/* ============================================================
   Self-FDE WorkBench — "Engineer's Blueprint Notebook"
   Dark ink · graph paper · signal orange · draughtsman's mono
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Instrument+Serif:ital@0;1&family=IBM+Plex+Mono:wght@300;400;500;600&display=swap');

:root {
  --ink:        #0A0B0D;
  --ink-2:      #101317;
  --ink-3:      #171B21;
  --line:       rgba(232, 228, 220, 0.10);
  --line-soft:  rgba(232, 228, 220, 0.05);
  --paper:      #E8E4DC;
  --paper-dim:  #A5A69F;
  --muted:      #6E7278;
  --signal:     #FF6B35;
  --signal-dim: rgba(255, 107, 53, 0.14);
  --teal:       #7FDBCA;
  --teal-dim:   rgba(127, 219, 202, 0.12);

  --mono: 'IBM Plex Mono', ui-monospace, 'SF Mono', Menlo, monospace;
  --serif: 'Instrument Serif', 'Songti SC', Georgia, serif;
  --han: 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  --body: var(--mono), var(--han);

  --max: 1180px;
}

*, *::before, *::after { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--ink);
  color: var(--paper);
  font-family: var(--mono), var(--han);
  font-weight: 300;
  font-size: 15px;
  line-height: 1.85;
  letter-spacing: 0.01em;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

/* ---------- graph-paper substrate ---------- */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    linear-gradient(var(--line-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--line-soft) 1px, transparent 1px);
  background-size: 28px 28px;
  mask-image: radial-gradient(ellipse 130% 90% at 50% 0%, #000 20%, transparent 90%);
}
/* film grain */
body::after {
  content: '';
  position: fixed;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  opacity: 0.22;
  mix-blend-mode: overlay;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='140' height='140'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='3'/%3E%3C/filter%3E%3Crect width='140' height='140' filter='url(%23n)' opacity='0.5'/%3E%3C/svg%3E");
}

main, header, footer, nav { position: relative; z-index: 2; }

.wrap { width: 100%; max-width: var(--max); margin: 0 auto; padding: 0 28px; }

/* ---------- type ---------- */
h1, h2, h3 { font-weight: 400; letter-spacing: -0.01em; line-height: 1.25; margin: 0; }

.serif { font-family: var(--serif), var(--han); font-weight: 400; }

.eyebrow {
  font-size: 11px;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--signal);
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 12px;
}
.eyebrow::after {
  content: '';
  flex: 1;
  height: 1px;
  background: linear-gradient(90deg, var(--signal-dim), transparent);
}

a { color: var(--paper); text-decoration: none; }

p { margin: 0 0 1.1em; color: var(--paper-dim); }
strong { color: var(--paper); font-weight: 500; }
em { font-family: var(--serif), var(--han); font-style: italic; color: var(--paper); }

code {
  font-family: var(--mono);
  font-size: 0.88em;
  color: var(--teal);
  background: var(--teal-dim);
  padding: 1px 6px;
  border-radius: 3px;
}

/* ---------- nav ---------- */
nav.top {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(14px);
  background: rgba(10, 11, 13, 0.72);
  border-bottom: 1px solid var(--line);
}
nav.top .wrap {
  display: flex;
  align-items: center;
  gap: 28px;
  height: 62px;
}
.brand {
  font-family: var(--mono);
  font-weight: 600;
  font-size: 13px;
  letter-spacing: 0.06em;
  display: flex;
  align-items: center;
  gap: 9px;
  margin-right: auto;
  white-space: nowrap;
}
.brand .dot {
  width: 7px; height: 7px;
  background: var(--signal);
  border-radius: 50%;
  box-shadow: 0 0 12px var(--signal);
  animation: pulse 2.6s ease-in-out infinite;
}
@keyframes pulse { 0%,100% { opacity: 1; } 50% { opacity: 0.35; } }

nav.top a.link {
  font-size: 12.5px;
  color: var(--muted);
  letter-spacing: 0.04em;
  transition: color .2s;
  position: relative;
  white-space: nowrap;
}
nav.top a.link:hover, nav.top a.link[aria-current] { color: var(--paper); }
nav.top a.link[aria-current]::after {
  content: '';
  position: absolute;
  left: 0; right: 0; bottom: -21px;
  height: 1px;
  background: var(--signal);
}
.nav-scroll { display: flex; gap: 26px; overflow-x: auto; scrollbar-width: none; }
.nav-scroll::-webkit-scrollbar { display: none; }

