/* ============ GatherThread — Apple-grade product page · Liquid Glass ============ */

:root {
  --brand-cyan: #20C1DC;
  --brand-blue: #2E96F5;
  --brand-violet: #A766F0;
  --brand-pink: #F66DB9;
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text", "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
  --ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-in-out-quart: cubic-bezier(0.77, 0, 0.18, 1);
}

html[data-theme="dark"] {
  color-scheme: dark;
  --bg: #000000;
  --bg-1: #111114;
  --bg-2: #1c1c21;
  --band-alt: rgba(255, 255, 255, 0.035);
  --text: #f5f5f7;
  --text-2: rgba(245, 245, 247, 0.68);
  --text-3: rgba(245, 245, 247, 0.44);
  --hairline: rgba(255, 255, 255, 0.14);
  --nav-bg: rgba(12, 12, 14, 0.45);
  /* Liquid glass */
  --glass-bg: rgba(255, 255, 255, 0.05);
  --glass-bg-strong: rgba(17, 17, 20, 0.55);
  --glass-edge: rgba(255, 255, 255, 0.16);
  --glass-spec: rgba(255, 255, 255, 0.3);
  --glass-spec-strong: rgba(255, 255, 255, 0.5);
  --glass-shade: rgba(0, 0, 0, 0.35);
  --glass-sheen: rgba(255, 255, 255, 0.12);
  --glass-shadow: rgba(0, 0, 0, 0.4);
}

html[data-theme="light"] {
  color-scheme: light;
  --bg: #ffffff;
  --bg-1: #f5f5f7;
  --bg-2: #e8e8ed;
  --band-alt: rgba(0, 0, 0, 0.025);
  --text: #1d1d1f;
  --text-2: rgba(29, 29, 31, 0.68);
  --text-3: rgba(29, 29, 31, 0.44);
  --hairline: rgba(0, 0, 0, 0.12);
  --nav-bg: rgba(255, 255, 255, 0.45);
  /* Liquid glass */
  --glass-bg: rgba(245, 245, 247, 0.6);
  --glass-bg-strong: rgba(250, 250, 252, 0.6);
  --glass-edge: rgba(0, 0, 0, 0.08);
  --glass-spec: rgba(255, 255, 255, 0.95);
  --glass-spec-strong: rgba(255, 255, 255, 1);
  --glass-shade: rgba(0, 0, 0, 0.08);
  --glass-sheen: rgba(255, 255, 255, 0.85);
  --glass-shadow: rgba(0, 0, 0, 0.16);
}

* { margin: 0; padding: 0; box-sizing: border-box; }

.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;
}

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
  transition: background-color 0.3s ease, color 0.3s ease;
}

.mono {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.08em;
}

.wrap { max-width: 1080px; margin: 0 auto; padding: 0 24px; }

/* Shared liquid-glass material: deep blur + specular top edge + refractive rim */
.glass,
.card,
.col,
.rows,
.spec,
.statement .wrap {
  background: var(--glass-bg);
  -webkit-backdrop-filter: blur(40px) saturate(200%);
  backdrop-filter: blur(40px) saturate(200%);
  box-shadow:
    inset 0 1.5px 0 0 var(--glass-spec),
    inset 0 -1.5px 0 0 var(--glass-shade),
    inset 0 0 0 1px var(--glass-edge),
    0 28px 56px -22px var(--glass-shadow);
}

/* Directional refractive rim — light enters top-left, exits bottom-right */
.card::after,
.col::after,
.rows::after,
.spec::after,
.statement .wrap::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  padding: 1.5px;
  pointer-events: none;
  background: linear-gradient(155deg, var(--glass-spec-strong), transparent 32%, transparent 68%, var(--glass-shade));
  -webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  -webkit-mask-composite: xor;
  mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
  mask-composite: exclude;
}

