:root {
  --bg: #ffffff;
  --bg-soft: #ffffff;
  --surface: #ffffff;
  --surface-2: #f8fafc;
  --text: #111827;
  --muted: #64748b;
  --border: #e2e8f0;
  --accent: #4f46e5;
  --accent-2: #7c3aed;
  --accent-light: #eef2ff;
  --accent-glow: rgba(99, 102, 241, 0.45);
  --warm: #f59e0b;
  --success: #059669;
  --locked: #9ca3af;
  --shadow: 0 4px 24px rgba(15, 14, 26, 0.08);
  --shadow-hover: 0 16px 48px rgba(79, 70, 229, 0.22);
  --radius: 18px;
  --radius-sm: 12px;
}

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

html {
  scroll-behavior: smooth;
}

body.hub {
  font-family: "PingFang TC", "Heiti TC", "Noto Sans TC", system-ui, sans-serif;
  background: var(--bg-soft);
  color: var(--text);
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

.hub-bg {
  display: none;
}

.strings-deco {
  position: fixed;
  top: 0;
  right: 0;
  width: min(200px, 30vw);
  height: 100%;
  opacity: 0.04;
  pointer-events: none;
  z-index: 0;
  color: var(--accent);
}

.hub-wrap {
  position: relative;
  z-index: 1;
  max-width: 520px;
  margin: 0 auto;
  padding: 1.5rem 1.15rem 3.5rem;
}

/* ── Hero ── */

.hub-hero {
  text-align: center;
  padding: 1.25rem 0 1.75rem;
  animation: fadeUp 0.55s ease-out;
}

@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(14px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.hub-brand {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 4rem;
  height: 4rem;
  margin-bottom: 1rem;
  border-radius: 20px;
  background: linear-gradient(145deg, #6366f1, #4f46e5 45%, #7c3aed);
  box-shadow:
    0 8px 32px var(--accent-glow),
    inset 0 1px 0 rgba(255, 255, 255, 0.25);
}

.hub-mark {
  font-size: 1.75rem;
  font-weight: 800;
  color: #fff;
  letter-spacing: -0.04em;
  line-height: 1;
}

.hub-kicker {
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.45rem;
}

.hub-hero h1 {
  font-size: clamp(1.65rem, 6vw, 2rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  margin-bottom: 1rem;
  color: var(--text);
}

.hub-pills {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  justify-content: center;
}

.hub-pills li {
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.3rem 0.7rem;
  border-radius: 999px;
  background: var(--accent-light);
  color: var(--accent);
  border: 1px solid #e0e7ff;
}

/* ── Continue banner ── */

.continue-banner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  background: var(--surface-2);
  color: var(--text);
  padding: 1rem 1.15rem;
  border-radius: var(--radius);
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
  animation: fadeUp 0.45s ease-out 0.05s both;
}

.continue-banner[hidden] {
  display: none !important;
}

.continue-label {
  display: block;
  font-size: 0.72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
  margin-bottom: 0.2rem;
}

.continue-banner-text p {
  font-size: 0.95rem;
  color: var(--muted);
  line-height: 1.4;
}

.continue-banner-text strong {
  color: var(--text);
  font-weight: 700;
}

.btn-continue {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #fff;
  border: none;
  padding: 0.65rem 1.35rem;
  border-radius: 999px;
  font-weight: 700;
  font-size: 0.88rem;
  cursor: pointer;
  white-space: nowrap;
  transition: transform 0.15s, box-shadow 0.15s;
  box-shadow: 0 4px 16px var(--accent-glow);
}

.btn-continue:hover {
  transform: translateY(-1px);
  box-shadow: 0 8px 24px var(--accent-glow);
}

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

/* ── Sections ── */

.hub-main {
  display: flex;
  flex-direction: column;
  gap: 1.75rem;
}

.hub-section {
  animation: fadeUp 0.5s ease-out both;
}

.hub-section:nth-child(1) {
  animation-delay: 0.1s;
}

.hub-section:nth-child(2) {
  animation-delay: 0.16s;
}

.hub-section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.75rem;
  margin-bottom: 0.85rem;
  padding: 0 0.15rem;
}

.hub-section-title {
  font-size: 1.05rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--text);
}

.hub-section-meta {
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--muted);
}

.hub-section-link {
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--accent);
  text-decoration: none;
}

