/* ============================================
   COCO Matrix — v0 site
   Colors / type sourced from "COCO Matrix 品牌视觉系统方案" (Match Studio, 2026-06-29)
   NOTE: Brand typeface is OPPO Sans 4.0 — web-embed license not yet confirmed.
   Using a close system-font stack for now; swap in OPPO Sans once cleared.
   ============================================ */

:root {
  --blue: #92CEFF;
  --blue-light: #D2ECFF;
  --dark: #353535;
  --black: #131415;
  --cream: #FFFBF5;
  --pink: #FCDBFA;
  --yellow: #EDF2C2;
  --coral: #FCD9D9;

  --font: "PingFang SC", "HarmonyOS Sans SC", "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;

  --container: 1120px;
  --radius: 20px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; overflow-x: clip; }

body {
  margin: 0;
  font-family: var(--font);
  color: var(--black);
  background: var(--cream);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

img { max-width: 100%; display: block; }

.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
}

a { color: inherit; text-decoration: none; }

h1, h2, h3 { margin: 0; font-weight: 600; letter-spacing: -0.01em; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 13px 26px;
  border-radius: 999px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: transform .15s ease, background .15s ease, opacity .15s ease;
  white-space: nowrap;
}
.btn:hover { transform: translateY(-1px); }
.btn-primary { background: var(--black); color: #fff; }
.btn-primary:hover { background: var(--dark); }
.btn-ghost { background: transparent; color: var(--black); border: 1.5px solid var(--black); }
.btn-ghost:hover { background: var(--black); color: #fff; }
.btn-small { padding: 10px 20px; font-size: 14px; margin-top: 16px; }

/* ---------- Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 251, 245, 0.9);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(19,20,21,0.06);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 14px;
  padding-bottom: 14px;
  gap: 24px;
}
.brand { display: flex; align-items: center; }
.brand-logo { height: 28px; width: auto; }
.hero-copy { min-width: 0; }
.values-grid { margin-top: 0; }
.main-nav { display: flex; gap: 32px; font-size: 15px; font-weight: 500; }
.main-nav a { opacity: .78; transition: opacity .15s ease; }
.main-nav a:hover { opacity: 1; }
.nav-mobile-only { display: none; }
.header-actions { display: flex; align-items: center; gap: 14px; }

.lang-toggle {
  font-size: 13px;
  font-weight: 600;
  letter-spacing: .02em;
  color: var(--black);
  background: none;
  border: 1px solid color-mix(in srgb, var(--black) 16%, transparent);
  border-radius: 999px;
  padding: 7px 14px;
  cursor: pointer;
  transition: border-color .15s ease, background .15s ease;
  white-space: nowrap;
}
.lang-toggle:hover { border-color: color-mix(in srgb, var(--black) 40%, transparent); background: color-mix(in srgb, var(--black) 5%, transparent); }

/* header "Contact us" pill matches the language-toggle pill's outline
   style AND size (same padding/font-size, not just the same colors) */
.header-contact-btn {
  background: transparent;
  color: var(--black);
  border: 1px solid color-mix(in srgb, var(--black) 16%, transparent);
  padding: 7px 14px;
  font-size: 13px;
}
.header-contact-btn:hover {
  background: color-mix(in srgb, var(--black) 5%, transparent);
  border-color: color-mix(in srgb, var(--black) 40%, transparent);
}

.nav-burger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 32px;
  height: 32px;
  background: none;
  border: none;
  cursor: pointer;
}
.nav-burger span { display: block; height: 2px; background: var(--black); border-radius: 2px; }

