:root {
  color-scheme: light dark;
  --page: #f6f7fa;
  --card: #fff;
  --ink: #162440;
  --muted: #56647a;
  --line: #dce2eb;
  --accent: #2257a3;
  --soft: #eaf0fa;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* {
  box-sizing: border-box;
}
body {
  margin: 0;
  background: var(--page);
  color: var(--ink);
}
.course {
  max-width: 1080px;
  margin: 0 auto;
  padding: 64px 32px 40px;
}
.course-header {
  padding-bottom: 38px;
  border-bottom: 1px solid var(--line);
}
.course-meta {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 16px;
  color: var(--muted);
  font-size: 14px;
}
.course-code {
  padding: 7px 10px;
  border: 1px solid var(--line);
  border-radius: 6px;
  color: var(--accent);
  font-weight: 700;
  letter-spacing: 0.06em;
}
h1 {
  margin: 24px 0 16px;
  font-size: clamp(36px, 5.5vw, 58px);
  font-weight: 650;
  line-height: 1.12;
  letter-spacing: -0.035em;
}
.course-byline {
  margin: 0;
  color: var(--muted);
  font-size: 15px;
  line-height: 1.7;
}
.course-byline span {
  padding: 0 5px;
}
.section-heading {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  margin: 32px 0 18px;
}
.section-heading h2 {
  margin: 0;
  font-size: 20px;
  font-weight: 650;
}
.section-heading > span {
  color: var(--muted);
  font-size: 14px;
  font-variant-numeric: tabular-nums;
}
.lecture-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
  padding: 0;
  margin: 0;
  list-style: none;
}
.lecture-grid li {
  min-width: 0;
}
.lecture-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  height: 100%;
  min-height: 178px;
  gap: 14px;
  padding: 24px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--card);
  color: var(--ink);
  text-decoration: none;
  transition:
    border-color 150ms ease,
    box-shadow 150ms ease;
}
.lecture-number {
  color: var(--muted);
  font-size: 12px;
  font-weight: 650;
  letter-spacing: 0.07em;
  text-transform: uppercase;
}
.lecture-title {
  margin: 0;
  font-size: 19px;
  line-height: 1.4;
  font-weight: 600;
  overflow-wrap: anywhere;
}
.lecture-action {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  margin-top: auto;
  color: var(--accent);
  font-size: 13px;
  font-weight: 600;
}
.lecture-card:hover {
  border-color: var(--accent);
  box-shadow: 0 3px 14px #1624400c;
}
.lecture-card:hover .lecture-action {
  text-decoration: underline;
  text-underline-offset: 3px;
}
.lecture-card:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
  background: var(--soft);
}
.course-footer {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 8px 24px;
  margin-top: 28px;
  padding-top: 22px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 13px;
  line-height: 1.7;
}
.course-footer p {
  margin: 0;
}
kbd {
  padding: 1px 5px;
  border: 1px solid var(--line);
  border-radius: 4px;
  background: var(--card);
  font: inherit;
  font-size: 12px;
}

@media (max-width: 640px) {
  .course {
    padding: 32px 20px 28px;
  }
  .course-header {
    padding-bottom: 28px;
  }
  .lecture-grid {
    grid-template-columns: 1fr;
    gap: 12px;
  }
  .lecture-card {
    min-height: 148px;
    padding: 20px;
  }
  .lecture-title {
    font-size: 18px;
  }
}

@media (prefers-color-scheme: dark) {
  :root {
    --page: #111722;
    --card: #192230;
    --ink: #edf2fa;
    --muted: #acb9cd;
    --line: #354258;
    --accent: #9bbfff;
    --soft: #202f46;
  }
}

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