.hub-section-link:hover {
  text-decoration: underline;
}

/* ── Lesson grid & cards ── */

.lesson-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 1rem;
}

.lesson-card {
  position: relative;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.35rem 1.35rem 1.2rem;
  box-shadow: var(--shadow);
  transition:
    transform 0.22s cubic-bezier(0.34, 1.4, 0.64, 1),
    box-shadow 0.22s,
    border-color 0.22s;
  animation: cardIn 0.45s ease-out both;
  cursor: default;
  overflow: hidden;
}

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

.lesson-card.available {
  cursor: pointer;
}

.lesson-card.available:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-hover);
  border-color: #c7d2fe;
}

.lesson-card.available:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
}

.lesson-card.available::after {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2), var(--warm));
  border-radius: var(--radius) var(--radius) 0 0;
  opacity: 0.85;
}

.card-top {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 0.75rem;
}

.lesson-num {
  font-size: 2.35rem;
  font-weight: 800;
  line-height: 1;
  background: linear-gradient(135deg, var(--accent), #818cf8);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.card-badge {
  font-size: 0.68rem;
  font-weight: 700;
  padding: 0.28rem 0.65rem;
  border-radius: 999px;
}

.badge-open {
  background: #d1fae5;
  color: var(--success);
}

.lesson-card h3 {
  font-size: 1.2rem;
  font-weight: 800;
  margin-bottom: 0.45rem;
  letter-spacing: -0.02em;
}

.lesson-card .desc {
  font-size: 0.88rem;
  color: var(--muted);
  line-height: 1.55;
  margin-bottom: 0.9rem;
}

.topic-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  margin-bottom: 1rem;
}

.topic-tags span {
  font-size: 0.72rem;
  padding: 0.22rem 0.55rem;
  background: var(--accent-light);
  color: var(--accent);
  border-radius: 8px;
  font-weight: 600;
}

.card-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: 0.9rem;
  border-top: 1px solid var(--border);
}

.card-meta {
  font-size: 0.8rem;
  color: var(--muted);
}

.card-action {
  font-weight: 700;
  color: var(--accent);
  font-size: 0.88rem;
  display: inline-flex;
  align-items: center;
  gap: 0.2rem;
}

/* ── Song cards ── */

.hub-songs-grid {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.hub-song-card {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  padding: 1rem 1.1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow);
  transition: transform 0.2s, box-shadow 0.2s, border-color 0.2s;
  animation: cardIn 0.45s ease-out both;
}

.hub-song-card:hover {
  transform: translateX(4px);
  border-color: #fde68a;
  box-shadow: 0 8px 28px rgba(245, 158, 11, 0.15);
}

.hub-song-card:focus-visible {
  outline: 3px solid var(--warm);
  outline-offset: 2px;
}

.hub-song-icon {
  flex-shrink: 0;
  width: 2.5rem;
  height: 2.5rem;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 12px;
  background: linear-gradient(145deg, #fef3c7, #fde68a);
  color: #b45309;
  font-size: 1.1rem;
  font-weight: 700;
}

.hub-song-body {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
}

.hub-song-title {
  font-size: 0.98rem;
  font-weight: 700;
  color: var(--text);
}

.hub-song-desc {
  font-size: 0.8rem;
  color: var(--muted);
  line-height: 1.35;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.hub-song-meta {
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--accent);
  margin-top: 0.1rem;
}

.hub-song-arrow {
  flex-shrink: 0;
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--muted);
  transition: transform 0.2s, color 0.2s;
}

.hub-song-card:hover .hub-song-arrow {
  transform: translateX(3px);
  color: var(--warm);
}

.hub-songs-loading,
.hub-songs-empty {
  text-align: center;
  padding: 1.5rem;
  color: var(--muted);
  font-size: 0.88rem;
  background: var(--surface);
  border-radius: var(--radius-sm);
  border: 1px dashed var(--border);
}

/* ── Footer ── */

.hub-footer {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.25rem;
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
}

.hub-footer-brand {
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--muted);
}

.hub-footer-note {
  font-size: 0.75rem;
  color: #94a3b8;
}

/* ── Legacy / unused hub toolbar (keep for compat) ── */

.hub-toolbar,
.filter-group,
.empty-state,
.toast,
.hub-songs-link {
  display: none;
}

.lesson-card.locked {
  opacity: 0.72;
}

@media (min-width: 560px) {
  .hub-wrap {
    max-width: 560px;
    padding: 2rem 1.5rem 4rem;
  }
}

@media (max-width: 380px) {
  .continue-banner {
    flex-direction: column;
    align-items: stretch;
    text-align: center;
  }

  .btn-continue {
    width: 100%;
  }
}