/* Active Matter Promo
   ui-ux-pro-max: Scroll-Triggered Storytelling + HUD/Sci-Fi FUI × Modern Dark Cinema
   Palette: quantum cyan (toned) on ash void — avoid harsh magenta neon overload
   Motion: stagger reveal 300–600ms, ease cubic-bezier(0.16,1,0.3,1) */

@import url("https://fonts.googleapis.com/css2?family=Exo+2:wght@400;500;600;700&family=Noto+Sans+SC:wght@300;400;500;600;700&display=swap");

:root {
  --bg: #070b12;
  --bg-elevated: #0e141e;
  --bg-soft: #141c28;
  --surface: rgba(110, 202, 216, 0.06);
  --primary: #6ecad8;
  --primary-deep: #2a8fa0;
  --primary-glow: rgba(110, 202, 216, 0.35);
  --accent: #9fe3ee;
  --accent-warm: #d4c4a8;
  --fg: #e8eef2;
  --fg-muted: #8b97a5;
  --border: rgba(110, 202, 216, 0.16);
  --border-strong: rgba(110, 202, 216, 0.38);
  --danger: #e85d5d;
  --ring: #6ecad8;

  --font-display: "Exo 2", "Noto Sans SC", sans-serif;
  --font-body: "Noto Sans SC", "Segoe UI", sans-serif;

  --ease: cubic-bezier(0.16, 1, 0.3, 1);
  --dur: 280ms;
  --dur-slow: 560ms;
  --nav-h: 4.25rem;
  --max: 74rem;
  --radius: 10px;
  --radius-sm: 6px;
}

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

html {
  scroll-behavior: smooth;
  color-scheme: dark;
}

body {
  margin: 0;
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.7;
  color: var(--fg);
  background: var(--bg);
  min-height: 100dvh;
  overflow-x: hidden;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -2;
  background:
    radial-gradient(ellipse 70% 45% at 15% 10%, rgba(42, 143, 160, 0.22), transparent 55%),
    radial-gradient(ellipse 55% 40% at 90% 30%, rgba(110, 202, 216, 0.1), transparent 50%),
    radial-gradient(ellipse 50% 35% at 50% 100%, rgba(20, 40, 55, 0.5), transparent 60%),
    linear-gradient(180deg, #060910 0%, var(--bg) 45%, #05080e 100%);
}

.ambient {
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  overflow: hidden;
}

.ambient__orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(60px);
  opacity: 0.14;
  animation: orb-drift 18s var(--ease) infinite alternate;
}

.ambient__orb--a {
  width: 28rem;
  height: 28rem;
  background: #2a8fa0;
  top: 10%;
  left: -8%;
}

.ambient__orb--b {
  width: 22rem;
  height: 22rem;
  background: #6ecad8;
  bottom: 15%;
  right: -6%;
  animation-delay: -6s;
  animation-duration: 22s;
}

@keyframes orb-drift {
  from {
    transform: translate(0, 0) scale(1);
  }
  to {
    transform: translate(4%, 6%) scale(1.08);
  }
}

img {
  max-width: 100%;
  height: auto;
  display: block;
  background: var(--bg-soft);
}

a {
  color: var(--primary);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
  transition: color var(--dur) var(--ease);
}

a:hover {
  color: var(--accent);
}

:focus-visible {
  outline: 2px solid var(--ring);
  outline-offset: 3px;
}

.skip-link {
  position: absolute;
  left: 1rem;
  top: -100px;
  z-index: 300;
  padding: 0.5rem 1rem;
  background: var(--primary);
  color: #061018;
  font-weight: 600;
  border-radius: var(--radius-sm);
}

.skip-link:focus {
  top: 1rem;
}

.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 2px;
  width: 0%;
  z-index: 200;
  background: linear-gradient(90deg, var(--primary-deep), var(--accent));
  box-shadow: 0 0 12px var(--primary-glow);
  pointer-events: none;
}

/* Nav */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-h);
  display: flex;
  align-items: center;
  backdrop-filter: blur(16px) saturate(1.2);
  background: rgba(7, 11, 18, 0.72);
  border-bottom: 1px solid var(--border);
  transition: background var(--dur) var(--ease), border-color var(--dur) var(--ease);
}

.site-nav.is-scrolled {
  background: rgba(7, 11, 18, 0.9);
  border-bottom-color: var(--border-strong);
}

.site-nav__inner {
  width: min(100% - 2rem, var(--max));
  margin-inline: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.brand {
  display: inline-flex;
  flex-direction: column;
  text-decoration: none;
  color: var(--fg);
  line-height: 1.15;
}