/* ---------- Hero ---------- */
/* The copy scrolls away over a sticky video before the next section enters. */
.hero-scroll-track { position: relative; height: 220vh; background: var(--black); }
.hero-bg-pin { position: sticky; top: 63px; z-index: 0; }
/* the video sits in normal flow at width:100% / height:auto, so it's
   always scaled proportionally to page width and its own rendered
   height is what the pinned box's height ends up being — the video's
   first frame (assets/hero-poster-0901.jpg) is its poster, so "the cover" is
   literally the video's own cover, not a separate photo. */
.hero-photo {
  position: relative;
  overflow: hidden;
  color: #fff;
  background: var(--black); /* fallback fill behind short/narrow video */
  min-height: 420px;
}
.hero-bg { position: relative; z-index: 0; }
.hero-bg video {
  display: block;
  width: 100%;
  height: auto;
}
.hero-copy-layer {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100vh;
  z-index: 2;
  display: flex;
  align-items: center;
  justify-content: center;
  pointer-events: none;
  transition: opacity .35s ease;
}
.hero-scroll-track.is-playing .hero-copy-layer { opacity: 0; }
/* Keep foreground text readable over the moving video. */
.hero-scrim {
  position: absolute;
  inset: 0;
  z-index: 0;
  background:
    linear-gradient(180deg, rgba(19,20,21,.42) 0%, rgba(19,20,21,.5) 45%, rgba(19,20,21,.78) 100%);
}
.hero-copy-layer .hero-inner { position: relative; z-index: 1; width: 100%; pointer-events: auto; }
.hero-copy {
  max-width: 900px;
  width: 100%;
  margin: 0 auto;
  text-align: center;
}
@media (prefers-reduced-motion: reduce) {
  .hero-scroll-track { height: auto; }
  .hero-bg-pin { position: static; }
  .hero-copy-layer { position: static; height: auto; padding: 140px 0 96px; }
}
.eyebrow {
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: #fff;
  opacity: .85;
  margin: 0 0 22px;
  text-shadow: 0 1px 3px rgba(0,0,0,.5), 0 2px 14px rgba(0,0,0,.35);
}
.hero-copy h1 {
  display: inline-block;
  max-width: 100%;
  font-size: clamp(20px, 3.4vw, 38px);
  line-height: 1.3;
  font-weight: 600;
  letter-spacing: 0.06em;
  white-space: nowrap;
  text-align: center;
  color: #fff;
  margin: 0 auto 26px;
  transform-origin: center top;
  text-shadow: 0 1px 3px rgba(0,0,0,.5), 0 2px 14px rgba(0,0,0,.35);
}
.hero-tag {
  font-size: 16px;
  line-height: 1.6;
  color: #fff;
  opacity: .92;
  margin: 0 auto 36px;
  max-width: 46ch;
  text-shadow: 0 1px 3px rgba(0,0,0,.5), 0 2px 14px rgba(0,0,0,.35);
}
.hero-actions { display: flex; gap: 14px; flex-wrap: wrap; justify-content: center; }
.hero-photo .btn-ghost {
  color: #fff;
  border-color: rgba(255,255,255,0.7);
  background: rgba(19,20,21,.28);
  backdrop-filter: blur(6px);
}
.hero-photo .btn-ghost:hover { background: #fff; color: var(--black); }
.hero-sound-toggle {
  position: absolute;
  right: clamp(16px, 2.5vw, 36px);
  bottom: clamp(16px, 2.5vw, 30px);
  z-index: 4;
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  padding: 0;
  border: 1px solid rgba(255,255,255,.42);
  border-radius: 999px;
  color: #fff;
  background: rgba(19,20,21,.42);
  backdrop-filter: blur(8px);
  font: inherit;
  font-size: 13px;
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transition: opacity .25s ease, background .2s ease, border-color .2s ease;
}
.hero-scroll-track.is-playing .hero-sound-toggle { opacity: 1; visibility: visible; pointer-events: auto; }
.hero-sound-toggle span { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
.hero-sound-toggle:hover { background: rgba(19,20,21,.68); border-color: rgba(255,255,255,.7); }
.hero-sound-toggle:focus-visible { outline: 2px solid #fff; outline-offset: 3px; }
.hero-sound-toggle svg { width: 20px; height: 20px; fill: currentColor; }
.hero-sound-toggle .sound-waves,
.hero-sound-toggle .sound-slash { fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; }
.hero-sound-toggle[aria-pressed="false"] .sound-waves,
.hero-sound-toggle[aria-pressed="true"] .sound-slash { display: none; }

/* ---------- About ---------- */
.about { padding: 88px 0; }
.section-label {
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--dark);
  opacity: .55;
  margin: 0 0 18px;
}
.section-label--light { color: #fff; opacity: .55; }

.about-heading {
  font-size: clamp(28px, 3.6vw, 38px);
  margin-bottom: 28px;
}

.about-lead {
  font-size: 18px;
  line-height: 1.75;
  max-width: 78ch;
  color: var(--dark);
  margin: 0 0 20px;
}
.about-lead:last-of-type { margin-bottom: 56px; }
.about-lead--mission {
  font-size: 22px;
  font-weight: 700;
  color: var(--black);
  letter-spacing: 0.01em;
}

