:root {
  color-scheme: dark;
  --bg: #06111d;
  --bg-soft: #0a1928;
  --surface: #0d2032;
  --surface-2: #10283d;
  --line: rgba(148, 184, 212, 0.16);
  --line-strong: rgba(88, 205, 255, 0.3);
  --text: #e9f3f9;
  --muted: #9eb2c2;
  --accent: #4fd1ff;
  --accent-2: #24e0b8;
  --accent-dark: #061923;
  --warning: #ffbf69;
  --code: #061019;
  --shadow: 0 24px 70px rgba(0, 0, 0, 0.35);
  --header-h: 72px;
  --content-w: 860px;
}

[data-theme="light"] {
  color-scheme: light;
  --bg: #f4f8fb;
  --bg-soft: #eaf2f7;
  --surface: #ffffff;
  --surface-2: #edf6fb;
  --line: rgba(20, 61, 87, 0.14);
  --line-strong: rgba(0, 135, 190, 0.28);
  --text: #102a3b;
  --muted: #567083;
  --accent: #007dab;
  --accent-2: #008b70;
  --accent-dark: #eefbff;
  --warning: #9b5b00;
  --code: #0c1c27;
  --shadow: 0 22px 60px rgba(28, 65, 88, 0.14);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--header-h) + 24px); }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); }
button, input { font: inherit; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }

.reading-progress { position: fixed; z-index: 100; inset: 0 0 auto; height: 3px; background: transparent; }
.reading-progress span { display: block; width: 0; height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent-2)); }

.site-header {
  position: sticky;
  z-index: 50;
  top: 0;
  height: var(--header-h);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 clamp(20px, 4vw, 64px);
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  backdrop-filter: blur(18px);
}

.brand { display: flex; align-items: center; gap: 12px; color: var(--text); text-decoration: none; }
.brand-mark { display: grid; width: 38px; height: 38px; place-items: center; color: var(--accent); }
.brand-mark svg { width: 100%; fill: none; stroke: currentColor; stroke-width: 2; }
.brand strong, .brand small { display: block; line-height: 1.25; }
.brand strong { letter-spacing: .08em; }
.brand small { color: var(--muted); font-size: .72rem; }
.header-actions { display: flex; gap: 8px; }
.icon-button { width: 42px; height: 42px; display: grid; place-items: center; border: 1px solid var(--line); border-radius: 50%; color: var(--text); background: var(--surface); cursor: pointer; }
.icon-button:hover { border-color: var(--line-strong); color: var(--accent); transform: translateY(-1px); }
.icon-button svg { width: 19px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; }
.moon-icon { display: none; }
[data-theme="light"] .sun-icon { display: none; }
[data-theme="light"] .moon-icon { display: block; }

.hero {
  position: relative;
  min-height: 560px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(400px, .9fr);
  align-items: center;
  gap: clamp(40px, 7vw, 100px);
  padding: 80px clamp(24px, 6vw, 96px);
  overflow: hidden;
  border-bottom: 1px solid var(--line);
  background: radial-gradient(circle at 72% 25%, rgba(31, 177, 224, .15), transparent 30%), linear-gradient(135deg, var(--bg), var(--bg-soft));
}
.hero-grid { position: absolute; inset: 0; opacity: .18; background-image: linear-gradient(var(--line) 1px, transparent 1px), linear-gradient(90deg, var(--line) 1px, transparent 1px); background-size: 48px 48px; mask-image: linear-gradient(to bottom, black, transparent 85%); }
.hero-content, .network-card { position: relative; z-index: 1; }
.eyebrow { color: var(--accent-2); font-size: .78rem; font-weight: 800; letter-spacing: .16em; }
.hero h1 { margin: 18px 0; font-size: clamp(3rem, 6vw, 5.8rem); line-height: .95; letter-spacing: -.055em; }
.hero h1 span { color: transparent; -webkit-text-stroke: 1px var(--accent); }
.hero p { max-width: 620px; color: var(--muted); font-size: clamp(1rem, 1.6vw, 1.2rem); }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 30px; }
.primary-button, .secondary-button { display: inline-flex; align-items: center; justify-content: center; min-height: 48px; padding: 0 20px; border-radius: 10px; font-weight: 750; text-decoration: none; }
.primary-button { color: #03202c; background: linear-gradient(135deg, var(--accent), var(--accent-2)); }
.secondary-button { color: var(--text); border: 1px solid var(--line-strong); background: var(--surface); }
.hero-stats { display: flex; flex-wrap: wrap; gap: 28px; margin: 36px 0 0; }
.hero-stats div { padding-left: 13px; border-left: 2px solid var(--accent); }
.hero-stats dt { color: var(--muted); font-size: .7rem; text-transform: uppercase; letter-spacing: .12em; }
.hero-stats dd { margin: 2px 0 0; font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-weight: 700; }