/* ============ NAV ============ */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  background: var(--nav-bg);
  -webkit-backdrop-filter: blur(32px) saturate(200%);
  backdrop-filter: blur(32px) saturate(200%);
  box-shadow: inset 0 -1px 0 0 transparent;
  transition: background-color 0.3s ease, box-shadow 0.5s ease;
}
.nav.scrolled {
  box-shadow:
    inset 0 -1px 0 0 var(--glass-edge),
    inset 0 -2px 0 -1px var(--glass-shade),
    0 12px 32px -16px var(--glass-shadow);
}

.nav-inner {
  max-width: 1080px;
  margin: 0 auto;
  padding: 0 24px;
  height: 52px;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
}

.nav-brand { display: inline-flex; align-items: center; justify-self: start; }
.brand-lockup { height: 20px; width: auto; display: block; }
html[data-theme="dark"] .lockup-for-light { display: none; }
html[data-theme="light"] .lockup-for-dark { display: none; }

.nav-links { display: flex; gap: 36px; justify-self: center; }
.nav-links a {
  color: var(--text-2);
  text-decoration: none;
  font-size: 12px;
  letter-spacing: 0.01em;
  transition: color 0.15s ease;
}
.nav-links a:hover { color: var(--text); }

a:focus-visible,
button:focus-visible {
  outline: 3px solid var(--brand-cyan);
  outline-offset: 4px;
}

.nav-actions { display: flex; align-items: center; gap: 16px; justify-self: end; }

.theme-toggle {
  position: relative;
  width: 34px; height: 34px;
  border: none;
  border-radius: 50%;
  background: var(--glass-bg);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  backdrop-filter: blur(20px) saturate(180%);
  box-shadow:
    inset 0 1px 0 0 var(--glass-spec),
    inset 0 -1px 0 0 var(--glass-shade),
    inset 0 0 0 1px var(--glass-edge);
  color: var(--text-2);
  cursor: pointer;
  display: grid;
  place-items: center;
  transition: color 0.15s ease, box-shadow 0.2s ease, transform 0.15s ease;
}
.theme-toggle:hover { color: var(--text); }
.theme-toggle:active { transform: scale(0.92); }
.theme-toggle svg {
  position: absolute;
  width: 18px; height: 18px;
  transition: opacity 0.3s ease, transform 0.45s var(--ease-out-expo);
}
html[data-theme="dark"] .icon-sun { opacity: 0; transform: rotate(-90deg) scale(0.5); }
html[data-theme="dark"] .icon-moon { opacity: 1; transform: rotate(0) scale(1); }
html[data-theme="light"] .icon-sun { opacity: 1; transform: rotate(0) scale(1); }
html[data-theme="light"] .icon-moon { opacity: 0; transform: rotate(90deg) scale(0.5); }

.nav-cta {
  font-size: 12px;
  color: #fff;
  background: linear-gradient(180deg, #55adf7 0%, var(--brand-blue) 100%);
  padding: 6px 14px;
  border-radius: 999px;
  text-decoration: none;
  box-shadow:
    inset 0 1px 0 0 rgba(255, 255, 255, 0.4),
    inset 0 -1px 0 0 rgba(0, 0, 0, 0.15),
    0 6px 16px -6px rgba(46, 150, 245, 0.55);
  transition: filter 0.15s ease, transform 0.15s ease;
}
.nav-cta:hover { filter: brightness(1.08); }
.nav-cta:active { transform: scale(0.96); }

/* ============ HERO ============ */
.hero {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 140px 24px 80px;
}

.hero-eyebrow {
  color: var(--text-3);
  margin-bottom: 28px;
  opacity: 0;
  animation: fade-in 0.8s ease 0.1s forwards;
}