.values-kicker {
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--dark);
  opacity: .55;
  margin-bottom: 22px;
}
.values-cards {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: rgba(19,20,21,0.08);
  border: 1px solid rgba(19,20,21,0.08);
  border-radius: var(--radius);
  overflow: hidden;
}
.value-card {
  position: relative;
  background: var(--cream);
  padding: 32px 24px 26px;
  transition: background .2s ease;
}
.value-card::before {
  content: "";
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 2px;
  background: var(--black);
  opacity: .35;
  transition: opacity .2s ease, background .2s ease;
}
.value-card:hover { background: #fff; }
.value-card:hover::before { opacity: 1; background: var(--blue); }
.value-card:nth-child(2):hover::before { background: #C99BC0; }
.value-card:nth-child(3):hover::before { background: #A3AE63; }
.value-card:nth-child(4):hover::before { background: #D18E88; }
.value-card h3 {
  font-size: 17px;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin-bottom: 10px;
}
.value-card p { font-size: 14px; color: var(--dark); opacity: .7; line-height: 1.6; margin: 0; }

.founders-line {
  margin-top: 40px;
  font-size: 15px;
  color: var(--dark);
  opacity: .75;
}

/* ---------- Brand grid / dot motif ---------- */
.dot-grid { position: relative; }
.dot-grid::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image: radial-gradient(rgba(146,206,255,0.55) 1.4px, transparent 1.5px);
  background-size: 26px 26px;
  -webkit-mask-image: radial-gradient(ellipse 75% 65% at 50% 8%, #000 5%, transparent 78%);
  mask-image: radial-gradient(ellipse 75% 65% at 50% 8%, #000 5%, transparent 78%);
  opacity: .35;
}
.dot-grid > * { position: relative; z-index: 1; }

.grid-dark { position: relative; }
.grid-dark::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image: radial-gradient(rgba(146,206,255,0.16) 1.3px, transparent 1.4px);
  background-size: 30px 30px;
  -webkit-mask-image: radial-gradient(ellipse 85% 70% at 50% 0%, #000 5%, transparent 75%);
  mask-image: radial-gradient(ellipse 85% 70% at 50% 0%, #000 5%, transparent 75%);
}
.grid-dark > * { position: relative; z-index: 1; }

/* ---------- What We Build ---------- */
.build { padding: 88px 0; }
.build .section-label { margin-bottom: 32px; }

/* ---- animated capability diagram (robotics-four-dimensions) ---- */
#robotics-four-dimensions {
  /* four capability accents — same muted accent set used for the
     About/values hover states */
  --c1: var(--blue);     /* 01 · World Model Representation */
  --c2: #C99BC0;         /* 02 · In-Context Learning     */
  --c3: #A3AE63;         /* 03 · Learn from Human        */
  --c4: #D18E88;         /* 04 · Human-Robot Collaboration */
  --border: rgba(19,20,21,0.16);
  --muted: rgba(19,20,21,0.68);
  --card: rgba(19,20,21,0.05);
  width: 100%;
  color: var(--black);
}
#robotics-four-dimensions .rv-stage {
  position: relative;
  width: 100%;
  overflow: hidden;
  isolation: isolate;
  border-radius: 20px;
}
#robotics-four-dimensions .rv-desktop { display: block; width: 100%; height: auto; aspect-ratio: 760 / 470; }
#robotics-four-dimensions .rv-mobile { display: none; }

#robotics-four-dimensions .rv-scene-line { stroke: var(--border); stroke-width: 1.2; fill: none; }
#robotics-four-dimensions .rv-connection {
  fill: none;
  stroke: color-mix(in srgb, var(--black) 16%, transparent);
  stroke-width: 1.5;
  stroke-dasharray: 5 8;
  transition: stroke .6s ease, stroke-width .6s ease, opacity .6s ease;
  animation: rv-connection-drift 9s linear infinite;
}
#robotics-four-dimensions .rv-flow { fill: none; stroke-width: 3; stroke-linecap: round; stroke-dasharray: 18 240; opacity: 0; }
#robotics-four-dimensions .rv-node-shell { stroke: var(--border); stroke-width: 1.5; transition: fill .6s ease, stroke .6s ease, filter .6s ease; }
#robotics-four-dimensions .rv-node-title,
#robotics-four-dimensions .rv-core-copy,
#robotics-four-dimensions .rv-scene-label { fill: var(--black); font-family: inherit; }
#robotics-four-dimensions .rv-scene-label { font-size: 10.5px; font-weight: 600; letter-spacing: .12em; fill: var(--muted); }
#robotics-four-dimensions .rv-node-title { font-size: 16px; font-weight: 700; letter-spacing: -0.01em; }
#robotics-four-dimensions .rv-core-copy { font-size: 13px; font-weight: 700; letter-spacing: .1em; }
#robotics-four-dimensions .rv-icon-line { fill: none; stroke: currentColor; stroke-width: 1.7; stroke-linecap: round; stroke-linejoin: round; }
#robotics-four-dimensions .rv-core-orbit { transform-origin: 380px 230px; animation: rv-orbit 18s linear infinite; }
#robotics-four-dimensions .rv-pulse { transform-origin: 380px 230px; animation: rv-pulse 2.6s ease-out infinite; }
#robotics-four-dimensions .rv-robot { animation: rv-float 2.8s ease-in-out infinite; transform-origin: 380px 230px; }
#robotics-four-dimensions .rv-core-glow { transform-origin: 380px 230px; animation: rv-glow-breathe 4.5s ease-in-out infinite; }

