:root {
  --bg: #F8FAFC;
  --surface: #FFFFFF;
  --surface-alt: #F1F5F9;
  --border: #CBD5E1;
  --text: #0F172A;
  --text-muted: #475569;
  --primary: #047857;
  --primary-dark: #065F46;
  --primary-soft: #D1FAE5;
  --accent: #0369A1;
  --accent-dark: #075985;
  --accent-soft: #E0F2FE;
  --danger: #B91C1C;
  --danger-dark: #991B1B;
  --danger-soft: #FEE2E2;
  --warn: #B45309;
  --warn-soft: #FEF3C7;
  --gold: #D97706;
  --sidebar-width: 248px;
  --bottom-nav-height: 68px;
  --radius-lg: 20px;
  --radius-md: 14px;
  --radius-sm: 10px;
}

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

body {
  font-family: system-ui, -apple-system, 'Segoe UI', Roboto, 'Noto Sans Thai', 'Noto Sans JP', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  min-height: 100vh;
}

.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;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 8px;
  background: var(--text);
  color: #FFFFFF;
  padding: 8px 14px;
  border-radius: 8px;
  z-index: 1000;
  font-weight: 700;
}
.skip-link:focus { left: 8px; }

:focus-visible {
  outline: 3px solid #0284C7;
  outline-offset: 2px;
}

/* App Layout */
.app-shell {
  display: flex;
  min-height: 100vh;
}

.sidebar {
  display: none;
}

.workspace {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0;
  padding-bottom: calc(var(--bottom-nav-height) + 16px);
}

.top-bar {
  position: sticky;
  top: 0;
  z-index: 30;
  background: var(--surface);
  border-bottom: 2px solid #E2E8F0;
  padding: 10px 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  flex-wrap: wrap;
}

.top-bar-left, .stats-group {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.course-switch-btn {
  background: var(--accent-soft);
  color: var(--accent-dark);
  border: 2px solid #BAE6FD;
  border-radius: 999px;
  padding: 6px 12px;
  font-family: inherit;
  font-weight: 800;
  font-size: 0.92rem;
  cursor: pointer;
}

.stat-pill {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  background: var(--surface-alt);
  border: 1.5px solid var(--border);
  border-radius: 999px;
  padding: 5px 11px;
  font-weight: 800;
  font-size: 0.9rem;
  color: var(--text);
}

.stat-hearts {
  background: #FFF1F2;
  border-color: #FECDD3;
  color: #9F1239;
  cursor: pointer;
  font-family: inherit;
}

.main-content {
  width: 100%;
  max-width: 760px;
  margin: 0 auto;
  padding: 16px;
  flex: 1;
}

/* Bottom Navigation (Mobile) */
.bottom-nav {
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  height: var(--bottom-nav-height);
  background: var(--surface);
  border-top: 2px solid #E2E8F0;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  z-index: 40;
  padding-bottom: env(safe-area-inset-bottom, 0);
}

.nav-item {
  appearance: none;
  background: transparent;
  border: none;
  font-family: inherit;
  color: var(--text-muted);
  font-weight: 700;
  font-size: 0.78rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  cursor: pointer;
  padding: 6px 4px;
}

.nav-item.active {
  color: var(--primary);
}

.nav-item-icon {
  font-size: 1.3rem;
  line-height: 1.1;
}

/* Desktop Breakpoint */
@media (min-width: 768px) {
  .mobile-only { display: none !important; }
  .bottom-nav { display: none; }

  .sidebar {
    display: flex;
    flex-direction: column;
    width: var(--sidebar-width);
    background: var(--surface);
    border-right: 2px solid #E2E8F0;
    padding: 20px 14px;
    position: sticky;
    top: 0;
    height: 100vh;
    gap: 20px;
    flex-shrink: 0;
  }

  .brand-box {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 4px 6px;
  }

  .brand-name {
    font-size: 1.35rem;
    font-weight: 900;
    color: var(--primary);
    line-height: 1.1;
  }

  .brand-sub {
    font-size: 0.82rem;
    color: var(--text-muted);
    font-weight: 600;
  }

  .sidebar-nav {
    display: flex;
    flex-direction: column;
    gap: 6px;
    flex: 1;
  }

  .sidebar-nav .nav-item {
    flex-direction: row;
    justify-content: flex-start;
    gap: 12px;
    font-size: 1rem;
    padding: 12px 14px;
    border-radius: var(--radius-md);
    text-align: left;
  }

  .sidebar-nav .nav-item:hover {
    background: var(--surface-alt);
  }

  .sidebar-nav .nav-item.active {
    background: var(--primary-soft);
    color: var(--primary-dark);
  }

  .sidebar-footer {
    display: flex;
    flex-direction: column;
    gap: 8px;
  }

