:root {
  --bg: #f6f8ff;
  --surface: #ffffff;
  --text: #0f172a;
  --muted: #64748b;
  --line: #e2e8f0;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --secondary: #7c3aed;
  --green: #059669;
  --orange: #ea580c;
  --shadow: 0 24px 70px rgba(15, 23, 42, 0.12);
  --radius-xl: 34px;
  --radius-lg: 26px;
  --radius-md: 18px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Pretendard, Roboto, sans-serif;
  color: var(--text);
  background:
    radial-gradient(circle at top left, rgba(37, 99, 235, 0.12), transparent 32rem),
    radial-gradient(circle at top right, rgba(124, 58, 237, 0.10), transparent 30rem),
    var(--bg);
  line-height: 1.6;
}

a { color: inherit; text-decoration: none; }
button, input, select, textarea { font: inherit; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  border-bottom: 1px solid rgba(226, 232, 240, 0.78);
  background: rgba(255, 255, 255, 0.84);
  backdrop-filter: blur(18px);
}

.header-inner {
  max-width: 1200px;
  height: 76px;
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  gap: 26px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 900;
  letter-spacing: -0.04em;
  white-space: nowrap;
}
.brand-mark {
  width: 38px;
  height: 38px;
  display: inline-grid;
  place-items: center;
  border-radius: 14px;
  color: white;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  box-shadow: 0 12px 28px rgba(37, 99, 235, 0.25);
}

.main-nav { flex: 1; }
.main-nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
}
.nav-link {
  display: inline-flex;
  align-items: center;
  border: 0;
  border-radius: 13px;
  padding: 12px 13px;
  color: #334155;
  background: transparent;
  font-weight: 800;
  cursor: pointer;
  white-space: nowrap;
}
.nav-link:hover,
.nav-link.active,
.nav-link[aria-current="page"] {
  color: var(--primary);
  background: #eff6ff;
}

.header-cta, .btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  border: 0;
  border-radius: 999px;
  font-weight: 900;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease, background 0.2s ease;
}
.header-cta {
  padding: 11px 18px;
  color: white;
  background: var(--primary);
  box-shadow: 0 12px 26px rgba(37, 99, 235, 0.24);
  white-space: nowrap;
}
.header-cta:hover, .btn:hover { transform: translateY(-2px); }

.mobile-menu-button {
  display: none;
  margin-left: auto;
  width: 44px;
  height: 44px;
  border: 1px solid var(--line);
  border-radius: 14px;
  background: white;
  padding: 9px;
}
.mobile-menu-button span {
  display: block;
  height: 2px;
  margin: 5px 0;
  border-radius: 4px;
  background: var(--text);
}