.hero-title {
  font-size: clamp(52px, 10.5vw, 120px);
  font-weight: 700;
  line-height: 1.04;
  letter-spacing: -0.025em;
  color: var(--text);
}
.hero-title .line { display: block; overflow: hidden; padding-bottom: 0.08em; margin-bottom: -0.08em; }
.hero-title .char {
  display: inline-block;
  transform: translateY(115%);
  will-change: transform;
}
.hero-title.in .char {
  transform: translateY(0);
  transition: transform 1s var(--ease-in-out-quart);
  transition-delay: var(--d, 0s);
}
.hero-tagline {
  margin-top: 30px;
  font-size: clamp(17px, 2vw, 21px);
  color: var(--text-2);
  letter-spacing: 0.02em;
  opacity: 0;
  animation: fade-in 0.8s ease 0.9s forwards;
}

.hero-copy {
  margin-top: 14px;
  font-size: clamp(15px, 1.6vw, 17px);
  line-height: 1.7;
  color: var(--text-3);
  opacity: 0;
  animation: fade-in 0.8s ease 1.05s forwards;
}

.hero-ctas {
  margin-top: 36px;
  display: flex;
  align-items: center;
  gap: 28px;
  opacity: 0;
  animation: fade-in 0.8s ease 1.2s forwards;
}

.btn-pill {
  display: inline-block;
  background: linear-gradient(180deg, #55adf7 0%, var(--brand-blue) 100%);
  color: #fff;
  font-size: 17px;
  padding: 12px 26px;
  border-radius: 999px;
  text-decoration: none;
  box-shadow:
    inset 0 1px 0 0 rgba(255, 255, 255, 0.4),
    inset 0 -1px 0 0 rgba(0, 0, 0, 0.15),
    0 10px 24px -8px rgba(46, 150, 245, 0.55);
  transition: filter 0.15s ease, transform 0.15s ease, box-shadow 0.2s ease;
}
.btn-pill:hover {
  filter: brightness(1.08);
  box-shadow:
    inset 0 1px 0 0 rgba(255, 255, 255, 0.5),
    inset 0 -1px 0 0 rgba(0, 0, 0, 0.15),
    0 14px 32px -8px rgba(46, 150, 245, 0.65);
}
.btn-pill:active { transform: scale(0.97); }

.btn-link {
  color: var(--brand-blue);
  font-size: 17px;
  text-decoration: none;
  transition: opacity 0.15s ease;
}
.btn-link:hover { text-decoration: underline; }
.btn-link .chev { margin-left: 4px; font-weight: 600; }

.hero-mark {
  margin-top: 72px;
  width: min(560px, 78vw);
  opacity: 0;
  animation: fade-in 0.6s ease 1.35s forwards;
}
.hero-mark svg { width: 100%; height: auto; display: block; }

.thread {
  stroke-dasharray: 1000;
  stroke-dashoffset: 1000;
}
.hero-mark.drawn .thread {
  stroke-dashoffset: 0;
  transition: stroke-dashoffset 1.5s var(--ease-in-out-quart);
}
.hero-mark.drawn .thread:nth-child(1) { transition-delay: 0.15s; }
.hero-mark.drawn .thread:nth-child(2) { transition-delay: 0.0s; }
.hero-mark.drawn .thread:nth-child(3) { transition-delay: 0.3s; }
.hero-mark.drawn .thread:nth-child(4) { transition-delay: 0.45s; }

.thread-dots circle {
  transform-origin: center;
  transform-box: fill-box;
  transform: scale(0);
}
.hero-mark.drawn .thread-dots circle {
  transform: scale(1);
  transition: transform 0.5s var(--ease-out-expo);
}
.hero-mark.drawn .thread-dots circle:nth-child(1) { transition-delay: 0.55s; }
.hero-mark.drawn .thread-dots circle:nth-child(2) { transition-delay: 0.65s; }
.hero-mark.drawn .thread-dots circle:nth-child(3) { transition-delay: 0.75s; }
.hero-mark.drawn .thread-dots circle:nth-child(4) { transition-delay: 0.85s; }

@keyframes fade-in { to { opacity: 1; } }

/* ============ BANDS ============ */
.band { padding: 130px 0; transition: background-color 0.3s ease; }
.band-alt { background: var(--band-alt); }