.network-card { width: min(100%, 520px); margin: 0; justify-self: center; overflow: hidden; border: 1px solid var(--line-strong); border-radius: 24px; background: rgba(9, 27, 42, .72); box-shadow: var(--shadow); backdrop-filter: blur(12px); }
.network-card img { display: block; width: 100%; height: auto; aspect-ratio: 16 / 9; object-fit: cover; }
[data-theme="light"] .network-card { background: rgba(255,255,255,.8); }
.network-zone { padding: 18px 20px; border: 1px solid var(--line); border-radius: 14px; background: color-mix(in srgb, var(--surface) 88%, transparent); }
.network-zone > strong { display: block; margin: 5px 0 14px; font-family: ui-monospace, SFMono-Regular, Consolas, monospace; color: var(--accent); }
.zone-label { font-size: .69rem; font-weight: 850; letter-spacing: .15em; color: var(--muted); }
.node { display: inline-flex; align-items: center; gap: 9px; margin-right: 20px; font-size: .78rem; line-height: 1.3; color: var(--muted); }
.node b { color: var(--text); font-family: ui-monospace, SFMono-Regular, Consolas, monospace; }
.node-dot { width: 11px; height: 11px; border: 2px solid var(--accent-2); border-radius: 50%; box-shadow: 0 0 12px var(--accent-2); }
.tunnel { text-align: center; color: var(--accent-2); font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-size: .75rem; letter-spacing: .12em; }
.tunnel small { color: var(--muted); letter-spacing: 0; }
.tunnel-line { display: flex; align-items: center; justify-content: center; gap: 18px; height: 20px; margin: 2px 0; border-top: 1px dashed var(--accent-2); transform: translateY(10px); }
.tunnel-line i { width: 6px; height: 6px; border-radius: 50%; background: var(--accent-2); box-shadow: 0 0 10px var(--accent-2); animation: pulse 1.8s infinite; }
.tunnel-line i:nth-child(2) { animation-delay: .4s; }.tunnel-line i:nth-child(3) { animation-delay: .8s; }
@keyframes pulse { 0%,100% { opacity: .25; transform: scale(.8); } 50% { opacity: 1; transform: scale(1.25); } }

.page-shell { display: grid; grid-template-columns: 300px minmax(0, 1fr); max-width: 1440px; margin: 0 auto; }
.sidebar { position: sticky; top: var(--header-h); height: calc(100vh - var(--header-h)); padding: 32px 24px; overflow: auto; border-right: 1px solid var(--line); }
.sidebar-heading { display: flex; align-items: center; justify-content: space-between; margin-bottom: 15px; color: var(--muted); font-size: .68rem; font-weight: 850; letter-spacing: .16em; }
.close-sidebar { display: none; color: var(--text); background: none; border: 0; font-size: 1.8rem; cursor: pointer; }
#table-of-contents a { display: block; padding: 7px 10px; border-left: 2px solid transparent; color: var(--muted); text-decoration: none; font-size: .83rem; line-height: 1.35; }
#table-of-contents a:hover, #table-of-contents a.active { color: var(--accent); border-left-color: var(--accent); background: linear-gradient(90deg, color-mix(in srgb, var(--accent) 10%, transparent), transparent); }
#table-of-contents a.toc-major { margin-top: 14px; color: var(--text); font-weight: 750; }

