:root {
  --ink: #0b1220;
  --muted: #5b6577;
  --line: rgba(15, 23, 42, 0.08);
  --soft: #f4f6f9;
  --btn: #1d4ed8;
  --shell: 1120px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}
html { scroll-behavior: smooth; }
body {
  font-family: "Instrument Sans", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
}
.shell { max-width: var(--shell); margin: 0 auto; padding: 0 24px; }

.hero {
  position: relative;
  padding: clamp(48px, 8vw, 88px) 0 0;
  text-align: center;
}
.hero::before {
  content: "";
  position: absolute;
  left: 50%;
  top: 8%;
  width: min(560px, 80vw);
  height: 220px;
  transform: translateX(-50%);
  background:
    radial-gradient(ellipse at 50% 40%, rgba(37, 99, 235, 0.16), transparent 68%),
    radial-gradient(ellipse at 70% 60%, rgba(14, 165, 233, 0.10), transparent 60%);
  pointer-events: none;
  z-index: 0;
  filter: blur(2px);
  animation: aura 6s ease-in-out infinite alternate;
}
.hero-copy {
  position: relative;
  z-index: 1;
  max-width: 42rem;
  margin: 0 auto;
  padding: 0 8px;
  animation: rise 0.8s var(--ease) both;
}
.hero h1 {
  margin: 0;
  font-size: clamp(2.15rem, 5vw, 3.55rem);
  line-height: 1.12;
  letter-spacing: -0.048em;
  font-weight: 700;
  color: var(--ink);
}
.hero h1 .brand-grad,
.hero h1 .grad {
  display: inline-block;
  background: linear-gradient(105deg, #0f172a 0%, #1d4ed8 28%, #0ea5e9 52%, #2563eb 72%, #0f172a 100%);
  background-size: 220% 100%;
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  -webkit-text-fill-color: transparent;
  animation: sheen 5.5s ease-in-out infinite;
}
.hero .lead {
  margin: 18px auto 0;
  max-width: 36rem;
  color: var(--muted);
  font-size: clamp(1rem, 1.5vw, 1.125rem);
  line-height: 1.7;
}
.hero .lead .mark {
  color: #1e40af;
  font-weight: 550;
  background: linear-gradient(180deg, transparent 62%, rgba(37, 99, 235, 0.14) 62%);
  border-radius: 2px;
  padding: 0 1px;
}
a.cta {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 48px;
  padding: 0 30px;
  border-radius: 980px;
  background: linear-gradient(135deg, #2563eb 0%, #1d4ed8 55%, #0ea5e9 140%);
  background-size: 140% 140%;
  color: #fff;
  font-weight: 600;
  font-size: 15px;
  text-decoration: none;
  box-shadow: 0 10px 28px -12px rgba(37, 99, 235, 0.55);
  transition: background-position .35s var(--ease), transform .2s var(--ease), box-shadow .2s;
}
a.cta:hover {
  color: #fff;
  background-position: 100% 50%;
  transform: translateY(-1px);
}
a.cta.ghost {
  background: #fff;
  color: var(--ink);
  border: 1px solid var(--line);
  box-shadow: none;
}
a.cta.ghost:hover { color: var(--ink); }
.hero .cta { margin-top: 28px; animation: rise 0.85s var(--ease) 0.08s both; }
.hero-visual {
  margin: clamp(40px, 6vw, 64px) auto 0;
  max-width: 960px;
  padding: 0 16px;
  animation: float-in 1s var(--ease) 0.12s both;
}
.hero-visual img { width: 100%; height: auto; display: block; background: transparent; }

.features { margin-top: clamp(48px, 8vw, 96px); border-top: 1px solid var(--line); }
.chapter {
  padding: clamp(56px, 9vw, 104px) 0;
  border-bottom: 1px solid var(--line);
}
.chapter:nth-child(even) { background: linear-gradient(180deg, var(--soft) 0%, #fff 100%); }
.chapter-grid {
  display: grid;
  gap: clamp(28px, 4vw, 56px);
  align-items: start;
}
@media (min-width: 900px) {
  .chapter-grid { grid-template-columns: minmax(0, 1.05fr) minmax(0, 0.95fr); gap: 64px; }
  .chapter.reverse .chapter-grid { grid-template-columns: minmax(0, 0.95fr) minmax(0, 1.05fr); }
  .chapter.reverse .media { order: 2; }
  .chapter.reverse .copy { order: 1; }
  .media { position: sticky; top: 88px; }
}
.media {
  position: relative;
  aspect-ratio: 4 / 3;
  border-radius: 20px;
  overflow: hidden;
  background: radial-gradient(ellipse at 50% 45%, #1a2744 0%, #0b1220 68%, #070b14 100%);
  box-shadow: inset 0 0 0 1px rgba(148, 163, 184, 0.08);
}
.media img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
  padding: 12px;
}
.chapter .copy { max-width: 38rem; }
@media (min-width: 900px) {
  .chapter:not(.reverse) .copy { padding-right: 4px; max-width: none; }
  .chapter.reverse .copy { padding-left: 4px; max-width: none; }
}
.no {
  display: inline-block;
  font-size: 12px;
  font-weight: 650;
  letter-spacing: 0.16em;
  color: #94a3b8;
  margin-bottom: 14px;
}
.chapter h2 {
  margin: 0;
  font-size: clamp(1.45rem, 2.4vw, 1.9rem);
  line-height: 1.25;
  letter-spacing: -0.035em;
  font-weight: 700;
  color: var(--ink);
}
.chapter .body {
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 1.02rem;
  line-height: 1.8;
}
.points { margin: 20px 0 0; padding: 0; list-style: none; display: grid; gap: 12px; }
.points li {
  position: relative;
  padding-left: 18px;
  font-size: 0.95rem;
  line-height: 1.7;
  color: #3f4b5f;
}
.points li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.65em;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: #94a3b8;
}
.foot-cta {
  text-align: center;
  padding: clamp(72px, 12vw, 120px) 24px;
  background: radial-gradient(700px 280px at 50% 0%, #e8eef8 0%, transparent 70%);
}
.foot-cta h2 {
  margin: 0;
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  letter-spacing: -0.04em;
  font-weight: 700;
  color: var(--ink);
}
.foot-cta p { margin: 12px auto 28px; max-width: 28rem; color: var(--muted); font-size: 1.02rem; line-height: 1.65; }

