);
}

/* =========================================
   Main Content & Clean Cards
   ========================================= */
.main-container {
  max-width: 1140px;
  margin: 20px auto;
  padding: 0 20px;
}

.tab-panel {
  display: none;
  animation: fadeUp 0.22s ease;
}

.tab-panel.active {
  display: block;
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

.card {
  background: var(--bg-card);
  border-radius: var(--radius-xl);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-light);
  margin-bottom: 20px;
}

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--bg-subtle);
}

.card-title {
  font-size: 1.12rem;
  font-weight: 800;
  color: var(--text-main);
  display: flex;
  align-items: center;
  gap: 8px;
}

/* Badges */
.badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 3px 10px;
  border-radius: 999px;
  font-size: 0.74rem;
  font-weight: 700;
}

.badge-der { background: var(--der-bg); color: var(--der-color); border: 1px solid var(--der-border); }
.badge-die { background: var(--die-bg); color: var(--die-color); border: 1px solid var(--die-border); }
.badge-das { background: var(--das-bg); color: var(--das-color); border: 1px solid var(--das-border); }
.badge-v2 { background: var(--primary-soft); color: var(--primary); border: 1px solid var(--primary-border); }
.badge-frame { background: var(--amber-soft); color: var(--amber-dark); border: 1px solid #fde68a; }

/* =========================================
   Buttons & Audio Speaker Pill
   ========================================= */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 9px 16px;
  border-radius: 12px;
  font-weight: 700;
  font-size: 0.88rem;
  cursor: pointer;
  border: 1px solid transparent;
  transition: all 0.15s ease;
  user-select: none;
}

.btn:active {
  transform: scale(0.98);
}

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

.btn-success {
  background: var(--emerald);
  color: #ffffff;
}
.btn-success:hover {
  background: var(--emerald-dark);
}

.btn-gold {
  background: var(--amber);
  color: #ffffff;
}
.btn-gold:hover {
  background: var(--amber-dark);
}

.btn-outline {
  background: #ffffff;
  color: var(--text-secondary);
  border-color: var(--border-light);
}
.btn-outline:hover {
  background: var(--bg-subtle);
  border-color: var(--border-hover);
}
.btn-outline.active {
  background: var(--primary-soft);
  color: var(--primary);
  border-color: var(--primary-border);
}

/* Audio Speaker Button */
.tts-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 5px;
  background: var(--primary-soft);
  color: var(--primary);
  border: 1px solid var(--primary-border);
  border-radius: 999px;
  padding: 4px 11px;
  font-size: 0.78rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.15s ease;
  flex-shrink: 0;
}

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

.tts-btn.speaking {
  background: var(--amber);
  color: #ffffff;
  border-color: var(--amber);
  animation: pulseWave 0.6s infinite alternate;
}

@keyframes pulseWave {
  from { transform: scale(1); }
  to { transform: scale(1.06); }
}

/* =========================================
   TAB 1: Skeleton Transformer & Sentence Builder
   ========================================= */
.formula-switcher {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}

.skeleton-stage {
  background: var(--bg-page);
  border: 1.5px dashed var(--border-hover);
  border-radius: var(--radius-lg);
  padding: 22px 16px;
  text-align: center;
}

.skeleton-blocks {
  display: flex;
  align-items: stretch;
  justify-content: center;
  gap: 10px;
  flex-wrap: wrap;
  margin: 16px 0;
}

.s-block {
  background: #ffffff;
  border-radius: 14px;
  padding: 12px 16px;
  min-width: 118px;
  border: 1.5px solid var(--border-light);
  box-shadow: var(--shadow-xs);
  cursor: pointer;
  transition: all 0.18s ease;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.s-block:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-sm);
  border-color: var(--primary-border);
}

.s-block .role-tag {
  font-size: 0.68rem;
  font-weight: 800;
  padding: 2px 8px;
  border-radius: 999px;
  margin-bottom: 6px;
  background: var(--bg-subtle);
  color: var(--text-muted);
}

.s-block .de-word {
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--text-main);
}

.s-block .zh-word {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-top: 2px;
}

