/* Classroom hub — landing / course picker */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

:root {
  --ink: #0f172a;
  --ink-soft: #334155;
  --paper: #f1f5f9;
  --card: #ffffff;
  --line: #e2e8f0;
  --line-strong: #cbd5e1;
  --muted: #64748b;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --accent-soft: #eff6ff;
  --accent-ring: rgba(37, 99, 235, .18);
  --ok: #15803d;
  --ok-soft: #ecfdf5;
  --warn: #b45309;
  --warn-soft: #fffbeb;
  --header-h: 60px;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow-sm: 0 1px 2px rgba(15, 23, 42, .05);
  --shadow: 0 1px 3px rgba(15, 23, 42, .06), 0 8px 24px rgba(15, 23, 42, .06);
  --shadow-lg: 0 4px 6px rgba(15, 23, 42, .04), 0 20px 40px rgba(15, 23, 42, .08);
}

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

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: 'Inter', 'Segoe UI', system-ui, sans-serif;
  background: var(--paper);
  color: var(--ink-soft);
  font-size: 14px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  overflow: auto;
  min-height: 100vh;
}

button, input { font: inherit; }

/* ---- Header ---- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  height: var(--header-h);
  background: rgba(255, 255, 255, .92);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--line);
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 0 28px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: inherit;
}

.logo-mark {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  background: linear-gradient(135deg, #2563eb 0%, #1d4ed8 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  box-shadow: 0 2px 8px rgba(37, 99, 235, .35);
}

.brand-text h1 {
  margin: 0;
  font-size: 16px;
  font-weight: 700;
  letter-spacing: -.02em;
  color: var(--ink);
  line-height: 1.2;
}

.brand-sub {
  font-size: 11px;
  color: var(--muted);
  font-weight: 500;
}

.header-spacer { flex: 1; min-width: 8px; }

.site-nav {
  display: flex;
  align-items: center;
  flex-wrap: nowrap;
  gap: 4px;
  flex-shrink: 0;
}

.site-nav a {
  color: var(--muted);
  font-size: 13px;
  font-weight: 500;
  text-decoration: none;
  padding: 8px 14px;
  border-radius: var(--radius-sm);
  transition: background .15s, color .15s;
  white-space: nowrap;
}

.site-nav a:hover { background: var(--paper); color: var(--ink); }

.site-nav a.active {
  background: var(--accent-soft);
  color: var(--accent);
}

.nav-primary {
  background: var(--accent) !important;
  color: #fff !important;
  box-shadow: 0 1px 2px rgba(37, 99, 235, .25);
}

.nav-primary:hover {
  background: var(--accent-hover) !important;
  color: #fff !important;
}

/* ---- Page ---- */
.hub-main {
  max-width: 960px;
  margin: 0 auto;
  padding: 36px 24px 64px;
}

.hub-hero {
  text-align: center;
  margin-bottom: 36px;
}

.hub-hero-icon {
  width: 56px;
  height: 56px;
  margin: 0 auto 18px;
  border-radius: 14px;
  background: var(--accent-soft);
  color: var(--accent);
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--accent-ring);
}

.hub-hero h2 {
  margin: 0 0 10px;
  font-size: 28px;
  font-weight: 700;
  letter-spacing: -.03em;
  color: var(--ink);
}

.hub-hero p {
  margin: 0 auto;
  max-width: 520px;
  color: var(--muted);
  font-size: 15px;
  line-height: 1.55;
}

.hub-hero p a {
  color: var(--accent);
  font-weight: 500;
  text-decoration: none;
}

.hub-hero p a:hover { text-decoration: underline; }

.hub-toolbar {
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
  margin-bottom: 20px;
}

.hub-toolbar .search-wrap {
  flex: 1;
  min-width: 200px;
  position: relative;
}

.hub-toolbar .search-wrap svg {
  position: absolute;
  left: 12px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--muted);
  pointer-events: none;
}

.hub-toolbar input[type=search] {
  width: 100%;
  padding: 10px 12px 10px 38px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius-sm);
  background: #fff;
  font-size: 14px;
  color: var(--ink);
}

.hub-toolbar input[type=search]:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-ring);
}

.count-badge {
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
  white-space: nowrap;
}

.count-badge strong { color: var(--ink); }

/* ---- Open by ID panel ---- */
.open-panel {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 20px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 28px;
  display: flex;
  gap: 12px;
  align-items: flex-end;
  flex-wrap: wrap;
}

.open-panel label {
  display: block;
  font-size: 12px;
  font-weight: 600;
  color: var(--ink-soft);
  margin-bottom: 6px;
}