/* cards light up on hover; hovering one dims the rest and plays its video full-screen */
#robotics-four-dimensions .rv-step { cursor: pointer; opacity: 1; transition: opacity .3s ease; }
#robotics-four-dimensions .rv-stage:hover .rv-step { opacity: .55; }
#robotics-four-dimensions .rv-step:hover { opacity: 1; }
#robotics-four-dimensions .rv-step-0:hover .rv-node-shell { fill: color-mix(in srgb, var(--c1) 16%, var(--cream)); stroke: color-mix(in srgb, var(--c1) 55%, transparent); filter: drop-shadow(0 8px 16px color-mix(in srgb, var(--c1) 20%, transparent)); }
#robotics-four-dimensions .rv-step-1:hover .rv-node-shell { fill: color-mix(in srgb, var(--c2) 16%, var(--cream)); stroke: color-mix(in srgb, var(--c2) 55%, transparent); filter: drop-shadow(0 8px 16px color-mix(in srgb, var(--c2) 20%, transparent)); }
#robotics-four-dimensions .rv-step-2:hover .rv-node-shell { fill: color-mix(in srgb, var(--c3) 16%, var(--cream)); stroke: color-mix(in srgb, var(--c3) 55%, transparent); filter: drop-shadow(0 8px 16px color-mix(in srgb, var(--c3) 20%, transparent)); }
#robotics-four-dimensions .rv-step-3:hover .rv-node-shell { fill: color-mix(in srgb, var(--c4) 16%, var(--cream)); stroke: color-mix(in srgb, var(--c4) 55%, transparent); filter: drop-shadow(0 8px 16px color-mix(in srgb, var(--c4) 20%, transparent)); }
#robotics-four-dimensions .rv-stage:has(.rv-step-0:hover) .rv-flow-0,
#robotics-four-dimensions .rv-stage:has(.rv-step-1:hover) .rv-flow-1,
#robotics-four-dimensions .rv-stage:has(.rv-step-2:hover) .rv-flow-2,
#robotics-four-dimensions .rv-stage:has(.rv-step-3:hover) .rv-flow-3 { opacity: 1; animation: rv-flow 2.4s linear infinite; }
#robotics-four-dimensions .rv-flow-0 { stroke: var(--c1); }
#robotics-four-dimensions .rv-flow-1 { stroke: var(--c2); }
#robotics-four-dimensions .rv-flow-2 { stroke: var(--c3); }
#robotics-four-dimensions .rv-flow-3 { stroke: var(--c4); }

/* hub logo + pulse ring tint to match whichever card is hovered
   (desktop hub and mobile core share this behavior) */
#robotics-four-dimensions .rv-tint-flood,
#robotics-four-dimensions .rv-tint-flood-m { flood-color: var(--black); transition: flood-color 1s ease; }
#robotics-four-dimensions .rv-pulse { transition: stroke 1s ease; }
#robotics-four-dimensions .rv-stage:has(.rv-step-0:hover) .rv-tint-flood,
#robotics-four-dimensions .rv-stage:has(.rv-step-0:hover) .rv-pulse { flood-color: var(--c1); stroke: var(--c1); }
#robotics-four-dimensions .rv-stage:has(.rv-step-1:hover) .rv-tint-flood,
#robotics-four-dimensions .rv-stage:has(.rv-step-1:hover) .rv-pulse { flood-color: var(--c2); stroke: var(--c2); }
#robotics-four-dimensions .rv-stage:has(.rv-step-2:hover) .rv-tint-flood,
#robotics-four-dimensions .rv-stage:has(.rv-step-2:hover) .rv-pulse { flood-color: var(--c3); stroke: var(--c3); }
#robotics-four-dimensions .rv-stage:has(.rv-step-3:hover) .rv-tint-flood,
#robotics-four-dimensions .rv-stage:has(.rv-step-3:hover) .rv-pulse { flood-color: var(--c4); stroke: var(--c4); }

