:root {
  --bg: #f4f7fb;
  --surface: #ffffff;
  --surface-soft: #f8fbff;
  --text: #18212f;
  --muted: #5a6778;
  --line: #dce4ef;
  --primary: #2864f0;
  --primary-dark: #1743aa;
  --accent: #7c4dff;
  --shadow: 0 18px 40px rgba(19, 31, 56, 0.08);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: "Pretendard", "Noto Sans KR", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.65;
}

a { color: inherit; text-decoration: none; }
.container { width: min(1160px, calc(100% - 40px)); margin: 0 auto; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(220, 228, 239, 0.8);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  min-height: 72px;
}
.logo {
  font-size: 22px;
  font-weight: 800;
  color: var(--primary-dark);
}
.main-nav {
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
}
.main-nav a {
  color: var(--muted);
  font-weight: 600;
}
.main-nav a:hover { color: var(--primary); }

.hero {
  background: linear-gradient(135deg, #0f172a, #1f4fd8 70%, #7c4dff);
  color: white;
  padding: 92px 0 76px;
}
.hero-inner {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 28px;
  align-items: center;
}
.eyebrow,
.section-kicker {
  display: inline-block;
  font-size: 12px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  font-weight: 800;
}
.eyebrow { color: #c7d8ff; margin-bottom: 14px; }
.hero h1 {
  margin: 0 0 16px;
  font-size: clamp(34px, 4.2vw, 58px);
  line-height: 1.12;
}
.lead,
.detail-lead {
  margin: 0;
  color: rgba(255,255,255,0.88);
  max-width: 720px;
}
.hero-actions {
  display: flex;
  gap: 12px;
  margin-top: 28px;
  flex-wrap: wrap;
}
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 48px;
  padding: 0 18px;
  border-radius: 999px;
  font-weight: 700;
}
.btn-primary {
  background: white;
  color: var(--primary-dark);
}
.btn-secondary {
  background: rgba(255,255,255,0.12);
  border: 1px solid rgba(255,255,255,0.22);
  color: white;
}
.hero-panel {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 14px;
}
.info-card {
  background: rgba(255,255,255,0.92);
  color: var(--text);
  border-radius: 20px;
  padding: 22px;
  box-shadow: var(--shadow);
}
.info-card.wide { grid-column: 1 / -1; }
.info-card span {
  display: block;
  color: var(--muted);
  font-size: 13px;
  margin-bottom: 6px;
}
.info-card strong {
  font-size: 24px;
  line-height: 1.3;
}

.section { padding: 80px 0; }
.section.alt { background: var(--surface-soft); }
.section-head { text-align: center; margin-bottom: 28px; }
.section-head h2 { margin: 10px 0 10px; font-size: clamp(28px, 3vw, 42px); }
.section-head p { color: var(--muted); max-width: 760px; margin: 0 auto; }
.section-kicker { color: var(--primary); }

.recent-lecture-list {
  display: grid;
  gap: 16px;
  margin-bottom: 18px;
}
.recent-lecture-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  background: var(--surface);
  border-radius: 22px;
  padding: 26px 28px;
  box-shadow: var(--shadow);
  border: 1px solid rgba(220, 228, 239, 0.65);
  transition: transform 0.18s ease, box-shadow 0.18s ease;
}
.recent-lecture-item:hover {
  transform: translateY(-3px);
  box-shadow: 0 22px 42px rgba(19, 31, 56, 0.12);
}
.recent-lecture-copy {
  min-width: 0;
}
.recent-lecture-kicker {
  margin: 0 0 10px;
  font-size: 12px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--primary);
  font-weight: 800;
}
.recent-lecture-item strong {
  display: block;
  font-size: 24px;
  margin-bottom: 8px;
  color: var(--primary-dark);
}
.recent-lecture-item span {
  display: block;
  color: var(--muted);
  max-width: 760px;
}
.recent-lecture-link {
  font-style: normal;
  white-space: nowrap;
  color: var(--primary-dark);
  font-weight: 800;
}
.course-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 18px;
}
.single-course-grid {
  grid-template-columns: 1fr;
}
.course-card {
  background: var(--surface);
  border-radius: 24px;
  padding: 26px;
  box-shadow: var(--shadow);
  border: 1px solid rgba(220, 228, 239, 0.65);
  transition: transform 0.18s ease, box-shadow 0.18s ease;
}
.course-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 24px 50px rgba(19, 31, 56, 0.12);
}
.course-card.featured {
  background: linear-gradient(180deg, #eef4ff, #ffffff);
  border-color: #b7caf7;
}
.course-badge {
  display: inline-block;
  padding: 6px 10px;
  border-radius: 999px;
  background: rgba(40, 100, 240, 0.1);
  color: var(--primary);
  font-size: 12px;
  font-weight: 800;
  margin-bottom: 14px;
}
.course-card h3 { margin: 0 0 10px; }
.course-card p { color: var(--muted); margin: 0 0 18px; }
.course-link {
  color: var(--primary-dark);
  font-weight: 700;
}

