:root {
  --bg: #0a0c0f;
  --bg-elev: #11151b;
  --bg-card: #161b23;
  --line: rgba(210, 168, 110, 0.16);
  --line-strong: rgba(210, 168, 110, 0.38);
  --copper: #d2a86e;
  --copper-hot: #e8c088;
  --solder: #3ecfbf;
  --solder-dim: #1a8f84;
  --ink: #f3eee4;
  --muted: #9a9388;
  --dim: #6d675f;
  --danger: #e07a5f;
  --ok: #7dce82;
  --shadow: 0 24px 60px rgba(0, 0, 0, 0.38);
  --radius: 14px;
  --max: 1180px;
  --serif: "Noto Serif SC", "Songti SC", serif;
  --sans: "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --mono: "IBM Plex Mono", "Consolas", monospace;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  font-family: var(--sans);
  color: var(--ink);
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(210, 168, 110, 0.08), transparent 55%),
    radial-gradient(900px 500px at 110% 0%, rgba(62, 207, 191, 0.06), transparent 50%),
    var(--bg);
  min-height: 100vh;
  line-height: 1.7;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(rgba(210, 168, 110, 0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(210, 168, 110, 0.035) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse at center, black 35%, transparent 80%);
  z-index: 0;
}

a { color: var(--copper); text-decoration: none; }
a:hover { color: var(--copper-hot); }

img { max-width: 100%; }

.wrap {
  width: min(var(--max), calc(100% - 40px));
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

/* drawing frame ticks */
.frame {
  position: relative;
}
.frame::before,
.frame::after {
  content: "";
  position: absolute;
  width: 18px;
  height: 18px;
  border: 1px solid var(--line-strong);
  pointer-events: none;
}
.frame::before { top: 10px; left: 10px; border-right: 0; border-bottom: 0; }
.frame::after { bottom: 10px; right: 10px; border-left: 0; border-top: 0; }

.nav {
  position: sticky;
  top: 0;
  z-index: 40;
  backdrop-filter: blur(16px);
  background: rgba(10, 12, 15, 0.72);
  border-bottom: 1px solid var(--line);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 72px;
  gap: 20px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  color: var(--ink);
}

.brand-mark {
  width: 36px;
  height: 36px;
  border: 1px solid var(--copper);
  display: grid;
  place-items: center;
  color: var(--copper);
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.08em;
}

.brand strong {
  display: block;
  font-family: var(--serif);
  font-size: 18px;
  font-weight: 700;
  letter-spacing: 0.04em;
}

.brand span {
  display: block;
  font-family: var(--mono);
  font-size: 10px;
  color: var(--muted);
  letter-spacing: 0.18em;
  text-transform: uppercase;
}

.nav-links {
  display: flex;
  gap: 16px;
  align-items: center;
  flex-wrap: wrap;
  justify-content: flex-end;
}

.nav-links a {
  color: var(--muted);
  font-size: 13px;
  letter-spacing: 0.04em;
  white-space: nowrap;
}

.nav-links a.active,
.nav-links a:hover {
  color: var(--ink);
}

.menu-btn {
  display: none;
  background: transparent;
  border: 1px solid var(--line-strong);
  color: var(--ink);
  padding: 8px 12px;
  font-family: var(--mono);
  font-size: 12px;
  cursor: pointer;
}

.hero {
  padding: 88px 0 48px;
}

.kicker {
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.22em;
  text-transform: uppercase;
  color: var(--solder);
}

h1, h2, h3, h4 {
  font-family: var(--serif);
  font-weight: 700;
  line-height: 1.25;
  margin: 0 0 12px;
}

h1 {
  font-size: clamp(42px, 7vw, 84px);
  letter-spacing: 0.02em;
  margin-top: 14px;
}

h2 { font-size: clamp(28px, 4vw, 40px); }
h3 { font-size: 22px; }

.lede {
  max-width: 680px;
  color: var(--muted);
  font-size: 18px;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 40px;
  align-items: end;
}