@keyframes rv-orbit { to { transform: rotate(360deg); } }
@keyframes rv-pulse {
  0% { transform: scale(.85); opacity: .9; }
  70% { transform: scale(1.4); opacity: 0; }
  100% { opacity: 0; }
}
@keyframes rv-float { 0%,100% { transform: translateY(0); } 50% { transform: translateY(-5px); } }
@keyframes rv-flow { to { stroke-dashoffset: -258; } }
@keyframes rv-glow-breathe {
  0%, 100% { transform: scale(1); opacity: .85; }
  50% { transform: scale(1.06); opacity: 1; }
}
@keyframes rv-connection-drift { to { stroke-dashoffset: -13; } }

/* ---- hover-triggered video overlay: fills the whole diagram "screen"
   (.rv-stage). No black backdrop — outside the growing video circle the
   SVG diagram stays visible the whole time. On hover-in, the reveal
   waits INTRO_DELAY (1s, matching the full flow-line travel + hub-tint
   color change below) so that intro plays out completely, unobscured,
   before the video appears — as an iris reveal anchored on the hub logo,
   a circle growing outward from the hub's exact position (50%, 49% of
   the stage, matching the SVG's cx=380/cy=230 center) until it covers
   the full stage. Closing (hover-out) has no delay, so it feels
   responsive. Driven purely by the .is-active / :has(.is-active)
   transitions below; JS only starts/stops <video> playback. ---- */
#robotics-four-dimensions .rv-video-overlay {
  position: absolute;
  inset: 0;
  z-index: 5;
  pointer-events: none;
  opacity: 0;
  transition: opacity .5s ease; /* closing: fast, no delay */
}
#robotics-four-dimensions .rv-video-overlay:has(.is-active) {
  opacity: 1;
  transition: opacity .25s ease;
}
#robotics-four-dimensions .rv-overlay-video {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  /* fill the whole stage screen edge-to-edge while hovered */
  object-fit: cover;
  opacity: 0;
  clip-path: circle(0% at 50% 49%);
  filter: brightness(.55);
  transition:
    opacity .6s ease,
    clip-path 1.5s cubic-bezier(.32,.72,.23,1),
    filter .9s ease;
}
#robotics-four-dimensions .rv-overlay-video.is-active {
  opacity: 1;
  clip-path: circle(150% at 50% 49%);
  filter: brightness(1);
  transition:
    opacity .3s ease,
    clip-path .8s cubic-bezier(.32,.72,.23,1),
    filter .5s ease;
}
#robotics-four-dimensions .rv-video-overlay::after {
  /* subtle projector vignette so the video reads as "playing on the hub screen" */
  content: "";
  position: absolute;
  inset: 0;
  pointer-events: none;
  background: radial-gradient(ellipse at 50% 50%, transparent 55%, rgba(0,0,0,.35) 100%);
  opacity: 0;
  transition: opacity .9s ease;
}
#robotics-four-dimensions .rv-video-overlay:has(.is-active)::after { opacity: 1; transition: opacity .5s ease; }
@media (max-width: 520px) {
  #robotics-four-dimensions .rv-video-overlay { display: none; }
}
@media (prefers-reduced-motion: reduce), (hover: none), (pointer: coarse) {
  #robotics-four-dimensions .rv-video-overlay,
  #robotics-four-dimensions .rv-overlay-video { display: none; }
}

/* ---------- Scroll reveal ---------- */
.reveal {
  opacity: 0;
  transform: translateY(22px);
  transition: opacity .7s cubic-bezier(.2,.7,.2,1), transform .7s cubic-bezier(.2,.7,.2,1);
  will-change: opacity, transform;
}
.reveal.is-visible { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; transition: none; }
}

/* ---------- Updates / timeline ---------- */
.updates {
  background: var(--dark);
  color: #fff;
  padding: 88px 0;
}
.updates h2 { font-size: clamp(26px, 3.4vw, 36px); margin-bottom: 16px; }
.updates-sub { color: rgba(255,255,255,0.65); font-size: 16px; max-width: 60ch; margin-bottom: 48px; }