.two-col {
  display: grid;
  grid-template-columns: 1fr 0.9fr;
  gap: 22px;
  align-items: start;
}
.feature-box {
  background: var(--surface);
  border-radius: 22px;
  padding: 24px;
  box-shadow: var(--shadow);
}
.feature-box ul { margin: 0; padding-left: 18px; }
.feature-box li + li { margin-top: 10px; }

.detail-hero {
  background: linear-gradient(135deg, #17203a, #214bbf);
  color: white;
  padding: 72px 0 56px;
}
.detail-hero h1 {
  margin: 8px 0 14px;
  font-size: clamp(30px, 4vw, 52px);
  line-height: 1.15;
}
.meta-row {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 22px;
}
.meta-row span {
  display: inline-flex;
  align-items: center;
  min-height: 36px;
  padding: 0 14px;
  border-radius: 999px;
  background: rgba(255,255,255,0.14);
  font-size: 14px;
}

.detail-section { padding-top: 54px; }
.detail-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 300px;
  gap: 24px;
}
.detail-main,
.detail-side {
  display: grid;
  gap: 20px;
}
.content-card,
.side-card,
.ad-box,
.video-wrap {
  background: var(--surface);
  border-radius: 24px;
  box-shadow: var(--shadow);
  border: 1px solid rgba(220, 228, 239, 0.7);
}
.content-card,
.side-card {
  padding: 24px;
}
.content-card h2,
.side-card h3 {
  margin-top: 0;
}
.ad-box {
  min-height: 120px;
  padding: 18px 20px 20px;
  display: flex;
  flex-direction: column;
  align-items: stretch;
  justify-content: center;
  color: var(--muted);
  background: linear-gradient(180deg, #ffffff, #f6f9ff);
  font-weight: 700;
  gap: 12px;
}
.ad-box .adsbygoogle {
  width: 100%;
}
.ad-label {
  font-size: 11px;
  letter-spacing: 0.14em;
  color: #7b8798;
  font-weight: 800;
}
.ad-box-top {
  min-height: 140px;
}
.ad-box-inline,
.ad-box-bottom {
  min-height: 160px;
}
.ad-box-side {
  min-height: 280px;
  position: sticky;
  top: 92px;
}
.video-wrap {
  padding: 16px;
}
.video-wrap iframe {
  width: 100%;
  aspect-ratio: 16 / 9;
  border: 0;
  border-radius: 16px;
}
.lecture-video-card {
  padding: 20px;
}
.lecture-video {
  width: 100%;
  aspect-ratio: 16 / 9;
  display: block;
  border-radius: 18px;
  background: #0f172a;
  outline: none;
}
.lecture-video-card video::-internal-media-controls-download-button {
  display: none;
}
.lecture-video-card video::-webkit-media-controls-enclosure {
  overflow: hidden;
}
.video-info-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  padding-top: 16px;
}
.video-info-bar h2 {
  margin: 0 0 8px;
  font-size: 24px;
}
.video-info-bar p {
  margin: 0;
  color: var(--muted);
}
.video-note {
  display: inline-flex;
  align-items: center;
  min-height: 36px;
  padding: 0 14px;
  border-radius: 999px;
  background: rgba(40, 100, 240, 0.08);
  color: var(--primary-dark);
  font-size: 13px;
  font-weight: 700;
  white-space: nowrap;
}
.curriculum-list,
.bullet-list {
  margin: 0;
  padding-left: 20px;
}
.curriculum-list li + li,
.bullet-list li + li { margin-top: 10px; }
.side-card ul {
  list-style: none;
  padding: 0;
  margin: 0;
}
.side-card li + li { margin-top: 10px; }
.side-card a { color: var(--primary-dark); font-weight: 600; }

.site-footer {
  background: #101726;
  color: rgba(255,255,255,0.78);
  padding: 28px 0;
}
.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}
.footer-inner strong { color: white; display: block; margin-bottom: 4px; }

@media (max-width: 1024px) {
  .hero-inner,
  .course-grid,
  .two-col,
  .detail-grid {
    grid-template-columns: 1fr;
  }
  .ad-box-side {
    position: static;
    top: auto;
    min-height: 140px;
  }
}

@media (max-width: 720px) {
  .container { width: min(100% - 28px, 1160px); }
  .header-inner,
  .footer-inner { flex-direction: column; align-items: flex-start; }
  .main-nav { gap: 12px; }
  .hero { padding: 78px 0 62px; }
  .section { padding: 64px 0; }
  .hero-panel { grid-template-columns: 1fr; }
  .btn { width: 100%; }
  .video-info-bar {
    flex-direction: column;
    align-items: flex-start;
  }
  .recent-lecture-item {
    flex-direction: column;
    align-items: flex-start;
  }
}