.content-column { min-width: 0; padding: 58px clamp(24px, 6vw, 84px) 80px; }
.markdown-body { width: min(100%, var(--content-w)); margin: 0 auto; }
.markdown-body h1, .markdown-body h2, .markdown-body h3 { scroll-margin-top: calc(var(--header-h) + 24px); line-height: 1.2; letter-spacing: -.025em; }
.markdown-body h1 { margin: 0 0 32px; font-size: clamp(2.2rem, 4vw, 3.6rem); }
.markdown-body h2 { margin: 72px 0 20px; padding-top: 8px; font-size: clamp(1.55rem, 2.5vw, 2.15rem); border-top: 1px solid var(--line); }
.markdown-body h3 { margin-top: 36px; font-size: 1.25rem; }
.markdown-body p, .markdown-body li { color: color-mix(in srgb, var(--text) 86%, var(--muted)); }
.markdown-body p:has(> img) { text-align: center; }
.markdown-body p > img { display: inline-block; width: min(100%, 560px); height: auto; border: 1px solid var(--line); border-radius: 14px; box-shadow: 0 12px 32px rgba(0,0,0,.14); }
.markdown-body strong { color: var(--text); }
.markdown-body hr { height: 1px; margin: 64px 0; border: 0; background: var(--line); }
.markdown-body blockquote { margin: 24px 0; padding: 14px 18px; border-left: 3px solid var(--warning); border-radius: 0 8px 8px 0; background: color-mix(in srgb, var(--warning) 8%, var(--surface)); }
.markdown-body blockquote p { margin: 0; }
.markdown-body :not(pre) > code { padding: 2px 6px; border: 1px solid var(--line); border-radius: 5px; color: var(--accent-2); background: var(--surface-2); font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-size: .88em; }
.markdown-body table { display: block; width: 100%; margin: 24px 0; overflow-x: auto; border-collapse: collapse; }
.markdown-body th, .markdown-body td { padding: 12px 14px; border: 1px solid var(--line); text-align: left; vertical-align: top; }
.markdown-body th { color: var(--accent); background: var(--surface-2); }
.markdown-body tr:nth-child(even) { background: color-mix(in srgb, var(--surface) 55%, transparent); }

.code-wrap { position: relative; margin: 24px 0; border: 1px solid var(--line); border-radius: 12px; overflow: hidden; background: var(--code); box-shadow: 0 12px 32px rgba(0,0,0,.16); }
.code-toolbar { height: 38px; display: flex; align-items: center; justify-content: space-between; padding: 0 9px 0 14px; border-bottom: 1px solid rgba(255,255,255,.08); color: #8199a9; font: 700 .68rem/1 ui-monospace, SFMono-Regular, Consolas, monospace; text-transform: uppercase; letter-spacing: .1em; }
.copy-button { padding: 6px 9px; border: 0; border-radius: 6px; color: #b9cbd6; background: rgba(255,255,255,.08); cursor: pointer; font-size: .68rem; }
.copy-button:hover { color: white; background: rgba(79,209,255,.2); }
.code-wrap pre { margin: 0; padding: 18px; overflow: auto; }
.code-wrap code { color: #d7e7ef; font: .84rem/1.65 ui-monospace, SFMono-Regular, Consolas, monospace; white-space: pre; }
.code-wrap .comment { color: #7092a5; }

.loading-state { min-height: 320px; display: grid; place-items: center; align-content: center; color: var(--muted); }
.loader { width: 32px; height: 32px; border: 3px solid var(--line); border-top-color: var(--accent); border-radius: 50%; animation: spin .7s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
.notice { width: min(100%, var(--content-w)); margin: 0 auto 24px; padding: 14px 18px; border: 1px solid color-mix(in srgb, var(--warning) 50%, var(--line)); border-radius: 10px; color: var(--warning); background: color-mix(in srgb, var(--warning) 8%, var(--surface)); }
.mobile-menu { display: none; align-items: center; gap: 6px; margin-bottom: 24px; padding: 8px 12px; color: var(--text); border: 1px solid var(--line); border-radius: 8px; background: var(--surface); }
.mobile-menu span { display: block; width: 14px; height: 1px; background: currentColor; }
.lesson-slides { width: min(100%, var(--content-w)); margin: 88px auto 0; padding-top: 32px; border-top: 1px solid var(--line); }
.slides-heading { display: flex; align-items: flex-end; justify-content: space-between; gap: 24px; margin-bottom: 24px; }
.slides-heading h2 { margin: 10px 0 8px; font-size: clamp(1.7rem, 3vw, 2.35rem); letter-spacing: -.025em; }
.slides-heading p { max-width: 680px; margin: 0; color: var(--muted); }
.slides-count { flex: 0 0 auto; padding: 7px 10px; border: 1px solid var(--line); border-radius: 999px; color: var(--accent-2); background: var(--surface-2); font: 700 .72rem/1 ui-monospace, SFMono-Regular, Consolas, monospace; }
.slides-preview { position: relative; display: block; overflow: hidden; width: min(100%, 900px); margin: 0 auto; border: 1px solid var(--line-strong); border-radius: 16px; background: var(--surface-2); box-shadow: var(--shadow); }
.slides-preview img { display: block; width: 100%; height: auto; aspect-ratio: 16 / 9; object-fit: cover; transition: transform .25s ease; }
.slides-preview span { position: absolute; right: 18px; bottom: 18px; padding: 9px 13px; border: 1px solid rgba(255,255,255,.22); border-radius: 9px; color: white; background: rgba(2, 12, 21, .82); backdrop-filter: blur(8px); font-size: .8rem; font-weight: 750; }
.slides-preview:hover img { transform: scale(1.012); }
.slides-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 20px; }
.content-footer { width: min(100%, var(--content-w)); margin: 72px auto 0; padding-top: 24px; display: flex; justify-content: space-between; gap: 20px; border-top: 1px solid var(--line); color: var(--muted); font-size: .83rem; }