.label { color: var(--text-3); margin-bottom: 20px; }

.h2 {
  font-size: clamp(36px, 5.5vw, 64px);
  font-weight: 700;
  line-height: 1.1;
  letter-spacing: -0.02em;
  margin-bottom: 24px;
}

.lead {
  font-size: clamp(16px, 1.8vw, 19px);
  line-height: 1.7;
  color: var(--text-2);
  max-width: 640px;
}

/* Statement: whole block inside a glass panel */
.statement { text-align: left; }
.statement .wrap {
  position: relative;
  border-radius: 32px;
  padding: 72px 64px;
}
.statement .h2 { max-width: 800px; }
.statement .lead { margin-top: 8px; }

/* ============ DUO CARDS ============ */
.duo {
  margin-top: 56px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 24px;
}

.card {
  position: relative;
  overflow: hidden;
  border-radius: 28px;
  padding: 48px 44px;
  transition: box-shadow 0.3s ease, background-color 0.3s ease;
}
/* Pointer-tracked specular sheen */
.card::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  pointer-events: none;
  background: radial-gradient(340px circle at var(--mx, 50%) var(--my, -30%), var(--glass-sheen), transparent 65%);
  opacity: 0;
  transition: opacity 0.25s ease;
}
.card:hover::before { opacity: 1; }

.card-tag { color: var(--text-3); margin-bottom: 22px; }

.card h3 {
  font-size: 28px;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 14px;
}
.card p { font-size: 15px; line-height: 1.7; color: var(--text-2); }

.card-solo { border-top: 3px solid var(--brand-cyan); }
.card-multi { border-top: 3px solid var(--brand-pink); }

/* ============ FIDELITY ROWS — one glass panel ============ */
.rows {
  position: relative;
  margin-top: 56px;
  border-radius: 28px;
  padding: 16px 44px;
}
.row {
  display: grid;
  grid-template-columns: 280px 1fr;
  gap: 32px;
  padding: 36px 0;
  border-bottom: 1px solid var(--hairline);
  transition: border-color 0.3s ease;
}
.rows .row:last-child { border-bottom: none; }
.row-tag { color: var(--text-3); padding-top: 6px; }
.row h3 { font-size: 21px; font-weight: 600; margin-bottom: 8px; }
.row p:not(.row-tag) { font-size: 15px; line-height: 1.7; color: var(--text-2); }

/* ============ THREAD DIVIDER ============ */
.thread-divider {
  padding: 90px 0;
  text-align: center;
}
.thread-divider svg { width: 100%; height: 60px; display: block; }
#dividerPath {
  stroke-dasharray: 1000;
  stroke-dashoffset: calc(1000 - (1000 * var(--p, 0)));
}
.divider-caption {
  margin-top: 28px;
  color: var(--text-3);
  letter-spacing: 0.3em;
}

/* ============ TRIO COLUMNS ============ */
.trio {
  margin-top: 56px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
.col {
  position: relative;
  overflow: hidden;
  padding: 40px 32px;
  border-radius: 28px;
  transition: box-shadow 0.3s ease, background-color 0.3s ease;
}
.col::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  pointer-events: none;
  background: radial-gradient(300px circle at var(--mx, 50%) var(--my, -30%), var(--glass-sheen), transparent 65%);
  opacity: 0;
  transition: opacity 0.25s ease;
}
.col:hover::before { opacity: 1; }
.col h3 { font-size: 21px; font-weight: 600; margin-bottom: 12px; }
.col p { font-size: 14px; line-height: 1.7; color: var(--text-2); margin-bottom: 24px; min-height: 72px; }
.col code {
  display: block;
  font-size: 12px;
  color: var(--text);
  background: var(--glass-bg);
  box-shadow:
    inset 0 1px 0 0 var(--glass-spec),
    inset 0 0 0 1px var(--glass-edge);
  padding: 12px 16px;
  border-radius: 12px;
  overflow-x: auto;
  white-space: nowrap;
  transition: background-color 0.3s ease;
}