.s-block.pos-v2 {
  background: #f5f3ff;
  border-color: #c4b5fd;
}
.s-block.pos-v2 .role-tag { background: #7c3aed; color: #fff; }

.s-block.pos-frame {
  background: #fffbeb;
  border-color: #fde68a;
}
.s-block.pos-frame .role-tag { background: #d97706; color: #fff; }

.s-block.pos-time {
  background: #f0f9ff;
  border-color: #bae6fd;
}
.s-block.pos-time .role-tag { background: #0284c7; color: #fff; }

.s-block.pos-place {
  background: #f0fdfa;
  border-color: #99f6e4;
}
.s-block.pos-place .role-tag { background: #0d9488; color: #fff; }

/* Sentence Puzzle */
.puzzle-dropzone {
  min-height: 64px;
  background: var(--bg-page);
  border: 1.5px dashed #94a3b8;
  border-radius: 14px;
  padding: 12px;
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  margin: 14px 0;
}

.puzzle-bank {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 14px 0;
  min-height: 46px;
}

.word-chip {
  background: #ffffff;
  border: 1.5px solid var(--border-hover);
  box-shadow: 0 2px 0 var(--border-light);
  padding: 8px 15px;
  border-radius: 12px;
  font-size: 0.98rem;
  font-weight: 700;
  color: var(--text-main);
  cursor: pointer;
  transition: all 0.14s ease;
  user-select: none;
}

.word-chip:hover {
  border-color: var(--primary);
  color: var(--primary);
  transform: translateY(-2px);
}

.word-chip.in-answer {
  background: var(--primary-soft);
  border-color: var(--primary);
  color: var(--primary);
}

/* =========================================
   TAB 2: Top 50 Verbs & Quiz
   ========================================= */
.verb-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(310px, 1fr));
  gap: 16px;
}

.verb-card {
  background: #ffffff;
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: 18px;
  transition: all 0.2s ease;
}

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

.verb-card-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--bg-subtle);
  margin-bottom: 10px;
}

.verb-inf {
  font-size: 1.28rem;
  font-weight: 800;
  color: var(--text-main);
}

.conj-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
}

.conj-table tr {
  cursor: pointer;
  border-bottom: 1px solid #f8fafc;
}

.conj-table tr:hover {
  background: var(--primary-soft);
}

.conj-table td {
  padding: 6px 8px;
}

.conj-pronoun {
  color: var(--text-muted);
  font-weight: 600;
  width: 38%;
}

.conj-form {
  font-weight: 800;
  color: var(--text-main);
}

.conj-form.irreg {
  color: var(--rose-dark);
}

.verb-example {
  margin-top: 12px;
  background: var(--bg-page);
  padding: 10px 12px;
  border-radius: 12px;
  font-size: 0.85rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.quiz-box {
  background: linear-gradient(135deg, #f8fafc 0%, #eef2ff 100%);
  border: 1.5px solid var(--primary-border);
  border-radius: var(--radius-lg);
  padding: 22px 18px;
  text-align: center;
}

.quiz-options {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 10px;
  max-width: 520px;
  margin: 16px auto 0;
}

.quiz-opt {
  background: #ffffff;
  border: 1.5px solid var(--border-hover);
  padding: 13px;
  border-radius: 12px;
  font-size: 1.05rem;
  font-weight: 800;
  color: var(--text-main);
  cursor: pointer;
  transition: all 0.15s ease;
}

.quiz-opt:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.quiz-opt.correct {
  background: var(--emerald-soft);
  border-color: var(--emerald);
  color: var(--emerald-dark);
}

.quiz-opt.wrong {
  background: var(--rose-soft);
  border-color: var(--rose);
  color: var(--rose-dark);
}

/* =========================================
   TAB 3: Vocabulary Flashcards
   ========================================= */
.vocab-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 14px;
}

.vocab-item {
  background: #ffffff;
  border-radius: var(--radius-lg);
  padding: 16px;
  border: 1px solid var(--border-light);
  cursor: pointer;
  transition: all 0.18s ease;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.vocab-item:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-sm);
  border-color: var(--border-hover);
}