.mega-panel {
  position: absolute;
  left: 0;
  right: 0;
  top: 76px;
  min-height: 422px;
  padding: 30px 0 36px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(-8px);
  transition: opacity 0.2s ease, transform 0.2s ease, visibility 0.2s ease;
  pointer-events: none;
  overflow: hidden;
  border-top: 1px solid rgba(226, 232, 240, 0.72);
  border-bottom: 1px solid rgba(226, 232, 240, 0.86);
  background:
    linear-gradient(90deg, rgba(238, 245, 255, 0.96), rgba(245, 243, 255, 0.8) 46%, rgba(236, 253, 245, 0.86)),
    url("assets/mega-menu-bg.svg");
  background-size: cover;
  background-position: center;
  box-shadow: 0 34px 90px rgba(15, 23, 42, 0.18);
}
.mega-panel::before {
  content: "";
  position: absolute;
  inset: 0;
  background:
    radial-gradient(circle at 16% 24%, rgba(37, 99, 235, 0.16), transparent 22rem),
    radial-gradient(circle at 78% 18%, rgba(124, 58, 237, 0.14), transparent 20rem),
    linear-gradient(180deg, rgba(255, 255, 255, 0.20), rgba(255, 255, 255, 0.56));
  pointer-events: none;
}
.mega-panel::after {
  content: "AI PROFESSOR";
  position: absolute;
  left: max(24px, calc((100vw - 1200px) / 2));
  bottom: -40px;
  color: rgba(15, 23, 42, 0.045);
  font-size: clamp(72px, 9vw, 156px);
  font-weight: 950;
  letter-spacing: -0.08em;
  line-height: 1;
  white-space: nowrap;
  pointer-events: none;
}
.mega-panel.open {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
  pointer-events: auto;
}
.mega-inner {
  position: relative;
  z-index: 1;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}
.mega-menu-table {
  display: grid;
  grid-template-columns: repeat(6, minmax(0, 1fr));
  gap: 12px;
}
.mega-column {
  overflow: hidden;
  min-height: 326px;
  border: 1px solid rgba(226, 232, 240, 0.82);
  border-radius: 24px;
  background: rgba(255, 255, 255, 0.72);
  backdrop-filter: blur(14px);
  box-shadow: 0 18px 42px rgba(15, 23, 42, 0.09);
}
.mega-column-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  min-height: 64px;
  padding: 18px 16px;
  border-bottom: 1px solid rgba(226, 232, 240, 0.84);
  background: rgba(255, 255, 255, 0.74);
  color: var(--text);
  font-size: 17px;
  font-weight: 950;
  letter-spacing: -0.035em;
}
.mega-column-title::after {
  content: "→";
  color: var(--primary);
  font-size: 15px;
  opacity: 0.75;
}
.mega-column-body {
  display: grid;
  gap: 6px;
  padding: 10px;
}
.mega-subitem {
  display: grid;
  gap: 2px;
  padding: 10px;
  border-radius: 14px;
  transition: background 0.18s ease, transform 0.18s ease;
}
.mega-subitem:hover,
.mega-subitem:focus-visible {
  background: rgba(239, 246, 255, 0.94);
  outline: none;
  transform: translateY(-1px);
}
.mega-subitem strong {
  color: #1e293b;
  font-size: 14px;
  line-height: 1.35;
  letter-spacing: -0.02em;
}
.mega-subitem span {
  color: var(--muted);
  font-size: 12px;
  line-height: 1.45;
}
.accent-column .mega-column-title {
  color: white;
  border-bottom-color: rgba(255, 255, 255, 0.22);
  background: linear-gradient(135deg, var(--primary), var(--secondary));
}
.accent-column .mega-column-title::after { color: white; }

.mobile-panel { display: none; }

.page-hero, .home-hero {
  max-width: 1200px;
  margin: 0 auto;
  padding: 82px 24px 64px;
  display: grid;
  grid-template-columns: 1.02fr 0.98fr;
  align-items: center;
  gap: 54px;
}
.home-hero { min-height: calc(100vh - 76px); }
.eyebrow {
  margin: 0 0 13px;
  color: var(--primary);
  font-size: 13px;
  font-weight: 950;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}
h1, .section h2, .cta-card h2 {
  margin: 0;
  line-height: 1.05;
  letter-spacing: -0.065em;
}
h1 { font-size: clamp(42px, 5.6vw, 72px); }
.section h2, .cta-card h2 { font-size: clamp(34px, 4.2vw, 52px); }
.hero-desc, .lead {
  max-width: 650px;
  margin: 24px 0 30px;
  color: var(--muted);
  font-size: 19px;
}
.hero-actions { display: flex; gap: 12px; flex-wrap: wrap; }
.btn { padding: 14px 22px; }
.btn.primary {
  color: white;
  background: var(--primary);
  box-shadow: 0 14px 30px rgba(37, 99, 235, 0.28);
}
.btn.secondary {
  color: var(--text);
  background: white;
  border: 1px solid var(--line);
}
.btn.small { padding: 12px 18px; }

.hero-visual {
  position: relative;
  min-height: 540px;
  display: grid;
  place-items: center;
}
.hero-visual::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: 46px;
  background: url("assets/hero-orbit.svg") center / contain no-repeat;
  filter: drop-shadow(0 28px 70px rgba(15, 23, 42, 0.12));
}
.ai-card {
  position: relative;
  z-index: 1;
  width: min(430px, 92%);
  padding: 28px;
  border: 1px solid rgba(255,255,255,0.82);
  border-radius: 34px;
  background: rgba(255,255,255,0.86);
  backdrop-filter: blur(18px);
  box-shadow: var(--shadow);
}
.ai-card-top { display: flex; align-items: center; gap: 8px; color: var(--muted); font-weight: 800; font-size: 13px; }
.ai-card-top span { width: 10px; height: 10px; border-radius: 50%; background: #cbd5e1; }
.ai-card h3 { margin: 24px 0 10px; font-size: 28px; letter-spacing: -0.045em; }
.ai-card p { color: var(--muted); margin: 0; }
.ai-chip-row { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 24px; }
.ai-chip-row span { padding: 8px 11px; border-radius: 999px; background: #eff6ff; color: #1d4ed8; font-weight: 850; font-size: 13px; }

