/* ==========================================================================
   北宸数智 v3 · Apple 风格单页官网
   设计语言：三段式深浅节奏 / 大留白 / 精确排版 / 滚动叙事
   ========================================================================== */

/* ---------- 设计令牌 ---------- */
:root {
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --nav-h: 64px;
  --maxw: 1280px;
  --teal: #7af6e2;
}

/* 流式根字号：笔记本 ~16px，2K 屏 ~19px，正文随视口平滑放大 */
html { font-size: clamp(16px, 0.3vw + 11.5px, 19.5px); }

html[data-theme="dark"] {
  --bg: #05080f;
  --bg-2: #0a101c;
  --fg: #f2f5f9;
  --fg-dim: rgba(242, 245, 249, 0.56);
  --fg-faint: rgba(242, 245, 249, 0.32);
  --hair: rgba(242, 245, 249, 0.12);
  --card: rgba(255, 255, 255, 0.04);
  --card-hover: rgba(255, 255, 255, 0.07);
  --glass: rgba(5, 8, 15, 0.55);
  --accent: #7af6e2;
  --accent-ink: #04110d;
  --shade-a: rgba(5, 8, 15, 0.55);
}

html[data-theme="light"] {
  --bg: #f4f5f7;
  --bg-2: #ffffff;
  --fg: #14181f;
  --fg-dim: rgba(20, 24, 31, 0.62);
  --fg-faint: rgba(20, 24, 31, 0.34);
  --hair: rgba(20, 24, 31, 0.12);
  --card: #ffffff;
  --card-hover: #ffffff;
  --glass: rgba(244, 245, 247, 0.72);
  --accent: #0a8a74;
  --accent-ink: #ffffff;
  --shade-a: rgba(244, 245, 247, 0.55);
}

/* ---------- 基础 ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { -webkit-text-size-adjust: 100%; scroll-behavior: auto; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text",
    "Helvetica Neue", "PingFang SC", "HarmonyOS Sans SC", "MiSans", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.75;
  font-size: 1.05rem;
  overflow-x: clip;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; cursor: pointer; }
::selection { background: var(--accent); color: var(--accent-ink); }

::-webkit-scrollbar { width: 10px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--hair); border-radius: 5px; }

:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 4px; }

.skip {
  position: fixed; top: -60px; left: 16px; z-index: 300;
  background: var(--fg); color: var(--bg);
  padding: 10px 18px; border-radius: 999px; font-size: 0.9rem;
  transition: top 0.3s var(--ease);
}
.skip:focus { top: 12px; }

/* 细颗粒噪点，增加胶片质感 */
body::after {
  content: ""; position: fixed; inset: 0; z-index: 250; pointer-events: none;
  opacity: 0.05;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='160' height='160'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='2'/%3E%3C/filter%3E%3Crect width='160' height='160' filter='url(%23n)' opacity='0.5'/%3E%3C/svg%3E");
}

.container { width: min(var(--maxw), 100% - 12vw); margin-inline: auto; }

/* ---------- 通用排版元素 ---------- */
.eyebrow {
  display: inline-flex; align-items: center; gap: 12px;
  font-size: 0.78rem; font-weight: 600; letter-spacing: 0.22em; text-transform: uppercase;
  color: var(--accent);
}
.eyebrow::before { content: ""; width: 28px; height: 1px; background: var(--accent); opacity: 0.8; }

h1, h2, h3 { font-weight: 700; line-height: 1.14; letter-spacing: 0.005em; }

.act-head h2 { font-size: clamp(36px, 4.2vw + 6px, 80px); margin: 22px 0 20px; }
.act-desc { max-width: 580px; color: var(--fg-dim); font-size: 1.08rem; }

.section { padding: clamp(96px, 16vh, 180px) 0; position: relative; }

/* 文字链接 / 按钮 */
.cta {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 15px 30px; border-radius: 999px;
  background: var(--fg); color: var(--bg);
  font-size: 1rem; font-weight: 600; letter-spacing: 0.02em;
  transition: transform 0.45s var(--ease), opacity 0.3s;
  will-change: transform;
}
.cta:hover { transform: translateY(-2px) scale(1.02); }
.cta:active { transform: scale(0.98); }
.cta svg { width: 17px; height: 17px; }

.text-link {
  display: inline-flex; align-items: center; gap: 8px;
  color: var(--accent); font-size: 1.05rem; font-weight: 600;
  border-bottom: 1px solid transparent; transition: border-color 0.3s;
}
.text-link:hover { border-color: var(--accent); }

/* ---------- 导航 ---------- */
.nav {
  position: fixed; inset: 0 0 auto 0; z-index: 200;
  height: var(--nav-h);
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 max(4vw, 20px);
  background: transparent;
  border-bottom: 1px solid transparent;
}
.nav.scrolled {
  background: var(--glass);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  backdrop-filter: saturate(180%) blur(20px);
  border-bottom-color: var(--hair);
}

.brand { display: inline-flex; align-items: baseline; gap: 10px; z-index: 2; }
.brand-mark { color: var(--accent); font-size: 1.15rem; line-height: 1; }
.brand b { font-size: 1.02rem; letter-spacing: 0.04em; }
.brand small { font-size: 0.66rem; letter-spacing: 0.3em; color: var(--fg-faint); margin-left: 2px; }

