/* ── Design Tokens ─────────────────────────────── */
:root {
  --bg:           #ffffff;
  --bg-surface:   #f8f9fc;
  --bg-sidebar:   #f0f2f8;
  --bg-card:      #ffffff;
  --border:       #e2e6f0;
  --border-focus: #4f6ef7;
  --accent:       #4f6ef7;
  --accent-light: #eef1fe;
  --accent-2:     #7c5cfc;
  --accent-3:     #0ea5e9;
  --text-primary: #0f172a;
  --text-secondary:#475569;
  --text-muted:   #94a3b8;
  --sidebar-w:    280px;
  --header-h:     64px;
  --radius:       12px;
  --radius-sm:    8px;
  --shadow-sm:    0 1px 3px rgba(15,23,42,0.08), 0 1px 2px rgba(15,23,42,0.04);
  --shadow:       0 4px 16px rgba(15,23,42,0.08), 0 1px 4px rgba(15,23,42,0.04);
  --shadow-lg:    0 12px 40px rgba(15,23,42,0.1), 0 4px 12px rgba(15,23,42,0.06);
  --transition:   0.2s cubic-bezier(0.4,0,0.2,1);
}

/* ── Reset ─────────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  font-family: 'Inter', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text-primary);
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* ── Header ────────────────────────────────────── */
header {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--header-h);
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  padding: 0 1.5rem;
  gap: 1rem;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}

.header-logo {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
}

.logo-mark {
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  box-shadow: 0 2px 8px rgba(79,110,247,0.3);
}

.logo-mark svg { display: block; }

.logo-text {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 0.9375rem;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.2;
}

.logo-sub {
  font-size: 0.68rem;
  color: var(--text-muted);
  font-weight: 400;
  font-family: 'Inter', sans-serif;
}

.header-spacer { flex: 1; }

.header-badge {
  background: var(--accent-light);
  border: 1px solid rgba(79,110,247,0.2);
  color: var(--accent);
  font-size: 0.7rem;
  font-weight: 700;
  padding: 0.28rem 0.75rem;
  border-radius: 999px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

/* Hamburger */
.menu-toggle {
  display: none;
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  padding: 0.45rem;
  color: var(--text-secondary);
  align-items: center;
  justify-content: center;
  transition: var(--transition);
}
.menu-toggle:hover { background: var(--bg-surface); }
.menu-toggle svg { display: block; }

/* ── Layout ────────────────────────────────────── */
.app-shell {
  display: grid;
  grid-template-columns: var(--sidebar-w) 1fr;
  height: calc(100vh - var(--header-h));
  margin-top: var(--header-h);
  position: relative;
}

/* ── Sidebar ───────────────────────────────────── */
.sidebar {
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  padding-bottom: 2rem;
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}

.sidebar::-webkit-scrollbar { width: 4px; }
.sidebar::-webkit-scrollbar-track { background: transparent; }
.sidebar::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

.sidebar-section { padding: 1.25rem 0.75rem 0.25rem; }

.sidebar-section-label {
  font-size: 0.625rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-muted);
  padding: 0 0.5rem 0.6rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.sidebar-section-label::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--border);
}

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

/* Nav item */
.nav-item {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  padding: 0.6rem 0.75rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
  border: 1px solid transparent;
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 0.8375rem;
  font-weight: 500;
}

.nav-item:hover {
  background: #fff;
  color: var(--text-primary);
  border-color: var(--border);
  box-shadow: var(--shadow-sm);
}

.nav-item.active {
  background: #fff;
  color: var(--accent);
  border-color: rgba(79,110,247,0.25);
  box-shadow: var(--shadow-sm);
}

.nav-item-icon {
  width: 30px;
  height: 30px;
  border-radius: 7px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: var(--transition);
}

/* Icon color variants */
.ic-blue   { background: #eff6ff; color: #3b82f6; }
.ic-violet { background: #f5f3ff; color: #7c3aed; }
.ic-cyan   { background: #ecfeff; color: #0891b2; }
.ic-green  { background: #f0fdf4; color: #16a34a; }
.ic-rose   { background: #fff1f2; color: #e11d48; }
.ic-amber  { background: #fffbeb; color: #d97706; }
.ic-indigo { background: #eef2ff; color: #4338ca; }
.ic-sky    { background: #f0f9ff; color: #0284c7; }
.ic-purple { background: #faf5ff; color: #9333ea; }
.ic-orange { background: #fff7ed; color: #ea580c; }

.nav-item-icon svg { display: block; }

.nav-item-label {
  flex: 1;
  line-height: 1.3;
  min-width: 0;
}
.nav-item-label small {
  display: block;
  font-size: 0.67rem;
  color: var(--text-muted);
  font-weight: 400;
  margin-top: 1px;
}

.nav-item-chevron {
  flex-shrink: 0;
  color: var(--text-muted);
  opacity: 0;
  transform: translateX(-4px);
  transition: var(--transition);
}
.nav-item:hover .nav-item-chevron,
.nav-item.active .nav-item-chevron {
  opacity: 1;
  transform: translateX(0);
  color: var(--accent);
}

