:root {
  color-scheme: dark;
  --bg: #0b0d10;
  --surface: #111419;
  --surface-raised: #171b21;
  --line: #272c34;
  --line-soft: #1d2229;
  --text: #f1f3f5;
  --muted: #989fa9;
  --quiet: #6f7782;
  --accent: #91e6c3;
  --accent-strong: #b5f3d9;
  --accent-dim: rgba(145, 230, 195, 0.09);
  --max-width: 1180px;
  font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  font-synthesis: none;
  text-rendering: optimizeLegibility;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 88px; }
body { margin: 0; background: var(--bg); color: var(--text); line-height: 1.65; }
a { color: inherit; text-decoration: none; }
a:focus-visible, summary:focus-visible { outline: 2px solid var(--accent); outline-offset: 4px; border-radius: 4px; }
.skip-link { position: fixed; z-index: 100; left: 16px; top: -80px; padding: 10px 16px; color: var(--bg); background: var(--accent); border-radius: 8px; font-weight: 700; }
.skip-link:focus { top: 12px; }

.site-header {
  position: sticky; z-index: 20; top: 0;
  display: grid; grid-template-columns: 1fr auto 1fr; align-items: center;
  min-height: 68px; padding: 0 max(24px, calc((100vw - var(--max-width)) / 2));
  border-bottom: 1px solid rgba(39, 44, 52, 0.82);
  background: rgba(11, 13, 16, 0.88); backdrop-filter: blur(18px);
}
.brand { display: inline-flex; align-items: center; gap: 11px; width: max-content; font-weight: 650; letter-spacing: -0.02em; }
.brand-mark { display: grid; width: 32px; height: 32px; place-items: center; border: 1px solid #3a424d; border-radius: 9px; color: var(--accent); font-size: 0.74rem; letter-spacing: 0.06em; }
.site-nav { display: flex; gap: 28px; color: var(--muted); font-size: 0.89rem; }
.site-nav a, .home-link { transition: color 160ms ease; }
.site-nav a:hover, .home-link:hover { color: var(--text); }
.site-nav a[aria-current="page"] { color: var(--text); }
.home-link { justify-self: end; color: var(--muted); font-size: 0.88rem; }

main, .site-footer { width: min(calc(100% - 48px), var(--max-width)); margin-inline: auto; }
.hero { min-height: 460px; display: flex; align-items: center; padding: 104px 0 76px; border-bottom: 1px solid var(--line); }
.hero-copy { max-width: 760px; }
.eyebrow, .section-number, .course-code, .resource-type { margin: 0; color: var(--muted); font-size: 0.76rem; font-weight: 700; letter-spacing: 0.13em; text-transform: uppercase; }
.hero h1 { margin: 18px 0 20px; max-width: 760px; font-size: clamp(2.8rem, 5.5vw, 4.8rem); line-height: 1.04; letter-spacing: -0.05em; font-weight: 620; }
.hero-intro { max-width: 640px; margin: 0; color: var(--muted); font-size: clamp(1rem, 1.5vw, 1.17rem); }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 28px; }
.button { display: inline-flex; min-height: 44px; align-items: center; justify-content: center; padding: 0 18px; border: 1px solid var(--line); border-radius: 10px; font-size: 0.91rem; font-weight: 650; transition: transform 160ms ease, border-color 160ms ease, background 160ms ease; }
.button:hover { transform: translateY(-2px); border-color: #46505d; }
.button-primary { color: #07110d; border-color: var(--accent); background: var(--accent); }
.button-primary:hover { background: var(--accent-strong); }
.button-quiet { color: var(--muted); background: var(--surface); }

.course-index, .course-section { padding: 100px 0; border-bottom: 1px solid var(--line); }
.section-note { max-width: 320px; margin: 0; color: var(--muted); font-size: 0.88rem; text-align: right; }
.section-heading, .course-heading { display: flex; justify-content: space-between; gap: 40px; align-items: flex-end; margin-bottom: 42px; }
.section-heading h2, .course-heading h2 { margin: 8px 0 0; font-size: clamp(2.15rem, 5vw, 4.4rem); line-height: 1.08; letter-spacing: -0.045em; font-weight: 620; }
.course-heading p:not(.section-number) { max-width: 680px; margin: 16px 0 0; color: var(--muted); }
.course-cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; }
.course-card { min-height: 286px; display: flex; flex-direction: column; padding: 26px; border: 1px solid var(--line); border-radius: 18px; background: var(--surface); transition: border-color 160ms ease, transform 160ms ease, background 160ms ease; }
.course-card:hover { transform: translateY(-4px); border-color: #46505d; background: var(--surface-raised); }
.course-card h3 { margin: 64px 0 12px; font-size: 1.55rem; letter-spacing: -0.035em; }
.course-card p { margin: 0; color: var(--muted); font-size: 0.92rem; }
.card-meta { display: flex; justify-content: space-between; align-items: center; margin-top: auto; color: var(--muted); font-size: 0.8rem; }
.course-card-muted { background: transparent; }
.badge { display: inline-flex; width: max-content; padding: 5px 10px; border: 1px solid #3d454f; border-radius: 999px; color: var(--muted); font-size: 0.72rem; font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; }
.repo-link { flex: 0 0 auto; padding-bottom: 4px; border-bottom: 1px solid #4a535e; color: var(--muted); font-size: 0.9rem; }
.repo-link:hover { color: var(--text); border-color: var(--accent); }