.brand__en {
  font-family: var(--font-display);
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  font-size: 0.92rem;
}

.brand__zh {
  font-size: 0.7rem;
  letter-spacing: 0.28em;
  color: var(--primary);
  font-weight: 500;
}

.nav-toggle {
  display: none;
  cursor: pointer;
  min-height: 44px;
  min-width: 44px;
  padding: 0.5rem 0.85rem;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--fg);
  font-family: var(--font-body);
  font-size: 0.85rem;
  transition: border-color var(--dur) var(--ease), background var(--dur) var(--ease);
}

.nav-toggle:hover {
  border-color: var(--border-strong);
  background: rgba(110, 202, 216, 0.12);
}

.nav-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.2rem 1rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav-links a {
  color: var(--fg-muted);
  text-decoration: none;
  font-size: 0.84rem;
  letter-spacing: 0.04em;
  padding: 0.45rem 0;
  position: relative;
  transition: color var(--dur) var(--ease);
}

.nav-links a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0.15rem;
  width: 100%;
  height: 1px;
  background: var(--primary);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--dur) var(--ease);
}

.nav-links a:hover,
.nav-links a[aria-current="true"] {
  color: var(--accent);
}

.nav-links a:hover::after,
.nav-links a[aria-current="true"]::after {
  transform: scaleX(1);
}

/* Layout */
.wrap {
  width: min(100% - 2rem, var(--max));
  margin-inline: auto;
}

.section {
  padding: clamp(3.5rem, 8vw, 6.5rem) 0;
  position: relative;
}

.section__eyebrow {
  font-family: var(--font-display);
  font-size: 0.72rem;
  letter-spacing: 0.28em;
  text-transform: uppercase;
  color: var(--primary);
  margin: 0 0 0.85rem;
  display: inline-flex;
  align-items: center;
  gap: 0.65rem;
}

.section__eyebrow::before {
  content: "";
  width: 1.5rem;
  height: 1px;
  background: var(--primary);
  opacity: 0.7;
}

.section__title {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(1.7rem, 3.4vw, 2.55rem);
  letter-spacing: 0.03em;
  line-height: 1.2;
  margin: 0 0 1rem;
}

.section__lead {
  max-width: 40rem;
  color: var(--fg-muted);
  margin: 0 0 2.25rem;
  font-size: 1.05rem;
}

/* Reveal */
.reveal {
  opacity: 0;
  transform: translateY(16px);
  transition: opacity var(--dur-slow) var(--ease), transform var(--dur-slow) var(--ease);
}

.reveal.is-visible {
  opacity: 1;
  transform: none;
}

.stagger > .stagger__item {
  opacity: 0;
  transform: translateY(14px);
  transition: opacity 0.48s var(--ease), transform 0.48s var(--ease);
}

.stagger.is-visible > .stagger__item {
  opacity: 1;
  transform: none;
}

.stagger.is-visible > .stagger__item:nth-child(1) {
  transition-delay: 0.04s;
}
.stagger.is-visible > .stagger__item:nth-child(2) {
  transition-delay: 0.1s;
}
.stagger.is-visible > .stagger__item:nth-child(3) {
  transition-delay: 0.16s;
}
.stagger.is-visible > .stagger__item:nth-child(4) {
  transition-delay: 0.22s;
}
.stagger.is-visible > .stagger__item:nth-child(5) {
  transition-delay: 0.28s;
}
.stagger.is-visible > .stagger__item:nth-child(6) {
  transition-delay: 0.34s;
}

/* Hero */
.hero {
  position: relative;
  min-height: calc(100dvh - var(--nav-h));
  display: grid;
  align-items: end;
  overflow: hidden;
}

.hero__media {
  position: absolute;
  inset: 0;
}

.hero__media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center 45%;
  transform: scale(1.04);
  animation: hero- ken 28s ease-in-out infinite alternate;
}

@keyframes hero-ken {
  from {
    transform: scale(1.04) translate(0, 0);
  }
  to {
    transform: scale(1.1) translate(-1.2%, 1%);
  }
}

.hero__scrim {
  position: absolute;
  inset: 0;
  background:
    linear-gradient(180deg, rgba(7, 11, 18, 0.25) 0%, rgba(7, 11, 18, 0.45) 40%, rgba(7, 11, 18, 0.94) 100%),
    linear-gradient(90deg, rgba(7, 11, 18, 0.78) 0%, rgba(7, 11, 18, 0.25) 55%, transparent 75%);
}