.meta-card {
  border: 1px solid var(--line);
  background: linear-gradient(180deg, rgba(22, 27, 35, 0.9), rgba(17, 21, 27, 0.7));
  padding: 22px;
  box-shadow: var(--shadow);
}

.meta-row {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  padding: 10px 0;
  border-bottom: 1px dashed var(--line);
  font-size: 13px;
}

.meta-row:last-child { border-bottom: 0; }
.meta-row span { color: var(--dim); font-family: var(--mono); }
.meta-row b { font-weight: 500; }

.actions {
  display: flex;
  gap: 12px;
  margin-top: 28px;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 18px;
  border: 1px solid var(--copper);
  color: var(--bg);
  background: var(--copper);
  font-family: var(--sans);
  font-size: 14px;
  cursor: pointer;
}

.btn.ghost {
  background: transparent;
  color: var(--copper);
}

.btn:hover { filter: brightness(1.08); }

.section {
  padding: 56px 0;
}

.section-head {
  display: flex;
  justify-content: space-between;
  align-items: end;
  gap: 20px;
  margin-bottom: 28px;
}

.section-head p {
  color: var(--muted);
  margin: 0;
  max-width: 520px;
}

.rev {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--dim);
  letter-spacing: 0.16em;
}

.cards {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 16px;
}

.card {
  display: block;
  background: var(--bg-card);
  border: 1px solid var(--line);
  padding: 22px 20px 20px;
  color: inherit;
  min-height: 210px;
  transition: transform 0.18s ease, border-color 0.18s ease;
  position: relative;
}

.card:hover {
  transform: translateY(-3px);
  border-color: var(--line-strong);
  color: inherit;
}

.card .ref {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--solder);
  letter-spacing: 0.14em;
}

.card h3 { margin-top: 18px; }
.card p { color: var(--muted); font-size: 14px; margin: 0; }

.flow {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 10px;
}

.flow-step {
  border: 1px solid var(--line);
  padding: 18px 16px;
  background: rgba(17, 21, 27, 0.8);
}

.flow-step b {
  display: block;
  font-family: var(--mono);
  font-size: 11px;
  color: var(--copper);
  margin-bottom: 8px;
}

.callout {
  border-left: 3px solid var(--copper);
  background: rgba(210, 168, 110, 0.06);
  padding: 16px 18px;
  margin: 22px 0;
}

.callout.warn {
  border-left-color: var(--danger);
  background: rgba(224, 122, 95, 0.08);
}

.article {
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 36px;
  padding: 48px 0 80px;
}

.toc {
  position: sticky;
  top: 96px;
  align-self: start;
  border: 1px solid var(--line);
  padding: 16px;
  background: rgba(17, 21, 27, 0.72);
}

.toc h4 {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.18em;
  color: var(--dim);
  margin-bottom: 10px;
}

.toc a {
  display: block;
  color: var(--muted);
  font-size: 13px;
  padding: 6px 0;
}

.toc a:hover { color: var(--ink); }

.prose h2 { margin-top: 42px; }
.prose h3 { margin-top: 28px; }
.prose p { color: #d4cfc6; }
.prose ul, .prose ol { color: #d4cfc6; padding-left: 18px; }
.prose li { margin: 8px 0; }
.prose code {
  font-family: var(--mono);
  font-size: 0.92em;
  color: var(--solder);
  background: rgba(62, 207, 191, 0.08);
  padding: 1px 6px;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin: 18px 0 28px;
  font-size: 14px;
}

th, td {
  border: 1px solid var(--line);
  padding: 10px 12px;
  text-align: left;
}

th {
  background: rgba(210, 168, 110, 0.08);
  font-weight: 600;
  color: var(--copper-hot);
}

.search {
  width: 100%;
  background: var(--bg-elev);
  border: 1px solid var(--line);
  color: var(--ink);
  padding: 14px 16px;
  font-size: 16px;
  font-family: var(--sans);
  margin-bottom: 22px;
}