.resource-group { margin-top: 58px; }
.compact-group { margin-top: 72px; }
.resource-group-title { display: flex; justify-content: space-between; align-items: baseline; margin-bottom: 20px; }
.resource-group-title h3 { margin: 0; font-size: 1.35rem; letter-spacing: -0.025em; }
.resource-group-title span { color: var(--quiet); font-size: 0.76rem; letter-spacing: 0.08em; text-transform: uppercase; }
.resource-grid { display: grid; grid-template-columns: 1.2fr 1fr 1fr; gap: 14px; }
.resource-grid-four { grid-template-columns: repeat(4, 1fr); }
.resource-card { min-height: 230px; display: flex; flex-direction: column; padding: 24px; border: 1px solid var(--line); border-radius: 14px; background: var(--surface); }
.resource-card-featured { border-color: rgba(145, 230, 195, 0.3); background: linear-gradient(145deg, var(--accent-dim), var(--surface) 72%); }
.resource-card h4 { margin: 32px 0 8px; font-size: 1.18rem; letter-spacing: -0.02em; }
.resource-card h3 { margin: 32px 0 8px; font-size: 1.18rem; letter-spacing: -0.02em; }
.resource-card > p:not(.resource-type) { margin: 0; color: var(--muted); font-size: 0.86rem; }
.resource-card a { width: max-content; margin-top: auto; color: var(--accent); font-size: 0.85rem; font-weight: 650; }
.resource-details { margin-top: 14px; border: 1px solid var(--line); border-radius: 14px; background: var(--surface); overflow: hidden; }
.resource-details summary { padding: 18px 22px; cursor: pointer; color: var(--muted); font-size: 0.9rem; font-weight: 650; list-style-position: inside; }
.resource-details[open] summary { color: var(--text); border-bottom: 1px solid var(--line); }
.link-list { display: grid; grid-template-columns: 1fr 1fr; }
.link-list a { display: flex; justify-content: space-between; gap: 22px; padding: 15px 22px; border-bottom: 1px solid var(--line-soft); color: var(--muted); font-size: 0.84rem; }
.link-list a:nth-last-child(-n+2) { border-bottom: 0; }
.link-list a:nth-child(odd) { border-right: 1px solid var(--line-soft); }
.link-list a:hover { color: var(--text); background: rgba(255,255,255,0.018); }
.link-list a span:last-child { color: var(--quiet); white-space: nowrap; }
.archive-table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: 14px; background: var(--surface); }
.archive-table { width: 100%; border-collapse: collapse; min-width: 680px; }
.archive-table th, .archive-table td { padding: 17px 20px; border-bottom: 1px solid var(--line-soft); text-align: left; font-size: 0.86rem; }
.archive-table thead th { color: var(--quiet); font-size: 0.7rem; letter-spacing: 0.1em; text-transform: uppercase; }
.archive-table tbody th { color: var(--muted); font-weight: 600; }
.archive-table tbody tr:last-child > * { border-bottom: 0; }
.archive-table a { color: var(--accent); }
.archive-table a:hover { text-decoration: underline; text-underline-offset: 3px; }
.number-grid { display: grid; grid-template-columns: repeat(13, 1fr); gap: 1px; background: var(--line); }
.number-grid a { display: grid; min-height: 58px; place-items: center; background: var(--surface); color: var(--muted); font-size: 0.8rem; font-variant-numeric: tabular-nums; transition: color 150ms ease, background 150ms ease; }
.number-grid a:hover { color: var(--accent); background: var(--surface-raised); }
.slide-grid { display: grid; grid-template-columns: repeat(5, 1fr); gap: 10px; }
.slide-grid article { min-height: 150px; padding: 18px; border: 1px solid var(--line); border-radius: 12px; background: var(--surface); }
.slide-grid article > span { color: var(--quiet); font-size: 0.68rem; font-weight: 700; letter-spacing: 0.1em; }
.slide-grid h4 { margin: 28px 0 8px; font-size: 1rem; }
.slide-grid h3 { margin: 28px 0 8px; font-size: 1rem; }
.slide-grid p { margin: 0; color: var(--muted); font-size: 0.78rem; }
.slide-grid a:hover { color: var(--accent); }