.timeline {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 36px;
  max-width: 640px;
  margin-top: 8px;
  padding-left: 34px;
}
.timeline::before {
  content: "";
  position: absolute;
  top: 6px;
  bottom: 6px;
  left: 5px;
  width: 1px;
  background: linear-gradient(
    to bottom,
    rgba(146,206,255,0),
    rgba(146,206,255,.5) 8%,
    rgba(146,206,255,.5) 92%,
    rgba(146,206,255,0)
  );
}
.timeline-item {
  position: relative;
  border: 1px solid rgba(255,255,255,0.14);
  border-radius: var(--radius);
  padding: 28px;
  transition: border-color .2s ease, transform .2s ease;
}
.timeline-item::before {
  content: "";
  position: absolute;
  top: 32px;
  left: -34px;
  width: 13px;
  height: 13px;
  border-radius: 50%;
  background: var(--blue);
  box-shadow: 0 0 0 5px rgba(146,206,255,0.16);
  transition: box-shadow .2s ease;
}
.timeline-item:hover {
  border-color: rgba(146,206,255,0.5);
  transform: translateX(4px);
}
.timeline-item:hover::before { box-shadow: 0 0 0 7px rgba(146,206,255,0.24); }

.timeline-date {
  display: inline-block;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.04em;
  color: var(--blue);
  background: rgba(146,206,255,0.12);
  padding: 5px 12px;
  border-radius: 999px;
  margin-bottom: 16px;
}
.timeline-item h3 { font-size: 20px; margin-bottom: 10px; }
.timeline-item p { color: rgba(255,255,255,0.68); font-size: 14.5px; margin: 0; }

/* ---------- Careers ---------- */
.careers { padding: 88px 0; }
.careers h2 { font-size: clamp(26px, 3.4vw, 34px); max-width: 24ch; margin-bottom: 16px; }
.careers-sub { font-size: 16px; color: var(--dark); opacity: .7; max-width: 48ch; margin-bottom: 32px; }
/* the "ch" width above is tuned for Latin text; CJK glyphs are much
   wider per character, so the same limit wraps Chinese copy early —
   let it run the full container width in Chinese so it stays on one line */
html[lang="zh-CN"] .careers-sub { max-width: none; }

.btn-large { padding: 16px 32px; font-size: 16px; display: inline-flex; align-items: center; gap: 10px; }
.btn-arrow { transition: transform .2s ease; }
.btn-large:hover .btn-arrow { transform: translateX(3px); }

/* ---------- Footer / Contact ---------- */
.site-footer {
  position: relative;
  background: var(--black);
  color: #fff;
  padding: 88px 0 40px;
  overflow: hidden;
}

.footer-flow {
  position: absolute;
  inset: 0;
  pointer-events: none;
  opacity: .5;
}
.footer-flow span {
  position: absolute;
  top: -20%;
  width: 1px;
  height: 55%;
  background: linear-gradient(to bottom, transparent, var(--blue), transparent);
  animation: flow 6s linear infinite;
}
.footer-flow span:nth-child(1) { left: 8%;  animation-delay: 0s;   opacity:.5;}
.footer-flow span:nth-child(2) { left: 20%; animation-delay: 1.2s; opacity:.3;}
.footer-flow span:nth-child(3) { left: 33%; animation-delay: 2.4s; opacity:.6;}
.footer-flow span:nth-child(4) { left: 47%; animation-delay: .6s;  opacity:.35;}
.footer-flow span:nth-child(5) { left: 60%; animation-delay: 3s;   opacity:.5;}
.footer-flow span:nth-child(6) { left: 72%; animation-delay: 1.8s; opacity:.3;}
.footer-flow span:nth-child(7) { left: 84%; animation-delay: 2.7s; opacity:.55;}
.footer-flow span:nth-child(8) { left: 93%; animation-delay: .9s;  opacity:.3;}

@keyframes flow {
  0%   { transform: translateY(-40%); opacity: 0; }
  15%  { opacity: 1; }
  85%  { opacity: 1; }
  100% { transform: translateY(220%); opacity: 0; }
}

.footer-contact {
  position: relative;
  z-index: 1;
  max-width: 620px;
}

.contact-title, .footer-contact h2 { font-size: clamp(26px, 3.2vw, 34px); margin-bottom: 14px; }
.contact-sub { color: rgba(255,255,255,0.65); font-size: 15.5px; max-width: 50ch; margin-bottom: 28px; }
html[lang="zh-CN"] .contact-sub { max-width: none; }

.contact-info { list-style: none; margin: 0; padding: 0; font-size: 15px; }
.contact-info li { margin-bottom: 8px; color: rgba(255,255,255,0.8); }
.contact-info a { text-decoration: underline; text-underline-offset: 3px; }