/* ── Viewer pane ───────────────────────────────── */
.viewer {
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background: var(--bg);
}

.viewer-toolbar {
  display: none;
  align-items: center;
  gap: 0.75rem;
  padding: 0.7rem 1.25rem;
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}
.viewer-toolbar.visible { display: flex; }

.viewer-breadcrumb {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.78rem;
  color: var(--text-muted);
  flex: 1;
  min-width: 0;
}
.crumb-sep { color: var(--border); }
.crumb-current {
  color: var(--text-secondary);
  font-weight: 500;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.viewer-btn {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  font-size: 0.775rem;
  font-weight: 500;
  padding: 0.4rem 0.8rem;
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
  white-space: nowrap;
  font-family: 'Inter', sans-serif;
}
.viewer-btn:hover {
  background: var(--accent-light);
  border-color: rgba(79,110,247,0.3);
  color: var(--accent);
}
.viewer-btn svg { display: block; }

.content-frame {
  display: none;
  flex: 1;
  border: none;
  width: 100%;
  height: 100%;
  background: var(--bg-surface);
}
.content-frame.visible { display: block; }

/* ── Welcome screen ────────────────────────────── */
.welcome-screen {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 3rem 2.5rem 4rem;
  gap: 2rem;
  overflow-y: auto;
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
  background: var(--bg);
}

/* Hero illustration area */
.hero-block {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.25rem;
  max-width: 520px;
  text-align: center;
}

.hero-illustration {
  width: 220px;
  height: 160px;
  flex-shrink: 0;
}

.welcome-title {
  font-family: 'Space Grotesk', sans-serif;
  font-size: clamp(1.6rem, 2.8vw, 2.2rem);
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.2;
  letter-spacing: -0.02em;
}

.welcome-title span {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.welcome-desc {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  max-width: 440px;
  line-height: 1.7;
}

/* Divider */
.welcome-divider {
  width: 100%;
  max-width: 760px;
  display: flex;
  align-items: center;
  gap: 1rem;
  color: var(--text-muted);
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.welcome-divider::before,
.welcome-divider::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--border);
}

/* Quick cards */
.quick-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 0.875rem;
  width: 100%;
  max-width: 760px;
}

.quick-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem 1rem;
  cursor: pointer;
  transition: var(--transition);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.75rem;
  text-align: center;
  box-shadow: var(--shadow-sm);
}

.quick-card:hover {
  border-color: rgba(79,110,247,0.3);
  box-shadow: var(--shadow-lg);
  transform: translateY(-3px);
}

.qc-icon-wrap {
  width: 44px;
  height: 44px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.qc-icon-wrap svg { display: block; }

.qc-label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-secondary);
}

/* Video section */
.videos-section {
  width: 100%;
  max-width: 760px;
}

.section-heading {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 0.875rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-align: left;
}
.section-heading svg { color: var(--accent); }

.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(230px, 1fr));
  gap: 0.875rem;
}

.video-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: var(--transition);
  box-shadow: var(--shadow-sm);
}

.video-card:hover {
  border-color: rgba(79,110,247,0.25);
  box-shadow: var(--shadow);
  transform: translateY(-2px);
}

.video-card iframe {
  width: 100%;
  aspect-ratio: 16/9;
  display: block;
  border: none;
}

.video-label {
  padding: 0.6rem 0.8rem;
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--text-secondary);
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  gap: 0.4rem;
}
.video-label svg { color: var(--accent); flex-shrink: 0; }

/* ── Mobile overlay ────────────────────────────── */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(15,23,42,0.4);
  backdrop-filter: blur(4px);
  z-index: 90;
}
.sidebar-overlay.open { display: block; }

/* ── Animations ────────────────────────────────── */
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(18px); }
  to   { opacity: 1; transform: translateY(0); }
}

.hero-block      { animation: fadeUp 0.5s ease both 0s; }
.welcome-divider { animation: fadeUp 0.5s ease both 0.1s; }
.quick-cards     { animation: fadeUp 0.5s ease both 0.15s; }
.videos-section  { animation: fadeUp 0.5s ease both 0.22s; }

/* ── Responsive ────────────────────────────────── */
@media (max-width: 768px) {
  .app-shell { grid-template-columns: 1fr; }
  .menu-toggle { display: flex; }

  .sidebar {
    position: fixed;
    top: var(--header-h);
    left: 0; bottom: 0;
    width: var(--sidebar-w);
    max-width: 88vw;
    z-index: 95;
    transform: translateX(-100%);
    transition: transform var(--transition);
    box-shadow: var(--shadow-lg);
  }
  .sidebar.open { transform: translateX(0); }

  .welcome-screen { padding: 2rem 1rem 3rem; }
  .quick-cards { grid-template-columns: repeat(2, 1fr); }
  .video-grid { grid-template-columns: 1fr; }
}