/* ---------- language toggle ---------- */
.lang {
  display: flex;
  align-items: stretch;
  border: 1px solid var(--line);
  margin-left: 22px;
  flex-shrink: 0;
}
.lang-btn {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  padding: 6px 11px;
  background: transparent;
  border: 0;
  color: var(--muted);
  cursor: pointer;
  transition: color .18s, background .18s;
  line-height: 1.5;
}
.lang-btn + .lang-btn { border-left: 1px solid var(--line); }
.lang-btn:hover { color: var(--paper); }
.lang-btn[aria-pressed="true"] {
  background: var(--signal);
  color: var(--ink);
  font-weight: 600;
}

/* Chinese needs a different serif stack and slightly tighter display sizes —
   Instrument Serif has no CJK glyphs, so headings would silently fall back. */
:root[data-lang="zh"] {
  --serif: 'Instrument Serif', 'Songti SC', 'Source Han Serif SC', Georgia, serif;
}
/* `ch` is sized off the Latin "0" glyph, so a ch-based max-width clips CJK
   headlines mid-word. Size the Chinese headline in `em` instead. */
:root[data-lang="zh"] .hero h1 { max-width: 10em; }

/* English says the same thing in ~1.5x the characters, which pushed the hero's
   CTA below the fold. The <br> already sets the line break, so max-width only has
   to be wide enough not to wrap a third time — and the type drops one step to buy
   back the height. Chinese is untouched: it already fit. */
:root[data-lang="en"] .hero h1 {
  max-width: none;
  font-size: clamp(34px, 4.4vw, 58px);
}

/* ---------- hero ---------- */
.hero { padding: 68px 0 80px; position: relative; }
.hero .kicker {
  font-size: 12px;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 24px;
}
.hero .kicker b { color: var(--signal); font-weight: 500; }

.hero h1 {
  font-family: var(--serif), var(--han);
  font-size: clamp(40px, 6.6vw, 82px);
  line-height: 1.08;
  letter-spacing: -0.02em;
  margin-bottom: 28px;
  max-width: 15ch;
}
.hero h1 .strike {
  color: var(--muted);
  text-decoration: line-through;
  text-decoration-color: var(--signal);
  text-decoration-thickness: 3px;
}
.hero h1 .glow { color: var(--signal); font-style: italic; }

.hero .lede {
  font-size: 16px;
  max-width: 58ch;
  color: var(--paper-dim);
  line-height: 1.85;
}
.hero .lede b { color: var(--paper); font-weight: 500; }

.hero-actions { display: flex; gap: 14px; margin-top: 24px; flex-wrap: wrap; }

.btn {
  font-family: var(--mono);
  font-size: 12.5px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 13px 22px;
  border: 1px solid var(--line);
  color: var(--paper);
  transition: all .22s ease;
  display: inline-flex;
  align-items: center;
  gap: 9px;
  background: transparent;
}
.btn:hover { border-color: var(--signal); color: var(--signal); transform: translateY(-1px); }
.btn.primary {
  background: var(--signal);
  border-color: var(--signal);
  color: var(--ink);
  font-weight: 600;
}
.btn.primary:hover { background: transparent; color: var(--signal); }

/* ---------- sections ---------- */
section { padding: 96px 0; border-top: 1px solid var(--line); }
.sec-head { margin-bottom: 56px; max-width: 62ch; }
.sec-head h2 {
  font-family: var(--serif), var(--han);
  font-size: clamp(28px, 3.6vw, 42px);
  margin: 22px 0 20px;
  letter-spacing: -0.01em;
}
.sec-head p { font-size: 15px; }

