:root {
  --bg: #ffffff;
  --text: #1d1d1d;
  --muted: #5c5c5c;
  --line: #d9d9d9;
  --soft: #f7f7f7;
  --accent: #1f5f8b;
  --accent-dark: #174767;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Georgia, "Times New Roman", serif;
  line-height: 1.6;
}

code {
  font-family: Consolas, "Courier New", monospace;
  font-size: 0.95em;
}

.page-shell {
  width: min(860px, calc(100% - 2rem));
  margin: 0 auto;
  padding: 3rem 0 4rem;
}

.site-header {
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--line);
}

.eyebrow,
.lecture-label {
  margin: 0;
  color: var(--muted);
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1,
h2,
h3 {
  margin: 0;
  font-weight: 600;
  line-height: 1.15;
}

h1 {
  margin-top: 0.5rem;
  font-size: clamp(2.2rem, 5vw, 3.4rem);
}

h2 {
  font-size: clamp(1.5rem, 3vw, 2rem);
}

h3 {
  font-size: 1.35rem;
}

.lede,
.course-meta p,
.description-block p,
.section-block p,
.section-heading p,
.lecture-summary,
.file-hint {
  margin: 0;
}

.lede {
  max-width: 40rem;
  margin-top: 0.9rem;
  color: var(--muted);
  font-size: 1.05rem;
}

.course-meta {
  margin-top: 1.5rem;
}

.course-meta p + p {
  margin-top: 0.35rem;
}

.course-meta span {
  display: inline-block;
  min-width: 6.5rem;
  color: var(--muted);
  font-weight: 700;
}

.description-block,
.section-block,
.section-heading {
  margin-top: 2rem;
}

.description-block p,
.section-block p,
.section-heading p {
  margin-top: 0.75rem;
  color: var(--muted);
}

.info-list {
  margin-top: 0.75rem;
}

.info-list p + p {
  margin-top: 0.5rem;
}

.info-list span {
  display: inline-block;
  min-width: 8.5rem;
  color: var(--text);
  font-weight: 700;
}

.info-list a {
  color: var(--accent);
  text-decoration: none;
}

.info-list a:hover,
.info-list a:focus-visible {
  color: var(--accent-dark);
  text-decoration: underline;
}

.lecture-grid {
  margin-top: 0.5rem;
  border-top: 1px solid var(--line);
}

.lecture-card {
  padding: 1.4rem 0;
  border-bottom: 1px solid var(--line);
}

.lecture-card h3 {
  margin-top: 0.35rem;
}

.lecture-summary {
  margin-top: 0.55rem;
  color: var(--muted);
}

.file-hint {
  margin-top: 0.75rem;
  padding: 0.7rem 0.85rem;
  background: var(--soft);
  border-left: 3px solid var(--line);
  color: var(--muted);
  font-size: 0.95rem;
}

.lecture-links {
  display: flex;
  gap: 0.75rem;
  margin-top: 0.9rem;
}

.lecture-links a {
  color: var(--accent);
  font-weight: 600;
  text-decoration: none;
}

.lecture-links a:hover,
.lecture-links a:focus-visible {
  color: var(--accent-dark);
  text-decoration: underline;
}

@media (max-width: 640px) {
  .page-shell {
    width: min(100% - 1rem, 860px);
    padding-top: 1.75rem;
  }

  .course-meta span {
    display: block;
    min-width: auto;
  }

  .info-list span {
    display: block;
    min-width: auto;
  }

  .lecture-links {
    flex-direction: column;
    gap: 0.35rem;
  }
}