/* ============ STEPS ============ */
.steps { list-style: none; counter-reset: step; }
.steps li {
  counter-increment: step;
  position: relative;
  padding: 14px 0 14px 52px;
  font-size: 15px;
  line-height: 1.6;
  color: var(--text-2);
  border-bottom: 1px solid var(--hairline);
}
.steps li:last-child { border-bottom: none; }
.steps li::before {
  content: counter(step);
  position: absolute;
  left: 0; top: 14px;
  width: 30px; height: 30px;
  border-radius: 50%;
  background: var(--glass-bg);
  box-shadow:
    inset 0 1px 0 0 var(--glass-spec),
    inset 0 0 0 1px var(--glass-edge);
  color: var(--text);
  font-size: 13px;
  font-weight: 600;
  display: grid;
  place-items: center;
  transition: background-color 0.3s ease;
}

/* ============ SECURITY — theme-consistent glass panel ============ */
.sec-grid {
  margin-top: 56px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--hairline);
  border-radius: 28px;
  overflow: hidden;
  box-shadow:
    inset 0 0 0 1px var(--glass-edge),
    0 28px 56px -22px var(--glass-shadow);
  transition: box-shadow 0.3s ease, background-color 0.3s ease;
}
.sec-item {
  background: var(--glass-bg-strong);
  -webkit-backdrop-filter: blur(40px) saturate(200%);
  backdrop-filter: blur(40px) saturate(200%);
  padding: 32px 26px;
  transition: background-color 0.3s ease;
}
.sec-item h3 { font-size: 16px; font-weight: 600; margin-bottom: 8px; color: var(--text); }
.sec-item p { font-size: 13px; line-height: 1.6; color: var(--text-2); }

/* ============ SPECS — glass tiles ============ */
.spec-strip {
  margin-top: 24px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  text-align: center;
}
.spec {
  position: relative;
  border-radius: 24px;
  padding: 44px 16px 36px;
}
.spec-num {
  font-size: clamp(40px, 5vw, 56px);
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
}
.spec-key { margin-top: 8px; font-size: 13px; color: var(--text-3); }

/* ============ FINAL CTA ============ */
.final-cta { text-align: center; }
.final-cta .hero-ctas { justify-content: center; }

/* ============ FOOTER ============ */
.footer {
  border-top: 1px solid var(--hairline);
  padding: 48px 0 56px;
  transition: border-color 0.3s ease;
}
.footnotes p {
  font-size: 12px;
  line-height: 1.7;
  color: var(--text-3);
  margin-bottom: 8px;
}
.footer-bar {
  margin-top: 36px;
  padding-top: 24px;
  border-top: 1px solid var(--hairline);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  flex-wrap: wrap;
  transition: border-color 0.3s ease;
}
.footer-lockup { height: 18px; width: auto; }
.copyright { font-size: 12px; color: var(--text-3); }
.footer-contact {
  margin-top: 24px;
  color: var(--text-2);
  font-size: 13px;
  line-height: 1.7;
  text-align: center;
}
.footer-contact a {
  color: inherit;
  text-decoration: underline;
  text-underline-offset: 3px;
}
.footer-contact a:hover { color: var(--text); }

/* ============ RESPONSIVE ============ */
@media (max-width: 900px) {
  .nav-links { display: none; }
  .nav-inner { grid-template-columns: 1fr auto; }
  .nav-actions { grid-column: 2; }
  .duo, .trio { grid-template-columns: 1fr; }
  .sec-grid { grid-template-columns: 1fr 1fr; }
  .spec-strip { grid-template-columns: 1fr 1fr; row-gap: 24px; }
  .row { grid-template-columns: 1fr; gap: 12px; }
  .rows { padding: 8px 24px; }
  .statement .wrap { padding: 48px 28px; }
  .col p { min-height: 0; }
  .band { padding: 90px 0; }
  .br-wide { display: none; }
}