/* ---------- diagram frame ---------- */
.diagram-frame {
  border: 1px solid var(--line);
  background:
    linear-gradient(var(--line-soft) 1px, transparent 1px) 0 0 / 24px 24px,
    linear-gradient(90deg, var(--line-soft) 1px, transparent 1px) 0 0 / 24px 24px,
    var(--ink-2);
  padding: 8px;
  position: relative;
  overflow-x: auto;
}
.diagram-frame::before,
.diagram-frame::after {
  content: '';
  position: absolute;
  width: 9px; height: 9px;
  border: 1px solid var(--signal);
}
.diagram-frame::before { top: -1px; left: -1px; border-right: 0; border-bottom: 0; }
.diagram-frame::after  { bottom: -1px; right: -1px; border-left: 0; border-top: 0; }

.diagram-frame svg { display: block; min-width: 900px; width: 100%; height: auto; }

.diagram-cap {
  display: flex;
  justify-content: space-between;
  gap: 20px;
  margin-top: 14px;
  font-size: 11px;
  color: var(--muted);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  flex-wrap: wrap;
}

/* SVG diagram tokens */
.d-box { fill: var(--ink-3); stroke: var(--line); stroke-width: 1; }
.d-box-hot { fill: rgba(255,107,53,0.06); stroke: rgba(255,107,53,0.45); }
.d-box-cool { fill: rgba(127,219,202,0.05); stroke: rgba(127,219,202,0.32); }
.d-t   { font-family: var(--mono), var(--han); font-size: 13px; fill: var(--paper); font-weight: 400; }
.d-t-s { font-family: var(--mono), var(--han); font-size: 10.5px; fill: var(--muted); }
.d-t-hot  { fill: var(--signal); }
.d-t-cool { fill: var(--teal); }
.d-label {
  font-family: var(--mono);
  font-size: 9.5px;
  letter-spacing: 0.22em;
  fill: var(--muted);
  text-transform: uppercase;
}
.d-arrow { stroke: rgba(232,228,220,0.30); stroke-width: 1.2; fill: none; }
.d-arrow-hot { stroke: var(--signal); stroke-width: 1.4; fill: none; }
.d-arrow-dash { stroke-dasharray: 4 4; }
.d-zone { fill: none; stroke: var(--line); stroke-width: 1; stroke-dasharray: 2 5; }

/* draw-in animation */
.draw { stroke-dasharray: 900; stroke-dashoffset: 900; animation: draw 2s ease forwards; }
@keyframes draw { to { stroke-dashoffset: 0; } }

/* ---------- cards ---------- */
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }

.card {
  border: 1px solid var(--line);
  background: var(--ink-2);
  padding: 30px 28px 32px;
  position: relative;
  transition: border-color .25s, transform .25s, background .25s;
  display: block;
  overflow: hidden;
}
.card::after {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(circle at 100% 0%, var(--signal-dim), transparent 55%);
  opacity: 0;
  transition: opacity .3s;
  pointer-events: none;
}
.card:hover { border-color: rgba(255,107,53,0.4); transform: translateY(-3px); }
.card:hover::after { opacity: 1; }

.card .idx {
  font-size: 10.5px;
  letter-spacing: 0.2em;
  color: var(--signal);
  font-weight: 500;
  margin-bottom: 18px;
  display: block;
}
.card h3 {
  font-family: var(--serif), var(--han);
  font-size: 26px;
  margin-bottom: 6px;
}
.card .sub {
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 18px;
}
.card p { font-size: 13.5px; line-height: 1.8; margin-bottom: 0; }
.card .go {
  margin-top: 22px;
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  display: flex;
  align-items: center;
  gap: 8px;
  transition: color .2s, gap .2s;
}
.card:hover .go { color: var(--signal); gap: 14px; }