.search-dialog { position: fixed; z-index: 90; inset: 0; padding: 12vh 20px; background: rgba(1, 9, 15, .74); backdrop-filter: blur(8px); }
.search-panel { max-width: 720px; margin: 0 auto; overflow: hidden; border: 1px solid var(--line-strong); border-radius: 16px; background: var(--surface); box-shadow: var(--shadow); }
.search-input-row { display: flex; align-items: center; gap: 12px; padding: 14px 16px; border-bottom: 1px solid var(--line); }
.search-input-row svg { width: 21px; fill: none; stroke: var(--accent); stroke-width: 2; }
.search-input-row input { flex: 1; min-width: 0; border: 0; outline: 0; color: var(--text); background: transparent; font-size: 1.02rem; }
.search-input-row kbd { padding: 3px 7px; border: 1px solid var(--line); border-radius: 5px; color: var(--muted); background: var(--bg-soft); font-size: .7rem; }
.search-results { max-height: 55vh; padding: 10px; overflow: auto; }
.search-results > p { padding: 10px; color: var(--muted); }
.search-result { display: block; padding: 12px 14px; border-radius: 9px; color: var(--text); text-decoration: none; }
.search-result:hover { background: var(--surface-2); }
.search-result strong { display: block; color: var(--accent); }
.search-result span { display: block; margin-top: 3px; color: var(--muted); font-size: .8rem; }
.toast { position: fixed; z-index: 110; right: 22px; bottom: 22px; padding: 10px 15px; border: 1px solid var(--line-strong); border-radius: 9px; color: var(--text); background: var(--surface); box-shadow: var(--shadow); opacity: 0; transform: translateY(12px); pointer-events: none; transition: .2s ease; }
.toast.show { opacity: 1; transform: translateY(0); }

@media (max-width: 980px) {
  .hero { grid-template-columns: 1fr; padding-top: 60px; }
  .network-card { min-height: 0; }
  .page-shell { grid-template-columns: 1fr; }
  .sidebar { position: fixed; z-index: 80; top: 0; left: 0; width: min(88vw, 330px); height: 100vh; padding-top: 24px; background: var(--surface); transform: translateX(-105%); transition: transform .25s ease; box-shadow: var(--shadow); }
  .sidebar.open { transform: translateX(0); }
  .close-sidebar, .mobile-menu { display: flex; }
  .content-column { padding-top: 28px; }
}

@media (max-width: 620px) {
  :root { --header-h: 64px; }
  .site-header { padding: 0 16px; }
  .brand small { display: none; }
  .hero { min-height: auto; padding: 52px 20px; }
  .hero h1 { font-size: 3.1rem; }
  .network-card { min-height: 0; }
  .node { margin-right: 8px; font-size: .72rem; }
  .content-column { padding: 24px 18px 60px; }
  .markdown-body h2 { margin-top: 56px; }
  .slides-heading { align-items: flex-start; flex-direction: column; }
  .slides-preview span { right: 10px; bottom: 10px; }
  .content-footer { flex-direction: column; }
}

@media print {
  .site-header, .hero, .sidebar, .mobile-menu, .reading-progress, .copy-button, .search-dialog, .toast, .lesson-slides { display: none !important; }
  .page-shell { display: block; }
  .content-column { padding: 0; }
  .markdown-body { width: 100%; }
  body { color: #111; background: white; }
  .markdown-body p, .markdown-body li { color: #222; }
  .code-wrap { break-inside: avoid; box-shadow: none; }
}