.open-panel .field { flex: 1; min-width: 200px; }

.open-panel input {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--line-strong);
  border-radius: var(--radius-sm);
  font-size: 14px;
  background: #fff;
  color: var(--ink);
}

.open-panel input:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-ring);
}

.open-panel button {
  border: 0;
  background: var(--accent);
  color: #fff;
  padding: 10px 20px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  box-shadow: 0 1px 2px rgba(37, 99, 235, .2);
}

.open-panel button:hover { background: var(--accent-hover); }

/* ---- Course grid ---- */
.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 14px;
}

.section-head h3 {
  margin: 0;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--muted);
}

.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 14px;
}

.course-card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 18px 16px;
  box-shadow: var(--shadow-sm);
  transition: border-color .15s, box-shadow .15s, transform .15s;
  display: flex;
  flex-direction: column;
  gap: 12px;
  min-height: 140px;
}

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

.course-card-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 10px;
}

.course-card h4 {
  margin: 0;
  font-size: 15px;
  font-weight: 700;
  color: var(--ink);
  line-height: 1.35;
  letter-spacing: -.01em;
}

.course-card .meta {
  font-size: 12px;
  color: var(--muted);
  line-height: 1.45;
}

.pill {
  display: inline-block;
  font-size: 10px;
  font-weight: 600;
  padding: 3px 9px;
  border-radius: 999px;
  text-transform: lowercase;
  white-space: nowrap;
  flex-shrink: 0;
}

.pill.ok { background: var(--ok-soft); color: var(--ok); }
.pill.warn { background: var(--warn-soft); color: var(--warn); }
.pill.neutral { background: var(--paper); color: var(--muted); }

.course-card-actions {
  display: flex;
  gap: 8px;
  margin-top: auto;
}

.course-card-actions a,
.course-card-actions button {
  flex: 1;
  text-align: center;
  padding: 9px 12px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  border: 1px solid var(--line-strong);
  background: #fff;
  color: var(--ink-soft);
}

.course-card-actions a.play {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.course-card-actions a.play:hover { background: var(--accent-hover); color: #fff; }

.course-card-actions a.secondary:hover {
  background: var(--paper);
  color: var(--ink);
}

.course-card-actions button.danger {
  background: #fff;
  color: #b91c1c;
  border: 1px solid #fecaca;
}

.course-card-actions button.danger:hover:not(:disabled) {
  background: #fef2f2;
}

.confirm-overlay {
  position: fixed;
  inset: 0;
  z-index: 80;
  background: rgba(15, 23, 42, .45);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  backdrop-filter: blur(4px);
}

.confirm-overlay[hidden] { display: none !important; }

.confirm-box {
  width: min(420px, 96vw);
  background: #fff;
  border-radius: 14px;
  padding: 22px;
  box-shadow: var(--shadow-lg);
}

.confirm-box h3 { margin: 0 0 8px; color: var(--ink); font-size: 18px; }
.confirm-body { margin: 0 0 18px; color: var(--muted); font-size: 13px; line-height: 1.5; }

.confirm-actions {
  display: flex;
  justify-content: flex-end;
  gap: 8px;
}

.confirm-actions button {
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  padding: 8px 14px;
  background: #fff;
  cursor: pointer;
}

.confirm-actions button.danger {
  background: #b91c1c;
  border-color: #b91c1c;
  color: #fff;
}

.confirm-actions button.danger:hover { background: #991b1b; }

/* ---- Empty / loading ---- */
.empty-panel {
  background: var(--card);
  border: 1px dashed var(--line-strong);
  border-radius: var(--radius);
  padding: 40px 24px;
  text-align: center;
  color: var(--muted);
}

.empty-panel strong {
  display: block;
  font-size: 15px;
  color: var(--ink);
  margin-bottom: 6px;
}

.empty-panel p {
  margin: 0;
  font-size: 13px;
  line-height: 1.5;
}

.empty-panel a {
  color: var(--accent);
  font-weight: 500;
  text-decoration: none;
}

.empty-panel a:hover { text-decoration: underline; }

.hub-footer {
  margin-top: 40px;
  text-align: center;
  font-size: 13px;
}

.hub-footer a {
  color: var(--muted);
  text-decoration: none;
  font-weight: 500;
}

.hub-footer a:hover { color: var(--accent); }

@media (max-width: 640px) {
  .site-header { padding: 0 16px; }
  .hub-main { padding: 24px 16px 48px; }
  .hub-hero h2 { font-size: 22px; }
  .open-panel { flex-direction: column; align-items: stretch; }
  .course-grid { grid-template-columns: 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  .course-card { transition: none; }
  .course-card:hover { transform: none; }
}