  .workspace {
    padding-bottom: 24px;
  }
}

/* Buttons */
.btn {
  appearance: none;
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  font-family: inherit;
  font-weight: 800;
  font-size: 1rem;
  padding: 10px 18px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  transition: transform 0.08s ease, background-color 0.15s ease;
}
.btn:active:not(:disabled) { transform: translateY(2px); }
.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-sm { padding: 8px 12px; font-size: 0.88rem; }
.btn-xs { padding: 5px 10px; font-size: 0.8rem; border-radius: 999px; }
.btn-lg { padding: 13px 22px; font-size: 1.08rem; }
.btn-block { width: 100%; }

.btn-primary {
  background: var(--primary);
  color: #FFFFFF;
  border-bottom: 4px solid var(--primary-dark);
}
.btn-primary:hover:not(:disabled) { background: #059669; }

.btn-accent {
  background: var(--accent);
  color: #FFFFFF;
  border-bottom: 4px solid var(--accent-dark);
}

.btn-danger {
  background: var(--danger);
  color: #FFFFFF;
  border-bottom: 4px solid var(--danger-dark);
}

.btn-outline {
  background: var(--surface);
  color: var(--text);
  border-color: var(--border);
  border-bottom: 4px solid #94A3B8;
}

.icon-btn {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  border: 2px solid var(--border);
  background: var(--surface);
  color: var(--text);
  font-weight: 900;
  font-size: 1.05rem;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

/* Cards & Daily Goal */
.card {
  background: var(--surface);
  border: 2px solid #E2E8F0;
  border-radius: var(--radius-lg);
  padding: 16px;
  margin-bottom: 16px;
}

.daily-goal-card {
  background: var(--warn-soft);
  border: 2px solid #FCD34D;
  border-radius: var(--radius-lg);
  padding: 14px 16px;
  margin-bottom: 20px;
}

.daily-goal-top {
  display: flex;
  justify-content: space-between;
  font-weight: 800;
  font-size: 0.94rem;
  margin-bottom: 8px;
}

.progress-track {
  width: 100%;
  height: 12px;
  background: #E2E8F0;
  border-radius: 999px;
  overflow: hidden;
  flex: 1;
}

.progress-fill {
  height: 100%;
  background: #10B981;
  border-radius: 999px;
  transition: width 0.3s ease;
  width: 0%;
}

/* Skill Tree */
.unit-section {
  margin-bottom: 28px;
}

.unit-banner {
  border-radius: var(--radius-lg);
  padding: 16px 18px;
  color: #FFFFFF;
  margin-bottom: 18px;
  box-shadow: 0 4px 14px rgba(15, 23, 42, 0.1);
}

.unit-banner h2 {
  font-size: 1.2rem;
  font-weight: 900;
  margin-bottom: 4px;
}

.unit-banner p {
  font-size: 0.92rem;
  opacity: 0.95;
}

.nodes-path {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px;
  padding: 6px 0;
}

.node-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  max-width: 180px;
}

.lesson-node {
  width: 76px;
  height: 76px;
  border-radius: 50%;
  border: 4px solid #FFFFFF;
  font-family: inherit;
  font-size: 1.65rem;
  font-weight: 900;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 6px 0 rgba(15, 23, 42, 0.22);
  transition: transform 0.12s ease;
}

.lesson-node:active:not(:disabled) {
  transform: translateY(3px);
}

.lesson-node.unlocked {
  background: var(--primary);
  color: #FFFFFF;
}

.lesson-node.completed {
  background: #F59E0B;
  color: #451A03;
}

.lesson-node.checkpoint {
  background: #6D28D9;
  color: #FFFFFF;
}

.lesson-node.locked {
  background: #CBD5E1;
  color: #475569;
  cursor: not-allowed;
  box-shadow: 0 5px 0 #94A3B8;
}

.node-stars {
  margin-top: 6px;
  font-size: 0.88rem;
  letter-spacing: 1px;
}

.node-title {
  font-size: 0.86rem;
  font-weight: 700;
  color: var(--text);
  margin-top: 2px;
}

/* Lesson Overlay */
.lesson-overlay {
  position: fixed;
  inset: 0;
  background: var(--bg);
  z-index: 100;
  display: flex;
  justify-content: center;
}

.lesson-shell {
  width: 100%;
  max-width: 680px;
  height: 100%;
  background: var(--surface);
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
}

.lesson-header {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  border-bottom: 2px solid #E2E8F0;
}

.lesson-meta-pills {
  display: flex;
  align-items: center;
  gap: 6px;
}

.lesson-body {
  flex: 1;
  overflow-y: auto;
  padding: 20px 18px 110px 18px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.lesson-footer {
  padding: 14px 18px calc(14px + env(safe-area-inset-bottom, 0));
  border-top: 2px solid #E2E8F0;
  background: var(--surface);
}

/* Exercise UI */
.ex-badge {
  display: inline-block;
  align-self: flex-start;
  background: var(--accent-soft);
  color: var(--accent-dark);
  padding: 4px 12px;
  border-radius: 999px;
  font-size: 0.82rem;
  font-weight: 800;
}