.contact-form { display: flex; flex-direction: column; gap: 12px; max-width: 480px; }
.contact-form input,
.contact-form textarea {
  background: rgba(255,255,255,0.06);
  border: 1px solid rgba(255,255,255,0.18);
  border-radius: 12px;
  padding: 13px 16px;
  color: #fff;
  font-family: inherit;
  font-size: 14.5px;
  resize: vertical;
}
.contact-form input::placeholder, .contact-form textarea::placeholder { color: rgba(255,255,255,0.45); }
.contact-form .btn { align-self: flex-start; margin-top: 4px; }
.contact-form .btn-primary { background: var(--blue); color: var(--black); }
.contact-form .btn-primary:hover { background: var(--blue-light); }
.form-note { font-size: 12.5px; color: rgba(255,255,255,0.4); margin: 6px 0 0; }

.footer-bottom {
  position: relative;
  z-index: 1;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 28px;
  margin-top: 64px;
  padding-top: 32px;
  border-top: 1px solid rgba(255,255,255,0.12);
}
.footer-brand { display: flex; flex-direction: column; gap: 10px; }
.footer-brand-row { display: flex; align-items: center; }
.footer-logo { height: 24px; width: auto; opacity: .9; }
.footer-tagline { font-size: 13px; color: rgba(255,255,255,0.5); margin: 0; }
.footer-links { display: flex; flex-direction: column; align-items: flex-end; gap: 10px; }
.footer-nav { display: flex; gap: 20px; font-size: 14px; }
.footer-nav a { color: rgba(255,255,255,0.7); }
.footer-nav a:hover { color: #fff; }
.footer-copy { font-size: 12.5px; color: rgba(255,255,255,0.4); margin: 0; }

/* ---------- Responsive ---------- */
@media (max-width: 860px) {
  .header-inner { gap: 12px; padding-top: 8px; padding-bottom: 8px; }
  .header-actions { gap: 8px; }
  .main-nav { display: none; }
  .nav-burger { display: flex; width: 44px; height: 44px; padding: 9px 6px; }
  .nav-mobile-only { display: block; }
  .header-contact-btn { display: none; }
  .hero-scroll-track { height: 190svh; }
  .hero-bg-pin { position: sticky; top: 61px; height: max(480px, calc(100svh - 61px)); }
  .hero-photo { height: 100%; min-height: 0; }
  .hero-bg { position: absolute; inset: 0; background: linear-gradient(rgba(19,20,21,.58), rgba(19,20,21,.72)), url("assets/hero-poster-0901.jpg") center / cover no-repeat; }
  .hero-bg video { position: relative; z-index: 1; width: 100%; height: 100%; object-fit: contain; background: transparent; }
  .hero-copy-layer { height: 90svh; min-height: 0; }
  .hero-copy h1 {
    display: block;
    max-width: 20ch;
    font-size: clamp(25px, 7.5vw, 38px);
    line-height: 1.22;
    letter-spacing: .035em;
    white-space: normal;
    text-wrap: balance;
    transform: none !important;
  }
  .values-cards { grid-template-columns: repeat(2, 1fr); }

  /* timeline switches from a horizontal connector to a vertical one on mobile */
  .timeline {
    grid-template-columns: 1fr;
    gap: 36px;
    padding-top: 0;
    padding-left: 26px;
  }
  .timeline::before {
    top: 0;
    bottom: 0;
    left: 5px;
    right: auto;
    width: 1px;
    height: auto;
    background: linear-gradient(
      to bottom,
      rgba(146,206,255,0),
      rgba(146,206,255,.5) 8%,
      rgba(146,206,255,.5) 92%,
      rgba(146,206,255,0)
    );
  }
  .timeline-item::before {
    top: 26px;
    left: -26px;
    transform: none;
  }

  .footer-bottom { flex-direction: column; align-items: flex-start; gap: 24px; }
  .footer-links { align-items: flex-start; }
}

@media (max-width: 860px) {
  .main-nav.open {
    display: flex;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background: var(--cream);
    flex-direction: column;
    padding: 16px 24px 24px;
    gap: 16px;
    border-bottom: 1px solid rgba(19,20,21,0.08);
  }
}

@media (max-width: 520px) {
  .container { padding-left: 20px; padding-right: 20px; }
  .brand-logo { height: 26px; }
  .hero-copy { padding: 0 4px; }
  .hero-tag { margin-bottom: 28px; }
  .hero-sound-toggle { right: 12px; bottom: 12px; }
}