.vocab-item.gender-der { border-left: 5px solid var(--der-color); background: #f8fbff; }
.vocab-item.gender-die { border-left: 5px solid var(--die-color); background: #fff9fa; }
.vocab-item.gender-das { border-left: 5px solid var(--das-color); background: #f6fef9; }

.vocab-de {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--text-main);
  margin-bottom: 4px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.vocab-zh {
  font-size: 0.88rem;
  color: var(--text-secondary);
  font-weight: 600;
}

.vocab-ex {
  margin-top: 10px;
  padding-top: 8px;
  border-top: 1px dashed var(--border-light);
  font-size: 0.82rem;
  color: var(--text-muted);
}

/* =========================================
   TAB 4: Daily 10 Sentences Translation
   ========================================= */
.day-selector {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 14px;
}

.sentence-task-card {
  background: #ffffff;
  border: 1.5px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: 18px;
  margin-bottom: 14px;
  transition: border-color 0.2s;
}

.sentence-task-card.solved {
  border-color: #6ee7b7;
  background: #f9fefb;
}

.task-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 10px;
  margin-bottom: 8px;
}

.task-zh {
  font-size: 1.06rem;
  font-weight: 800;
  color: var(--text-main);
}

.task-hint {
  font-size: 0.84rem;
  color: var(--text-secondary);
  background: var(--bg-page);
  padding: 8px 12px;
  border-radius: 10px;
  border-left: 3px solid var(--primary);
  margin-bottom: 10px;
}

.umlaut-bar {
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
  margin-bottom: 12px;
}

.umlaut-key {
  background: #ffffff;
  border: 1px solid var(--border-hover);
  border-radius: 8px;
  padding: 5px 11px;
  font-weight: 700;
  font-size: 0.88rem;
  cursor: pointer;
  transition: all 0.12s;
}

.umlaut-key:hover {
  background: var(--primary-soft);
  border-color: var(--primary);
  color: var(--primary);
}

.trans-input-row {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.trans-input {
  flex: 1;
  min-width: 210px;
  padding: 11px 14px;
  border: 1.5px solid var(--border-hover);
  border-radius: 12px;
  font-size: 0.98rem;
  font-family: inherit;
  color: var(--text-main);
  background: #ffffff;
  outline: none;
  transition: border-color 0.2s;
}

.trans-input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.feedback-panel {
  margin-top: 12px;
  padding: 14px;
  border-radius: 12px;
  background: var(--bg-page);
  border: 1px solid var(--border-light);
  display: none;
}

.feedback-panel.show { display: block; }
.feedback-panel.perfect { background: var(--emerald-soft); border-color: #6ee7b7; }
.feedback-panel.needs-fix { background: var(--amber-soft); border-color: #fde68a; }

/* =========================================
   TAB 5: Thoughts & Questions Notebook (随想与提问)
   ========================================= */
.note-composer {
  background: var(--bg-page);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: 18px;
  margin-bottom: 20px;
}

.note-input-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 10px;
  margin-top: 12px;
}

.note-textarea {
  width: 100%;
  min-height: 84px;
  padding: 12px 14px;
  border: 1.5px solid var(--border-hover);
  border-radius: 12px;
  font-family: inherit;
  font-size: 0.95rem;
  resize: vertical;
  outline: none;
}

.note-textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.note-card {
  background: #ffffff;
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: 16px 18px;
  margin-bottom: 12px;
  transition: all 0.18s;
}

.note-card.type-question { border-left: 4px solid var(--rose); }
.note-card.type-thought { border-left: 4px solid var(--primary); }
.note-card.type-phrase { border-left: 4px solid var(--emerald); }
.note-card.resolved { opacity: 0.72; border-left-color: #94a3b8; }

/* =========================================
   Floating Quick-Note Button & Account Modal
   ========================================= */
.fab-note-btn {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 95;
  background: var(--primary);
  color: #ffffff;
  border: none;
  border-radius: 999px;
  padding: 12px 18px;
  font-size: 0.9rem;
  font-weight: 800;
  box-shadow: 0 8px 24px rgba(79, 70, 229, 0.38);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: transform 0.2s, background 0.2s;
}