.upcoming-section { border-bottom: 0; }
.placeholder-table-wrap { opacity: 0.72; }
.placeholder-table td { min-width: 170px; height: 57px; background-image: linear-gradient(90deg, transparent, rgba(255,255,255,0.018), transparent); }
.placeholder-note { margin: 14px 0 0; color: var(--quiet); font-size: 0.8rem; }
.placeholder-note span { margin-right: 7px; color: var(--accent); }
.site-footer { display: grid; grid-template-columns: 1fr 2fr auto; gap: 24px; align-items: center; min-height: 150px; color: var(--quiet); font-size: 0.78rem; }
.site-footer p { margin: 0; }
.site-footer a:hover { color: var(--text); }
.not-found { min-height: 100vh; display: grid; align-content: center; justify-items: start; }
.not-found h1 { max-width: 760px; margin: 20px 0 12px; font-size: clamp(2.8rem, 8vw, 6rem); line-height: 1; letter-spacing: -0.055em; }
.not-found > p:not(.eyebrow) { margin: 0 0 30px; color: var(--muted); }

.course-page-hero { min-height: 430px; display: flex; flex-direction: column; justify-content: center; align-items: flex-start; padding: 86px 0 72px; border-bottom: 1px solid var(--line); }
.breadcrumb { margin-bottom: 54px; color: var(--quiet); font-size: 0.82rem; }
.breadcrumb:hover { color: var(--text); }
.course-page-hero h1 { max-width: 920px; margin: 16px 0 18px; font-size: clamp(2.8rem, 6vw, 5.2rem); line-height: 1.03; letter-spacing: -0.05em; font-weight: 620; }
.course-page-hero > p:not(.eyebrow) { max-width: 680px; margin: 0; color: var(--muted); font-size: 1rem; }
.course-page-hero .repo-link, .course-page-hero .badge { margin-top: 30px; }
.course-page-content { padding: 76px 0 100px; border-bottom: 1px solid var(--line); }
.course-page-content > .resource-group:first-child { margin-top: 0; }
.course-page-content > .priority-resource + .resource-group { margin-top: 0; }
.course-page-content > .resource-grid:first-child { margin-bottom: 14px; }
.course-page-content .resource-group-title h2 { margin: 0; font-size: 1.35rem; letter-spacing: -0.025em; }
.priority-resource { display: flex; justify-content: space-between; align-items: center; gap: 48px; margin-bottom: 72px; padding: 30px 32px; border: 1px solid rgba(145, 230, 195, 0.42); border-radius: 16px; background: linear-gradient(120deg, rgba(145, 230, 195, 0.12), var(--surface) 68%); }
.priority-resource h2 { margin: 10px 0 8px; font-size: clamp(1.55rem, 3vw, 2.25rem); line-height: 1.15; letter-spacing: -0.035em; }
.priority-resource > div > p:last-child { max-width: 660px; margin: 0; color: var(--muted); font-size: 0.9rem; }
.priority-resource .button { flex: 0 0 auto; }

@media (max-width: 980px) {
  .site-header { grid-template-columns: 1fr auto; }
  .site-nav { display: none; }
  .hero { min-height: 420px; }
  .course-page-hero { min-height: 390px; }
  .course-cards { grid-template-columns: 1fr; }
  .course-card { min-height: 220px; }
  .course-card h3 { margin-top: 42px; }
  .resource-grid, .resource-grid-four { grid-template-columns: repeat(2, 1fr); }
  .number-grid { grid-template-columns: repeat(7, 1fr); }
  .slide-grid { grid-template-columns: repeat(3, 1fr); }
}

@media (max-width: 680px) {
  .site-header { padding-inline: 18px; }
  .brand > span:last-child { display: none; }
  .home-link { font-size: 0.78rem; }
  main, .site-footer { width: min(calc(100% - 32px), var(--max-width)); }
  .hero { min-height: 390px; padding: 80px 0 62px; }
  .hero h1 { font-size: clamp(2.6rem, 11vw, 3.6rem); }
  .course-page-hero { min-height: 360px; padding: 64px 0 56px; }
  .course-page-hero h1 { font-size: clamp(2.55rem, 11vw, 3.7rem); }
  .breadcrumb { margin-bottom: 42px; }
  .course-index, .course-section { padding: 72px 0; }
  .course-page-content { padding: 60px 0 76px; }
  .priority-resource { display: block; margin-bottom: 56px; padding: 26px 24px; }
  .priority-resource .button { margin-top: 24px; }
  .section-note { margin-top: 16px; text-align: left; }
  .section-heading, .course-heading { display: block; }
  .repo-link, .course-heading > .badge { display: inline-flex; margin-top: 22px; }
  .resource-grid, .resource-grid-four { grid-template-columns: 1fr; }
  .link-list { grid-template-columns: 1fr; }
  .link-list a, .link-list a:nth-child(odd), .link-list a:nth-last-child(-n+2) { border-right: 0; border-bottom: 1px solid var(--line-soft); }
  .link-list a:last-child { border-bottom: 0; }
  .number-grid { grid-template-columns: repeat(5, 1fr); }
  .slide-grid { grid-template-columns: repeat(2, 1fr); }
  .site-footer { grid-template-columns: 1fr; align-content: center; padding: 30px 0; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition-duration: 0.01ms !important; }
}