.ex-prompt {
  font-size: 1.28rem;
  font-weight: 800;
  color: var(--text);
}

.ex-stimulus {
  background: var(--surface-alt);
  border: 2px solid #E2E8F0;
  border-radius: var(--radius-lg);
  padding: 18px;
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: 8px;
}

.ex-target-text {
  font-size: 1.8rem;
  font-weight: 900;
  color: var(--text);
}

.ex-romaji {
  font-size: 0.98rem;
  color: var(--accent-dark);
  font-weight: 700;
}

ruby rt {
  font-size: 0.55em;
  color: var(--accent-dark);
  font-weight: 700;
}

.romaji-hidden .ex-romaji {
  display: none;
}

.audio-controls {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: center;
}

.tts-warning {
  font-size: 0.85rem;
  color: var(--warn);
  background: var(--warn-soft);
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  font-weight: 700;
}

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

@media (min-width: 500px) {
  .options-grid.two-col {
    grid-template-columns: 1fr 1fr;
  }
}

.choice-btn {
  background: var(--surface);
  border: 2px solid var(--border);
  border-bottom: 4px solid #94A3B8;
  border-radius: var(--radius-md);
  padding: 14px 16px;
  font-family: inherit;
  font-size: 1.04rem;
  font-weight: 700;
  color: var(--text);
  text-align: left;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}
.choice-btn.selected {
  background: var(--accent-soft);
  border-color: var(--accent);
  border-bottom-color: var(--accent-dark);
}

.tile-slot {
  min-height: 62px;
  border: 2px dashed #94A3B8;
  border-radius: var(--radius-md);
  padding: 10px;
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  background: #FFFFFF;
}

.tile-bank {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  justify-content: center;
}

.tile-btn {
  background: var(--surface);
  border: 2px solid var(--border);
  border-bottom: 4px solid #94A3B8;
  border-radius: 12px;
  padding: 8px 14px;
  font-family: inherit;
  font-size: 1.02rem;
  font-weight: 700;
  color: var(--text);
  cursor: pointer;
}

.text-input {
  width: 100%;
  padding: 14px;
  font-family: inherit;
  font-size: 1.15rem;
  font-weight: 700;
  border: 2px solid var(--border);
  border-radius: var(--radius-md);
  color: var(--text);
  background: var(--surface);
}

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

.match-card {
  min-height: 58px;
  background: var(--surface);
  border: 2px solid var(--border);
  border-bottom: 4px solid #94A3B8;
  border-radius: var(--radius-md);
  padding: 10px;
  font-family: inherit;
  font-weight: 700;
  font-size: 0.98rem;
  color: var(--text);
  cursor: pointer;
}
.match-card.selected {
  background: var(--accent-soft);
  border-color: var(--accent);
}
.match-card.matched {
  background: var(--primary-soft);
  border-color: var(--primary);
  color: var(--primary-dark);
  cursor: default;
}

/* Bottom Feedback Bar */
.feedback-bar {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  padding: 16px 18px calc(16px + env(safe-area-inset-bottom, 0));
  transform: translateY(105%);
  transition: transform 0.22s ease;
  z-index: 20;
  display: flex;
  flex-direction: column;
  gap: 12px;
  box-shadow: 0 -8px 24px rgba(15, 23, 42, 0.14);
}
.feedback-bar.open { transform: translateY(0); }
.feedback-bar.correct {
  background: var(--primary-soft);
  border-top: 4px solid var(--primary);
  color: #064E3B;
}
.feedback-bar.wrong {
  background: var(--danger-soft);
  border-top: 4px solid var(--danger);
  color: #7F1D1D;
}

.feedback-inner {
  display: flex;
  align-items: center;
  gap: 12px;
}
.feedback-mascot { flex-shrink: 0; }
.feedback-title { font-size: 1.15rem; font-weight: 900; }
.feedback-explain { font-size: 0.95rem; font-weight: 600; }

/* Leaderboard & Tables */
.rank-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 14px;
  border-radius: var(--radius-md);
  border: 2px solid #E2E8F0;
  margin-bottom: 8px;
  background: var(--surface);
}
.rank-row.is-user {
  background: var(--primary-soft);
  border-color: var(--primary);
}

/* Modal */
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(15, 23, 42, 0.55);
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
}

.modal-card {
  background: var(--surface);
  border-radius: var(--radius-lg);
  padding: 24px 20px;
  width: 100%;
  max-width: 440px;
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 14px;
  box-shadow: 0 18px 40px rgba(15, 23, 42, 0.25);
}

.modal-title { font-size: 1.35rem; font-weight: 900; }
.modal-body { font-size: 0.98rem; color: var(--text-muted); width: 100%; }
.modal-actions { display: flex; flex-direction: column; gap: 8px; width: 100%; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
}