.hero__content {
  position: relative;
  z-index: 1;
  width: min(100% - 2rem, var(--max));
  margin: 0 auto;
  padding: 5.5rem 0 4rem;
}

.hero__brand {
  font-family: var(--font-display);
  font-size: clamp(2.4rem, 7.5vw, 4.8rem);
  font-weight: 700;
  letter-spacing: 0.04em;
  line-height: 0.98;
  margin: 0 0 0.75rem;
  text-shadow: 0 4px 40px rgba(0, 0, 0, 0.55);
}

.hero__brand span {
  display: block;
  margin-top: 0.35em;
  font-size: 0.38em;
  letter-spacing: 0.32em;
  color: var(--primary);
  font-weight: 600;
}

.hero__headline {
  font-size: clamp(1.05rem, 2vw, 1.3rem);
  font-weight: 500;
  max-width: 28rem;
  margin: 0 0 0.75rem;
}

.hero__sub {
  max-width: 34rem;
  color: var(--fg-muted);
  margin: 0 0 1.75rem;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
  min-height: 48px;
  padding: 0.8rem 1.4rem;
  font-family: var(--font-body);
  font-size: 0.92rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  border-radius: var(--radius-sm);
  border: 1px solid transparent;
  cursor: pointer;
  text-decoration: none;
  transition: background var(--dur) var(--ease), color var(--dur) var(--ease), border-color var(--dur) var(--ease),
    box-shadow var(--dur) var(--ease), transform var(--dur) var(--ease);
}

.btn:active {
  transform: scale(0.98);
}

.btn--primary {
  background: linear-gradient(135deg, #7ed4e0, #3aa8b8);
  color: #061018;
  box-shadow: 0 0 0 0 transparent;
}

.btn--primary:hover {
  color: #061018;
  box-shadow: 0 0 28px var(--primary-glow);
}

.btn--ghost {
  background: rgba(14, 20, 30, 0.55);
  border-color: var(--border-strong);
  color: var(--fg);
  backdrop-filter: blur(8px);
}

.btn--ghost:hover {
  border-color: var(--primary);
  color: var(--accent);
  background: rgba(110, 202, 216, 0.1);
}

/* Pillars / feature strip */
.pillars {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr));
  gap: 1.25rem;
}

.pillar {
  padding: 1.35rem 1.25rem;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--border);
  transition: border-color var(--dur) var(--ease), transform var(--dur) var(--ease), background var(--dur) var(--ease);
}

.pillar:hover {
  border-color: var(--border-strong);
  background: rgba(110, 202, 216, 0.09);
  transform: translateY(-3px);
}

.pillar__icon {
  width: 2rem;
  height: 2rem;
  margin-bottom: 0.85rem;
  color: var(--primary);
}

.pillar h3 {
  font-family: var(--font-display);
  font-size: 1.1rem;
  letter-spacing: 0.04em;
  margin: 0 0 0.45rem;
}

.pillar p {
  margin: 0;
  color: var(--fg-muted);
  font-size: 0.94rem;
}

/* Nested accordion */
.tree {
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.tree__item {
  border: 1px solid var(--border);
  background: rgba(14, 20, 30, 0.82);
  border-radius: var(--radius);
  overflow: clip;
  transition: border-color var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.tree__item[open] {
  border-color: var(--border-strong);
  box-shadow: 0 0 0 1px rgba(110, 202, 216, 0.08), 0 12px 40px rgba(0, 0, 0, 0.25);
}

.tree__summary {
  list-style: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 1.05rem 1.2rem;
  min-height: 52px;
  font-weight: 600;
  transition: background var(--dur) var(--ease);
}

.tree__summary::-webkit-details-marker {
  display: none;
}

.tree__summary:hover {
  background: rgba(110, 202, 216, 0.07);
}

.tree__chevron {
  width: 1.1rem;
  height: 1.1rem;
  flex-shrink: 0;
  color: var(--primary);
  transition: transform var(--dur) var(--ease);
}

details[open] > .tree__summary .tree__chevron {
  transform: rotate(180deg);
}

.tree__body {
  padding: 0 1.2rem 1.2rem;
  color: var(--fg-muted);
  border-top: 1px solid rgba(255, 255, 255, 0.04);
}

.tree__body > :first-child {
  margin-top: 1rem;
}

.tree--nested {
  margin-top: 1rem;
  gap: 0.5rem;
}

.tree--nested .tree__item {
  background: rgba(7, 11, 18, 0.65);
  border-radius: var(--radius-sm);
}

.tree--nested .tree__summary {
  font-size: 0.94rem;
  font-weight: 500;
  min-height: 44px;
  padding: 0.8rem 1rem;
}