.search:focus {
  outline: 1px solid var(--copper);
}

.filters {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 22px;
}

.chip {
  border: 1px solid var(--line);
  background: transparent;
  color: var(--muted);
  padding: 6px 12px;
  font-size: 13px;
  cursor: pointer;
  font-family: var(--sans);
  display: inline-flex;
  align-items: center;
  text-decoration: none;
}

.chip.on, .chip:hover {
  border-color: var(--copper);
  color: var(--ink);
}

.footer {
  border-top: 1px solid var(--line);
  padding: 36px 0 48px;
  color: var(--dim);
  font-size: 13px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 24px;
}

.footer a { color: var(--muted); }
.footer .brand strong { font-size: 16px; }

.path-list {
  display: grid;
  gap: 14px;
}

.path-item {
  display: grid;
  grid-template-columns: 88px 1fr;
  gap: 16px;
  border: 1px solid var(--line);
  background: var(--bg-card);
  padding: 18px;
}

.path-item .n {
  font-family: var(--mono);
  color: var(--copper);
  font-size: 22px;
}

.hidden { display: none !important; }

.schematic {
  border: 1px solid var(--line);
  background: rgba(17, 21, 27, 0.85);
  padding: 18px 12px 8px;
  margin: 16px 0 22px;
  overflow-x: auto;
}
.schematic svg {
  display: block;
  margin: 0 auto;
  max-width: 100%;
  height: auto;
}
.schematic figcaption {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--dim);
  letter-spacing: 0.12em;
  text-align: center;
  padding: 8px 0 4px;
}

.part-block {
  scroll-margin-top: 96px;
  border-top: 1px solid var(--line);
  padding-top: 36px;
  margin-top: 8px;
}

.duo {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

.split-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

.poster-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 28px;
}
.poster {
  scroll-margin-top: 96px;
  border: 1px solid var(--line);
  background: #f4f7fb;
  overflow: hidden;
}
.poster button {
  display: block;
  width: 100%;
  padding: 0;
  border: 0;
  background: transparent;
  cursor: zoom-in;
}
.poster img {
  width: 100%;
  height: auto;
  display: block;
  vertical-align: top;
}
.poster-cap {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  align-items: baseline;
  padding: 12px 16px;
  background: var(--bg-card);
  border-top: 1px solid var(--line);
}
.poster-cap .ref {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--solder);
  letter-spacing: 0.14em;
}
.poster-cap h3 {
  margin: 0;
  font-size: 18px;
}

.lightbox {
  position: fixed;
  inset: 0;
  z-index: 80;
  display: none;
  place-items: center;
  background: rgba(6, 8, 10, 0.92);
  padding: 24px;
}
.lightbox.open { display: grid; }
.lightbox img {
  max-width: min(1200px, 100%);
  max-height: calc(100vh - 80px);
  width: auto;
  height: auto;
  box-shadow: var(--shadow);
}
.lightbox .lb-bar {
  position: absolute;
  top: 16px;
  right: 16px;
  display: flex;
  gap: 8px;
}
.lightbox button {
  min-width: 44px;
  min-height: 40px;
  border: 1px solid var(--line-strong);
  background: var(--bg-card);
  color: var(--ink);
  font-family: var(--mono);
  cursor: pointer;
}

@media (max-width: 1200px) {
  .cards { grid-template-columns: 1fr 1fr; }
  .hero-grid, .article, .footer-grid, .flow, .duo, .split-2 { grid-template-columns: 1fr; }
  .toc { position: static; }
  .menu-btn { display: block; }
  .nav-links {
    display: none;
    position: absolute;
    top: 72px;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: flex-start;
    padding: 16px 20px 22px;
    background: rgba(10, 12, 15, 0.96);
    border-bottom: 1px solid var(--line);
  }
  .nav-links.open { display: flex; }
}

@media (max-width: 640px) {
  .cards { grid-template-columns: 1fr; }
  .path-item { grid-template-columns: 1fr; }
}