.section {
  max-width: 1200px;
  margin: 0 auto;
  padding: 84px 24px;
}
.section-heading { max-width: 760px; margin-bottom: 34px; }
.section-heading p:not(.eyebrow), .muted { color: var(--muted); font-size: 18px; }
.card-grid { display: grid; gap: 18px; }
.card-grid.three { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.card-grid.two { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.feature-card, .info-card, .step-card, .contact-form, .page-panel {
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: rgba(255,255,255,0.9);
  box-shadow: 0 16px 44px rgba(15, 23, 42, 0.06);
}
.feature-card, .info-card, .step-card { padding: 26px; }
.feature-card:hover, .info-card:hover { transform: translateY(-3px); box-shadow: 0 24px 58px rgba(15, 23, 42, 0.10); }
.icon {
  width: 50px;
  height: 50px;
  display: grid;
  place-items: center;
  border-radius: 17px;
  background: #eff6ff;
  font-size: 24px;
}
.feature-card h3, .info-card h3, .step-card h3 { margin: 18px 0 8px; font-size: 22px; letter-spacing: -0.04em; }
.feature-card p, .info-card p, .step-card p { margin: 0; color: var(--muted); }
.feature-card ul, .info-card ul, .page-panel ul { margin: 16px 0 0; padding-left: 18px; color: #334155; font-weight: 700; }

.split {
  display: grid;
  grid-template-columns: 0.95fr 1.05fr;
  gap: 42px;
  align-items: start;
}
.page-panel {
  padding: 30px;
  background:
    radial-gradient(circle at top left, rgba(37, 99, 235, 0.12), transparent 20rem),
    white;
}
.flow-list { display: grid; gap: 14px; margin-top: 22px; }
.flow-item {
  display: grid;
  grid-template-columns: 44px 1fr;
  gap: 14px;
  align-items: start;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: rgba(255,255,255,0.72);
}
.flow-item b {
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  border-radius: 15px;
  color: white;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
}
.flow-item strong { display: block; font-size: 18px; letter-spacing: -0.03em; }
.flow-item span { color: var(--muted); }

.band {
  max-width: none;
  color: white;
  background: #0f172a;
}
.band .section-heading, .band .card-grid { max-width: 1200px; margin-left: auto; margin-right: auto; }
.band .section-heading p:not(.eyebrow) { color: #cbd5e1; }
.band .feature-card { background: linear-gradient(135deg, rgba(255,255,255,0.12), rgba(255,255,255,0.04)); border-color: rgba(255,255,255,0.13); }
.band .feature-card p { color: #cbd5e1; }
.band .feature-card h3 { color: white; }

.cta {
  max-width: 1200px;
  margin: 0 auto;
  padding: 54px 24px 92px;
}
.cta-card {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 24px;
  align-items: center;
  padding: 38px;
  border: 1px solid var(--line);
  border-radius: 34px;
  background:
    radial-gradient(circle at top left, rgba(37, 99, 235, 0.18), transparent 25rem),
    white;
  box-shadow: var(--shadow);
}
.cta-card p { margin: 14px 0 0; color: var(--muted); font-size: 18px; }

.contact-layout {
  max-width: 1200px;
  margin: 0 auto;
  padding: 70px 24px 100px;
  display: grid;
  grid-template-columns: 0.9fr 1.1fr;
  gap: 42px;
}
.contact-form { display: grid; gap: 14px; padding: 30px; }
.contact-form label { display: grid; gap: 7px; color: #334155; font-weight: 850; }
.contact-form input, .contact-form select, .contact-form textarea {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 13px 14px;
  background: white;
  color: var(--text);
  outline: none;
}
.contact-form input:focus, .contact-form select:focus, .contact-form textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.1);
}
.form-message { min-height: 24px; margin: 0; color: var(--primary); font-weight: 900; }

.footer {
  max-width: 1200px;
  margin: 0 auto;
  padding: 28px 24px 40px;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  border-top: 1px solid var(--line);
  color: #475569;
}
.footer p { margin: 4px 0 0; }

.section-reveal { opacity: 0; transform: translateY(22px); transition: 0.7s ease; }
.section-reveal.visible { opacity: 1; transform: translateY(0); }

@media (max-width: 1080px) {
  .mega-menu-table { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .mega-panel { min-height: 720px; }
}

@media (max-width: 980px) {
  .mobile-menu-button { display: block; }
  .main-nav, .header-cta, .mega-panel { display: none; }
  .header-inner { height: 70px; }