/* Download */
.dl-hero { padding: clamp(48px, 8vw, 80px) 0 20px; }
.os-row { display: flex; flex-wrap: wrap; justify-content: center; gap: 10px; margin: 32px 0 0; }
.os-chip {
  appearance: none; border: 1px solid var(--line); background: #fff; color: var(--ink);
  display: inline-flex; align-items: center; height: 42px; padding: 0 16px;
  border-radius: 999px; font-size: 14px; font-weight: 600; cursor: pointer;
  font-family: inherit;
}
.os-chip:hover { border-color: #93c5fd; color: var(--btn); }
.os-chip[aria-selected="true"] {
  background: var(--ink); color: #fff; border-color: var(--ink);
}
.stage { margin: 36px 0 8px; overflow: hidden; border-top: 1px solid var(--line); }
.track { display: flex; width: 500%; transition: transform .55s var(--ease); }
.plat {
  width: 20%;
  flex: 0 0 20%;
  display: grid;
  gap: 28px;
  align-items: start;
  padding: 40px 2px 8px;
}
@media (min-width: 860px) {
  .plat { grid-template-columns: 1.05fr 0.95fr; gap: 48px; }
}
.shot {
  border-radius: 18px;
  overflow: hidden;
  background: var(--soft);
  aspect-ratio: 16 / 10;
}
.shot img { width: 100%; height: 100%; object-fit: cover; display: block; }
.plat h2 { margin: 0 0 10px; font-size: 1.45rem; letter-spacing: -0.03em; text-align: center; color: var(--ink); }
.plat p { margin: 0; color: var(--muted); line-height: 1.75; }
.actions { display: flex; flex-wrap: wrap; justify-content: center; gap: 10px; margin: 16px 0 8px; }
.actions .cta { height: 46px; padding: 0 22px; font-size: 14px; }
.sys { margin: 0 0 6px; font-size: 13px; color: #8b95a5; text-align: center; }
.sys + .body { margin-top: 12px; }
.plat .body { margin: 0 0 12px; font-size: 0.98rem; }
.facts { margin: 16px 0 0; padding: 0; list-style: none; display: grid; gap: 12px; }
.facts li { color: #3f4b5f; font-size: 0.92rem; line-height: 1.6; }
.facts strong { display: block; color: var(--ink); font-size: 0.95rem; margin-bottom: 2px; }
.plat[aria-hidden="true"] { pointer-events: none; }
.faq { padding: 56px 0 88px; border-top: 1px solid var(--line); }
.faq-head { text-align: center; margin: 0 auto 28px; max-width: 36rem; }
.faq-head h2 { margin: 0; font-size: clamp(1.45rem, 2.6vw, 1.85rem); letter-spacing: -0.03em; color: var(--ink); }
.faq-head p { margin: 12px 0 0; color: var(--muted); line-height: 1.7; }
.faq-list { max-width: 40rem; margin: 0 auto; }
.faq-list details { border-bottom: 1px solid var(--line); padding: 16px 0; }
.faq-list summary { cursor: pointer; font-weight: 650; font-size: 1rem; list-style: none; color: var(--ink); }
.faq-list summary::-webkit-details-marker { display: none; }
.faq-list details p { margin: 10px 0 0; color: var(--muted); line-height: 1.75; font-size: 0.95rem; }

@keyframes rise {
  from { opacity: 0; transform: translateY(14px); }
  to { opacity: 1; transform: translateY(0); }
}
@keyframes float-in {
  from { opacity: 0; transform: translateY(28px) scale(0.985); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}
@keyframes sheen {
  0%, 100% { background-position: 0% 50%; }
  50% { background-position: 100% 50%; }
}
@keyframes aura {
  from { opacity: 0.75; transform: translateX(-50%) scale(1); }
  to { opacity: 1; transform: translateX(-50%) scale(1.06); }
}
@media (prefers-reduced-motion: reduce) {
  .hero::before, .hero-copy, .hero .cta, .hero-visual, .hero h1 .brand-grad, .hero h1 .grad { animation: none; }
  .track { transition: none; }
}