.fab-note-btn:hover {
  background: var(--primary-hover);
  transform: translateY(-2px);
}

.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.55);
  backdrop-filter: blur(6px);
  z-index: 200;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 16px;
}

.modal-backdrop.open {
  display: flex;
  animation: fadeUp 0.2s ease;
}

.modal-card {
  background: #ffffff;
  border-radius: var(--radius-xl);
  max-width: 460px;
  width: 100%;
  padding: 26px;
  box-shadow: var(--shadow-lg);
  border: 1px solid var(--border-light);
  max-height: 90vh;
  overflow-y: auto;
}

/* Reference Table */
.ref-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 8px;
  font-size: 0.88rem;
}

.ref-table th, .ref-table td {
  padding: 9px 12px;
  border-bottom: 1px solid var(--border-light);
  text-align: left;
}

.ref-table th {
  background: var(--bg-page);
  font-weight: 700;
  color: var(--text-secondary);
}

.ref-table tbody tr:hover {
  background: var(--primary-soft);
}

/* Audio Toast */
.audio-toast {
  position: fixed;
  bottom: 80px;
  left: 50%;
  transform: translateX(-50%) translateY(12px);
  background: rgba(15, 23, 42, 0.92);
  color: #fff;
  padding: 8px 16px;
  border-radius: 999px;
  font-size: 0.82rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 8px;
  box-shadow: var(--shadow-md);
  z-index: 300;
  opacity: 0;
  pointer-events: none;
  transition: all 0.2s ease;
  max-width: 90vw;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.audio-toast.visible {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

.eq-bars {
  display: inline-flex;
  align-items: flex-end;
  gap: 2px;
  height: 12px;
  flex-shrink: 0;
}

.eq-bars span {
  width: 2.5px;
  background: #38bdf8;
  border-radius: 2px;
  animation: eqBounce 0.45s infinite alternate;
}
.eq-bars span:nth-child(2) { animation-delay: 0.15s; background: #818cf8; }
.eq-bars span:nth-child(3) { animation-delay: 0.3s; background: #f472b6; }

@keyframes eqBounce {
  from { height: 3px; }
  to { height: 12px; }
}

/* =========================================
   Mobile Phone Adaptation (<= 768px)
   ========================================= */
@media (max-width: 768px) {
  body {
    padding-bottom: 130px;
  }

  .top-header {
    padding: 10px 14px;
  }

  .brand-title p {
    display: none;
  }

  .brand-title h1 {
    font-size: 1rem;
  }

  .voice-select {
    display: none;
  }

  /* Transform Nav into Native-like Fixed Bottom App Bar on Phones */
  .nav-container {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    margin: 0;
    padding: 0;
    z-index: 120;
    background: rgba(255, 255, 255, 0.96);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-top: 1px solid var(--border-light);
    box-shadow: 0 -4px 20px rgba(15, 23, 42, 0.06);
    padding-bottom: env(safe-area-inset-bottom, 6px);
  }

  .nav-tabs {
    background: transparent;
    padding: 4px 6px;
    border-radius: 0;
    gap: 2px;
  }

  .nav-tab {
    flex-direction: column;
    gap: 2px;
    padding: 6px 2px;
    font-size: 0.68rem;
    border-radius: 10px;
  }

  .nav-tab .tab-icon {
    font-size: 1.18rem;
  }

  .nav-tab.active {
    background: var(--primary-soft);
    box-shadow: none;
  }

  .main-container {
    margin: 14px auto;
    padding: 0 12px;
  }

  .card {
    padding: 16px;
    border-radius: 16px;
    margin-bottom: 14px;
  }

  .card-title {
    font-size: 1rem;
  }

  .s-block {
    min-width: 96px;
    padding: 10px 12px;
  }

  .s-block .de-word {
    font-size: 1.08rem;
  }

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

  .fab-note-btn {
    bottom: 76px;
    right: 14px;
    padding: 10px 15px;
    font-size: 0.82rem;
  }
}