/* Flow */
.flow {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(10rem, 1fr));
  gap: 0.75rem;
  margin: 0 0 2rem;
}

.flow__step {
  padding: 1.15rem 1rem;
  border-radius: var(--radius-sm);
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-top: 2px solid var(--primary-deep);
  transition: transform var(--dur) var(--ease), border-color var(--dur) var(--ease);
}

.flow__step:hover {
  transform: translateY(-2px);
  border-color: var(--border-strong);
}

.flow__step strong {
  display: block;
  font-family: var(--font-display);
  letter-spacing: 0.1em;
  color: var(--primary);
  font-size: 0.78rem;
  margin-bottom: 0.45rem;
}

.flow__step p {
  margin: 0;
  font-size: 0.9rem;
  color: var(--fg-muted);
}

/* Media chapters */
.chapter {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr);
  gap: 0;
  border-radius: var(--radius);
  overflow: hidden;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  margin-bottom: 1.25rem;
}

.chapter--flip {
  direction: rtl;
}

.chapter--flip > * {
  direction: ltr;
}

.chapter__media {
  position: relative;
  min-height: 240px;
  overflow: hidden;
}

.chapter__media img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.8s var(--ease);
}

.chapter:hover .chapter__media img {
  transform: scale(1.05);
}

.chapter__body {
  padding: clamp(1.25rem, 3vw, 2rem);
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.chapter__tag {
  font-family: var(--font-display);
  font-size: 0.72rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--primary);
  margin-bottom: 0.65rem;
}

.chapter__body h3 {
  font-family: var(--font-display);
  font-size: 1.35rem;
  margin: 0 0 0.65rem;
  letter-spacing: 0.03em;
}

.chapter__body p {
  margin: 0;
  color: var(--fg-muted);
}

/* Split highlight */
.highlight-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(16rem, 1fr));
  gap: 1rem;
  margin-top: 1.5rem;
}

.highlight {
  padding: 1.35rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: linear-gradient(160deg, rgba(110, 202, 216, 0.08), rgba(14, 20, 30, 0.4));
}

.highlight h3 {
  font-family: var(--font-display);
  margin: 0 0 0.5rem;
  font-size: 1.05rem;
}

.highlight p {
  margin: 0;
  color: var(--fg-muted);
  font-size: 0.94rem;
}

/* Climax */
.climax {
  text-align: center;
  padding: clamp(4rem, 10vw, 7rem) 0;
  border-block: 1px solid var(--border);
  background:
    radial-gradient(ellipse 55% 70% at 50% 100%, rgba(42, 143, 160, 0.22), transparent 65%),
    var(--bg-elevated);
}

.climax h2 {
  font-family: var(--font-display);
  font-size: clamp(1.55rem, 3vw, 2.2rem);
  letter-spacing: 0.04em;
  margin: 0 0 0.85rem;
}

.climax p {
  max-width: 36rem;
  margin: 0 auto 1.75rem;
  color: var(--fg-muted);
}

.climax .cta-row {
  justify-content: center;
}

/* Footer */
.site-footer {
  padding: 3rem 0 2.5rem;
  color: var(--fg-muted);
  font-size: 0.85rem;
}

.site-footer p {
  margin: 0 0 0.75rem;
  max-width: 48rem;
}

.site-footer small {
  opacity: 0.75;
}

/* Responsive */
@media (max-width: 900px) {
  .nav-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }

  .nav-links {
    display: none;
    position: absolute;
    top: var(--nav-h);
    left: 0;
    right: 0;
    flex-direction: column;
    gap: 0;
    padding: 0.75rem 1.25rem 1.25rem;
    background: rgba(7, 11, 18, 0.96);
    border-bottom: 1px solid var(--border);
    backdrop-filter: blur(16px);
  }

  .nav-links.is-open {
    display: flex;
  }

  .nav-links a {
    min-height: 44px;
    display: flex;
    align-items: center;
  }

  .chapter,
  .chapter--flip {
    grid-template-columns: 1fr;
    direction: ltr;
  }

  .chapter__media {
    aspect-ratio: 16 / 9;
    min-height: 0;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  .ambient__orb,
  .hero__media img {
    animation: none !important;
  }

  .reveal,
  .stagger > .stagger__item {
    opacity: 1;
    transform: none;
    transition: none;
  }

  .chapter:hover .chapter__media img,
  .pillar:hover,
  .flow__step:hover {
    transform: none;
  }

  .btn,
  .tree__summary,
  .tree__chevron,
  .nav-links a::after {
    transition: none;
  }
}