@media (max-width: 380px) {
  .nav-inner {
    padding: 0 12px;
    column-gap: 8px;
  }
  .brand-lockup { height: 17px; }
  .nav-actions { gap: 8px; }
  .lang-toggle {
    min-width: 36px;
    height: 32px;
    padding: 0 8px;
  }
  .theme-toggle {
    width: 32px;
    height: 32px;
  }
  .nav-cta {
    padding: 6px 10px;
    white-space: nowrap;
  }
}

/* ============ REDUCED MOTION ============ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-delay: 0s !important;
    transition-duration: 0.01ms !important;
    transition-delay: 0s !important;
  }
  .hero-eyebrow,
  .hero-tagline,
  .hero-copy,
  .hero-ctas,
  .hero-mark,
  .page .fx {
    opacity: 1 !important;
    transform: none !important;
  }
  .hero-title .char { transform: none; }
  .thread { stroke-dashoffset: 0; }
  .thread-dots circle { transform: scale(1); }
  #dividerPath { stroke-dashoffset: 0; }
}

/* ============ FIXED ANIMATED COLOR FIELD ============ */
/* Viewport-pinned. Motion is driven by requestAnimationFrame in app.js so it
   runs in every embedded browser; CSS only defines the static material. */
html[data-theme="dark"] { --orb-op: 0.55; --ring-op: 0.55; }
html[data-theme="light"] { --orb-op: 0.35; --ring-op: 0.4; }

.bg-field {
  position: fixed;
  inset: 0;
  z-index: -1;
  overflow: hidden;
  pointer-events: none;
  will-change: filter;
}

.bg-field .orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(80px);
  opacity: var(--orb-op);
  will-change: transform;
  transition: opacity 0.3s ease;
}

.bg-field .o1 {
  width: 720px; height: 720px;
  left: -10%; top: -20%;
  background: var(--brand-cyan);
}
.bg-field .o2 {
  width: 660px; height: 660px;
  right: -8%; top: -4%;
  background: var(--brand-violet);
}
.bg-field .o3 {
  width: 760px; height: 760px;
  left: 28%; bottom: -32%;
  background: var(--brand-pink);
}
.bg-field .o4 {
  width: 620px; height: 620px;
  left: -6%; bottom: -12%;
  background: var(--brand-blue);
}

/* Crisp gradient rings — refraction edges as glass passes over them */
.bg-field .ring {
  position: absolute;
  border-radius: 50%;
  background: conic-gradient(from 90deg, #20C1DC, #2E96F5, #A766F0, #F66DB9, #20C1DC);
  -webkit-mask: radial-gradient(closest-side, transparent 63%, #000 64%);
  mask: radial-gradient(closest-side, transparent 63%, #000 64%);
  filter: blur(1.5px);
  opacity: var(--ring-op);
  will-change: transform;
  transition: opacity 0.3s ease;
}
.bg-field .r1 {
  width: 560px; height: 560px;
  left: 46%; top: 8%;
}
.bg-field .r2 {
  width: 440px; height: 440px;
  left: 6%; top: 52%;
}

/* ============ FONT ROLES — Safari vs other browsers ============ */
/* Roles: --font-en (English body) / --font-zh (Chinese body) /
   --font-title (card titles) / --font-code (code & mono fields) */
:root {
  --font-en: "Segoe UI", "Helvetica Neue", Helvetica, Arial, sans-serif;
  --font-zh: "Microsoft YaHei UI", "Microsoft YaHei", sans-serif;
  --font-title: Georgia, "Times New Roman", serif;
  --font-code: Consolas, "Courier New", monospace;
}
html[data-browser="safari"] {
  --font-en: -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro Display", sans-serif;
  --font-zh: "PingFang SC", sans-serif;
  --font-title: Georgia, "Times New Roman", serif;
  --font-code: "SF Mono", ui-monospace, Menlo, monospace;
}

body { font-family: var(--font-en), var(--font-zh), sans-serif; }
.mono, .col code, code { font-family: var(--font-code); }
.card h3, .col h3 { font-family: var(--font-title), var(--font-zh), serif; }