/* pull-quote */
.quote {
  border-left: 2px solid var(--signal);
  padding: 6px 0 6px 28px;
  margin: 44px 0;
  max-width: 66ch;
}
.quote p {
  font-family: var(--serif), var(--han);
  font-size: clamp(21px, 2.5vw, 28px);
  line-height: 1.6;
  color: var(--paper);
  margin: 0;
}
.quote cite {
  display: block;
  margin-top: 14px;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  font-style: normal;
}

/* spec table */
.spec { width: 100%; border-collapse: collapse; font-size: 13.5px; }
.spec th, .spec td {
  text-align: left;
  padding: 15px 18px;
  border: 1px solid var(--line);
  vertical-align: top;
}
.spec th {
  font-size: 10.5px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 500;
  background: var(--ink-2);
}
.spec td { color: var(--paper-dim); }
.spec td:first-child { color: var(--paper); white-space: nowrap; }
.spec tr:hover td { background: var(--ink-2); }

/* status chip */
.chip {
  display: inline-block;
  font-size: 10px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  padding: 3px 9px;
  border: 1px solid var(--line);
  color: var(--muted);
  border-radius: 2px;
}
.chip.live   { color: var(--teal);   border-color: rgba(127,219,202,0.4); }
.chip.wip    { color: var(--signal); border-color: rgba(255,107,53,0.4); }

/* sketch */
figure.sketch { margin: 0; }
figure.sketch img {
  width: 100%;
  border: 1px solid var(--line);
  filter: grayscale(1) contrast(1.16) brightness(0.82) invert(1) hue-rotate(180deg);
  opacity: 0.72;
  transition: opacity .4s, filter .4s;
}
figure.sketch img:hover { opacity: 1; filter: none; }
figure.sketch figcaption {
  margin-top: 12px;
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
}

/* prose (subpages) */
.prose { max-width: 68ch; }
.prose h2 {
  font-family: var(--serif), var(--han);
  font-size: 30px;
  margin: 60px 0 20px;
  padding-top: 26px;
  border-top: 1px solid var(--line);
}
.prose h3 {
  font-size: 15px;
  letter-spacing: 0.02em;
  color: var(--paper);
  margin: 36px 0 12px;
  font-weight: 500;
}
.prose h3::before { content: '// '; color: var(--signal); }
.prose ul { padding-left: 0; list-style: none; margin: 0 0 1.4em; }
.prose li {
  color: var(--paper-dim);
  font-size: 14px;
  padding: 7px 0 7px 24px;
  position: relative;
  line-height: 1.8;
}
.prose li::before {
  content: '─';
  position: absolute;
  left: 0;
  color: var(--signal);
  opacity: 0.55;
}

/* footer */
footer {
  border-top: 1px solid var(--line);
  padding: 54px 0 70px;
  font-size: 12px;
  color: var(--muted);
}
footer .wrap { display: flex; justify-content: space-between; gap: 26px; flex-wrap: wrap; align-items: flex-end; }
footer a { color: var(--paper-dim); }
footer a:hover { color: var(--signal); }
footer .links { display: flex; gap: 22px; flex-wrap: wrap; }

/* reveal on load / scroll */
.rise { opacity: 0; transform: translateY(18px); animation: rise .8s cubic-bezier(.2,.7,.3,1) forwards; }
@keyframes rise { to { opacity: 1; transform: none; } }
.d1 { animation-delay: .08s; } .d2 { animation-delay: .18s; }
.d3 { animation-delay: .28s; } .d4 { animation-delay: .40s; }
.d5 { animation-delay: .52s; }

.io { opacity: 0; transform: translateY(22px); transition: opacity .9s cubic-bezier(.2,.7,.3,1), transform .9s cubic-bezier(.2,.7,.3,1); }
.io.in { opacity: 1; transform: none; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
  .io { opacity: 1; transform: none; }
  .draw { stroke-dashoffset: 0; }
}

@media (max-width: 860px) {
  .grid-3, .grid-2 { grid-template-columns: 1fr; }
  .hero { padding: 76px 0 60px; }
  section { padding: 68px 0; }
  .wrap { padding: 0 20px; }
  nav.top a.link[aria-current]::after { display: none; }
}