  .mobile-panel {
    display: block;
    position: absolute;
    left: 14px;
    right: 14px;
    top: 76px;
    max-height: calc(100vh - 94px);
    overflow: auto;
    padding: 14px;
    border: 1px solid rgba(226, 232, 240, 0.9);
    border-radius: 24px;
    background:
      linear-gradient(180deg, rgba(255,255,255,0.90), rgba(255,255,255,0.78)),
      url("assets/mega-menu-bg.svg") center / cover no-repeat;
    box-shadow: var(--shadow);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-8px);
    pointer-events: none;
    transition: 0.2s ease;
  }
  .site-header.menu-open .mobile-panel {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
    pointer-events: auto;
  }
  .mobile-section {
    overflow: hidden;
    border: 1px solid rgba(226, 232, 240, 0.86);
    border-radius: 18px;
    background: rgba(255,255,255,0.78);
    backdrop-filter: blur(10px);
  }
  .mobile-section + .mobile-section { margin-top: 10px; }
  .mobile-section-button {
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border: 0;
    padding: 16px;
    background: rgba(255,255,255,0.76);
    color: var(--text);
    font-weight: 950;
    text-align: left;
    cursor: pointer;
  }
  .mobile-section-button::after { content: "+"; color: var(--primary); font-size: 20px; }
  .mobile-section.open .mobile-section-button::after { content: "−"; }
  .mobile-submenu {
    display: none;
    padding: 8px 10px 12px;
  }
  .mobile-section.open .mobile-submenu { display: grid; gap: 6px; }
  .mobile-submenu a {
    display: grid;
    gap: 2px;
    padding: 11px 10px;
    border-radius: 14px;
  }
  .mobile-submenu a:hover { background: #eff6ff; }
  .mobile-submenu strong { font-size: 14px; }
  .mobile-submenu span { color: var(--muted); font-size: 12px; }
  .mobile-direct {
    display: flex;
    justify-content: center;
    margin-top: 12px;
    padding: 13px 16px;
    border-radius: 999px;
    color: white;
    background: var(--primary);
    font-weight: 950;
  }

  .home-hero, .page-hero, .split, .contact-layout, .cta-card { grid-template-columns: 1fr; }
  .home-hero, .page-hero { padding-top: 54px; }
  .hero-visual { min-height: 460px; }
  .card-grid.three, .card-grid.two { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 640px) {
  .header-inner { padding: 0 16px; }
  .brand { font-size: 18px; }
  .home-hero, .page-hero, .section, .cta, .contact-layout, .footer { padding-left: 16px; padding-right: 16px; }
  h1 { font-size: 42px; }
  .hero-desc, .lead { font-size: 17px; }
  .hero-actions { flex-direction: column; }
  .hero-visual { min-height: 390px; }
  .ai-card { width: 100%; }
  .card-grid.three, .card-grid.two { grid-template-columns: 1fr; }
  .cta-card, .contact-form { padding: 26px; border-radius: 26px; }
  .footer { flex-direction: column; }
}

.cta-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  justify-content: flex-end;
}
@media (max-width: 760px) {
  .cta-actions { justify-content: flex-start; }
}


/* Inline demo sections embedded in product pages */
.inline-demo .section-heading {
  max-width: 760px;
  margin-bottom: 28px;
}
.inline-demo .lead {
  margin-top: 12px;
}
.inline-demo .demo-grid {
  margin-top: 24px;
}
.inline-demo .demo-card h2 {
  margin-top: 0;
}
.inline-demo .demo-form button,
.demo-form button {
  border: 0;
  border-radius: 999px;
  padding: 14px 18px;
  color: #fff;
  background: linear-gradient(135deg, #2563eb, #7c3aed);
  font-weight: 950;
  cursor: pointer;
  box-shadow: 0 14px 34px rgba(37, 99, 235, 0.22);
}
.inline-demo .demo-form button:hover,
.demo-form button:hover {
  transform: translateY(-1px);
}


/* AI lecture video menu integration */
.mega-menu-table { grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); }
@media (min-width: 1180px) {
  .mega-menu-table { grid-template-columns: repeat(6, minmax(150px, 1fr)); }
}
@media (min-width: 981px) and (max-width: 1280px) {
  .header-inner { gap: 14px; }
  .nav-link { padding: 10px 9px; font-size: 14px; }
  .header-cta { padding: 10px 14px; }
}