@media (max-width: 860px), (hover: none), (pointer: coarse) {
  #robotics-four-dimensions .rv-desktop { display: none; }
  #robotics-four-dimensions .rv-mobile { display: block; padding: 18px 4px 12px; }
  #robotics-four-dimensions .rv-mobile-core { display: grid; place-items: center; height: 150px; }
  #robotics-four-dimensions .rv-mobile-core svg { width: 142px; height: 142px; overflow: visible; }
  #robotics-four-dimensions .rv-mobile-list { display: grid; gap: 8px; }
  #robotics-four-dimensions .rv-mobile-node { width: 100%; border: 0; color: inherit; font: inherit; text-align: left; display: grid; grid-template-columns: 34px 1fr; gap: 10px; align-items: center; padding: 10px 8px; background: color-mix(in srgb, var(--cream) 76%, transparent); border-radius: 12px; cursor: pointer; transition: background .5s ease, transform .5s ease; }
  #robotics-four-dimensions .rv-mobile-node strong { display: block; font-weight: 700; font-size: 14.5px; }
  #robotics-four-dimensions .rv-mobile-node span { color: var(--muted); font-size: 12px; }
  #robotics-four-dimensions .rv-mobile-node i { width: 30px; height: 30px; display: grid; place-items: center; color: var(--black); }
  #robotics-four-dimensions .rv-mobile-node:nth-child(1):hover { background: color-mix(in srgb, var(--c1) 16%, var(--cream)); transform: translateX(4px); }
  #robotics-four-dimensions .rv-mobile-node:nth-child(2):hover { background: color-mix(in srgb, var(--c2) 16%, var(--cream)); transform: translateX(4px); }
  #robotics-four-dimensions .rv-mobile-node:nth-child(3):hover { background: color-mix(in srgb, var(--c3) 16%, var(--cream)); transform: translateX(4px); }
  #robotics-four-dimensions .rv-mobile-node:nth-child(4):hover { background: color-mix(in srgb, var(--c4) 16%, var(--cream)); transform: translateX(4px); }
  #robotics-four-dimensions .rv-mobile-node[aria-pressed="true"] { background: color-mix(in srgb, var(--blue) 18%, var(--cream)); }
  #robotics-four-dimensions .rv-mobile-player { margin: 6px 0 10px; overflow: hidden; border-radius: 14px; background: var(--black); }
  #robotics-four-dimensions .rv-mobile-player[hidden] { display: none; }
  #robotics-four-dimensions .rv-mobile-player video { display: block; width: 100%; aspect-ratio: 16 / 9; object-fit: cover; }
  #robotics-four-dimensions .rv-mobile:has(.rv-mobile-node:nth-child(1):hover) .rv-tint-flood-m,
  #robotics-four-dimensions .rv-mobile:has(.rv-mobile-node:nth-child(1):hover) .rv-pulse { flood-color: var(--c1); stroke: var(--c1); }
  #robotics-four-dimensions .rv-mobile:has(.rv-mobile-node:nth-child(2):hover) .rv-tint-flood-m,
  #robotics-four-dimensions .rv-mobile:has(.rv-mobile-node:nth-child(2):hover) .rv-pulse { flood-color: var(--c2); stroke: var(--c2); }
  #robotics-four-dimensions .rv-mobile:has(.rv-mobile-node:nth-child(3):hover) .rv-tint-flood-m,
  #robotics-four-dimensions .rv-mobile:has(.rv-mobile-node:nth-child(3):hover) .rv-pulse { flood-color: var(--c3); stroke: var(--c3); }
  #robotics-four-dimensions .rv-mobile:has(.rv-mobile-node:nth-child(4):hover) .rv-tint-flood-m,
  #robotics-four-dimensions .rv-mobile:has(.rv-mobile-node:nth-child(4):hover) .rv-pulse { flood-color: var(--c4); stroke: var(--c4); }
}

@media (prefers-reduced-motion: reduce) {
  #robotics-four-dimensions *, #robotics-four-dimensions *::before, #robotics-four-dimensions *::after { animation: none !important; transition: none !important; }
  .hero-scroll-track { height: auto; min-height: max(480px, calc(100svh - 62px)); }
  .hero-bg-pin { position: absolute; inset: 0; }
  .hero-photo { height: 100%; min-height: 0; }
  .hero-bg { position: absolute; inset: 0; }
  .hero-bg video { width: 100%; height: 100%; object-fit: contain; background: transparent; }
  .hero-copy-layer { position: relative; height: max(480px, calc(100svh - 62px)); min-height: 0; padding: 0; }
  .hero-sound-toggle { display: none; }
}