/* ============ PAGED SCROLL — book-like snap ============ */
html { scroll-snap-type: y proximity; }

.page {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  scroll-snap-align: start;
  scroll-snap-stop: always;
  padding-top: 64px;
  padding-bottom: 64px;
}
.footer { scroll-snap-align: end; }

/* Staggered fade/slide for page content — in when snapped, out when leaving */
.page .fx {
  opacity: 0;
  transform: translateY(28px);
  transition:
    opacity 0.7s var(--ease-out-expo),
    transform 0.7s var(--ease-out-expo);
  transition-delay: var(--fd, 0s);
}
.page.in .fx {
  opacity: 1;
  transform: translateY(0);
}

/* ============ LANGUAGE TOGGLE ============ */
.lang-toggle {
  height: 34px;
  min-width: 44px;
  padding: 0 12px;
  border: none;
  border-radius: 999px;
  background: var(--glass-bg);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  backdrop-filter: blur(20px) saturate(180%);
  box-shadow:
    inset 0 1px 0 0 var(--glass-spec),
    inset 0 -1px 0 0 var(--glass-shade),
    inset 0 0 0 1px var(--glass-edge);
  color: var(--text-2);
  font-family: var(--font-code);
  font-size: 12px;
  letter-spacing: 0.04em;
  cursor: pointer;
  transition: color 0.15s ease, transform 0.15s ease;
}
.lang-toggle:hover { color: var(--text); }
.lang-toggle:active { transform: scale(0.94); }

/* ============ PAGED SCROLL — mobile fallback ============ */
@media (max-width: 900px) {
  html { scroll-snap-type: none; }
  .page { min-height: 0; padding-top: 0; padding-bottom: 0; }
  .page .fx { opacity: 1; transform: none; transition: none; }
}

/* ===== v6 修订：①上下文页压缩 ②小字加大+对比度 ③复制按钮 ⑤hero单行 ⑥光晕层级 ===== */

/* ① 上下文页整体压缩，保证一屏完整显示 */
.rows { padding: 8px 40px; margin-top: 36px; }
.row { padding: 24px 0; }
.thread-divider { padding: 40px 0; }
.thread-divider svg { height: 40px; }
.divider-caption { margin-top: 16px; }

/* ② 小字加大 */
.mono { font-size: 13px; }
.steps li { font-size: 16px; }
.footnotes p { font-size: 13.5px; color: var(--text-2); }
.spec-key { font-size: 14px; color: var(--text-2); }
.sec-item p { font-size: 14px; }
.col p { font-size: 15px; }
.divider-caption { font-size: 13px; }

/* ② 白天模式对比度加深 */
:root, [data-theme="light"] {
  --text-2: rgba(29, 29, 31, 0.72);
  --text-3: rgba(29, 29, 31, 0.66);
}
[data-theme="dark"] {
  --text-2: rgba(245, 245, 247, 0.68);
  --text-3: rgba(245, 245, 247, 0.5);
}

/* ③ 代码行 + 液态玻璃复制按钮 */
.code-row { display: flex; align-items: center; gap: 10px; }
.code-row > code, .code-row > pre, .code-row > .code-block { flex: 1; min-width: 0; }
.copy-btn {
  position: relative;
  flex: 0 0 auto;
  width: 34px; height: 34px;
  border-radius: 50%;
  border: 1px solid var(--glass-border, rgba(255,255,255,0.25));
  background: var(--glass-bg);
  -webkit-backdrop-filter: blur(20px) saturate(1.6);
  backdrop-filter: blur(20px) saturate(1.6);
  box-shadow:
    inset 0 1px 0 rgba(255,255,255,0.35),
    inset 0 -1px 0 rgba(0,0,0,0.08),
    0 4px 14px rgba(0,0,0,0.12);
  cursor: pointer;
  display: inline-flex; align-items: center; justify-content: center;
  color: var(--text);
  transition: transform .25s ease, box-shadow .25s ease;
}
.copy-btn:hover { transform: scale(1.08); }
.copy-btn:active { transform: scale(0.96); }
.copy-btn.copy-failed { outline: 2px solid #d1495b; outline-offset: 2px; }
.copy-btn svg {
  position: absolute; inset: 0; margin: auto;
  width: 15px; height: 15px;
  transition: opacity .25s ease, transform .25s ease;
}
.copy-btn .icon-check { opacity: 0; transform: scale(0.6); color: #20C1DC; }
.copy-btn.copied .icon-copy { opacity: 0; transform: scale(0.6); }
.copy-btn.copied .icon-check { opacity: 1; transform: scale(1); }

/* ⑤ hero 单行标题 + 线标上移 */
.hero-title { font-size: clamp(40px, 7.2vw, 84px); white-space: nowrap; }
.hero-mark { margin-top: 36px; width: min(480px, 70vw); }

@media (max-width: 520px) {
  .hero { padding: 112px 20px 64px; }
  .hero-title {
    font-size: clamp(28px, 8.2vw, 34px);
    letter-spacing: -0.035em;
  }
  .sec-grid { grid-template-columns: 1fr; }
}

/* ⑥ 光晕层置于文字层之下 */
.card::before, .col::before { z-index: 0; }
.card > *, .col > * { position: relative; z-index: 1; }

/* ③ 修订：代码行内容防溢出 */
.code-row > code { font-size: 11px; padding: 12px 12px; scrollbar-width: none; }
.code-row > code::-webkit-scrollbar { display: none; }

/* Keep accessibility fallbacks last so later component refinements cannot
   accidentally restore transparency or decorative effects. */
@media (prefers-reduced-transparency: reduce) {
  .nav,
  .glass,
  .card,
  .col,
  .rows,
  .spec,
  .statement .wrap,
  .theme-toggle,
  .lang-toggle,
  .copy-btn {
    -webkit-backdrop-filter: none;
    backdrop-filter: none;
    background: var(--bg-1);
  }
  .bg-field .orb,
  .bg-field .ring { opacity: 0.12; }
}

@media (prefers-contrast: more) {
  html[data-theme="dark"] {
    --text-2: #f5f5f7;
    --text-3: #d7d7dc;
    --hairline: rgba(255, 255, 255, 0.68);
    --nav-bg: #0d0d10;
    --glass-bg: #15151a;
    --glass-bg-strong: #15151a;
    --glass-edge: rgba(255, 255, 255, 0.72);
  }
  html[data-theme="light"] {
    --text-2: #1d1d1f;
    --text-3: #343438;
    --hairline: rgba(0, 0, 0, 0.62);
    --nav-bg: #ffffff;
    --glass-bg: #ffffff;
    --glass-bg-strong: #ffffff;
    --glass-edge: rgba(0, 0, 0, 0.62);
  }
  .nav,
  .glass,
  .card,
  .col,
  .rows,
  .spec,
  .statement .wrap,
  .theme-toggle,
  .lang-toggle,
  .copy-btn {
    -webkit-backdrop-filter: none;
    backdrop-filter: none;
    box-shadow: inset 0 0 0 1px var(--hairline);
  }
  .bg-field .orb,
  .bg-field .ring { opacity: 0.06; }
  a:focus-visible,
  button:focus-visible { outline-width: 4px; }
}

@media (forced-colors: active) {
  .bg-field,
  .card::before,
  .col::before,
  .card::after,
  .col::after,
  .rows::after,
  .spec::after,
  .statement .wrap::after { display: none; }
  .nav,
  .card,
  .col,
  .rows,
  .spec,
  .statement .wrap,
  .nav-cta,
  .btn-pill,
  .theme-toggle,
  .lang-toggle,
  .copy-btn {
    background: Canvas;
    color: CanvasText;
    border: 1px solid CanvasText;
    box-shadow: none;
  }
}