.nav-links { display: flex; align-items: center; gap: 6px; }
.nav-links a {
  font-size: 0.88rem; color: var(--fg-dim); padding: 8px 14px; border-radius: 999px;
  transition: color 0.3s, background-color 0.3s;
}
.nav-links a:hover { color: var(--fg); background: var(--card); }
.nav-links a.nav-cta { color: var(--accent-ink); background: var(--accent); font-weight: 600; margin-left: 10px; }
.nav-links a.nav-cta:hover { opacity: 0.88; background: var(--accent); }

.menu-toggle { display: none; z-index: 2; width: 42px; height: 42px; position: relative; }
.menu-toggle span {
  position: absolute; left: 10px; right: 10px; height: 1.6px; background: var(--fg);
  transition: transform 0.4s var(--ease), top 0.4s var(--ease);
}
.menu-toggle span:nth-child(1) { top: 17px; }
.menu-toggle span:nth-child(2) { top: 25px; }
body.menu-open .menu-toggle span:nth-child(1) { top: 21px; transform: rotate(45deg); }
body.menu-open .menu-toggle span:nth-child(2) { top: 21px; transform: rotate(-45deg); }

.mobile-menu {
  position: fixed; inset: 0; z-index: 199;
  display: flex; flex-direction: column; justify-content: center; gap: 6px;
  padding: 0 10vw;
  background: var(--glass);
  -webkit-backdrop-filter: saturate(180%) blur(30px);
  backdrop-filter: saturate(180%) blur(30px);
  opacity: 0; visibility: hidden; transition: opacity 0.45s var(--ease), visibility 0.45s;
}
body.menu-open .mobile-menu { opacity: 1; visibility: visible; }
.mobile-menu a { font-size: 1.6rem; font-weight: 700; padding: 12px 0; border-bottom: 1px solid var(--hair); }

/* ---------- 幕一 · Hero（深色） ---------- */
.hero {
  position: relative; min-height: 100vh; min-height: 100svh;
  display: grid; place-items: center; overflow: clip;
}
.hero-media, .hero-media img { position: absolute; inset: 0; width: 100%; height: 100%; }
.hero-media img { object-fit: cover; }
.hero-shade {
  position: absolute; inset: 0; z-index: 1;
  background:
    radial-gradient(120% 90% at 50% 10%, transparent 40%, rgba(5, 8, 15, 0.5) 100%),
    linear-gradient(180deg, rgba(5, 8, 15, 0.42) 0%, rgba(5, 8, 15, 0.08) 42%, rgba(5, 8, 15, 0.55) 78%, #05080f 100%);
}
#particles { position: absolute; inset: 0; z-index: 2; }

.hero-content { position: relative; z-index: 3; text-align: center; padding: 0 6vw; color: #f5f8fb; }
.hero .eyebrow { color: #9df2e2; }
.hero .eyebrow::before { background: #9df2e2; }

.hero h1 {
  font-size: clamp(52px, 8.6vw, 128px);
  margin: 30px 0 26px; color: #fbfdff;
}
.hero h1 .line { display: block; overflow: hidden; padding-block: 0.06em; }
.hero h1 .line-in { display: inline-block; will-change: transform; }
.hero h1 .dot { color: var(--teal); }

.hero-sub {
  color: rgba(245, 248, 251, 0.78); font-size: 1.12rem;
  margin-bottom: 44px;
}

.hero-meta {
  position: absolute; z-index: 3; left: max(4vw, 20px); bottom: 34px;
  display: flex; align-items: center; gap: 12px;
  font-size: 0.68rem; letter-spacing: 0.28em; color: rgba(245, 248, 251, 0.5);
  text-transform: uppercase;
}
.hero-meta i { width: 46px; height: 1px; background: rgba(245, 248, 251, 0.3); }

.scroll-hint {
  position: absolute; z-index: 3; bottom: 34px; left: 50%; transform: translateX(-50%);
  font-size: 0.78rem; letter-spacing: 0.2em; color: rgba(245, 248, 251, 0.6);
  animation: hint-float 2.6s var(--ease) infinite;
}
@keyframes hint-float { 0%, 100% { transform: translate(-50%, 0); } 50% { transform: translate(-50%, 8px); } }

/* ---------- 幕二 · 信念（深色，云海图为框中亮色） ---------- */
.belief-inner { max-width: 900px; margin-inline: auto; text-align: center; padding-top: 14vh; }
.belief .eyebrow { margin-bottom: 40px; }

.manifesto {
  font-size: clamp(28px, 3.6vw + 8px, 68px);
  font-weight: 700; line-height: 1.62; letter-spacing: 0.01em;
  text-wrap: balance;
}
.manifesto .ch { display: inline-block; opacity: 0.13; will-change: opacity; }

.belief-sign {
  margin-top: 52px; font-size: 0.82rem; letter-spacing: 0.24em;
  color: var(--fg-faint); text-transform: uppercase;
}

.belief-media { margin-top: clamp(80px, 12vh, 140px); }

/* ---------- 通用媒体（视差容器） ---------- */
.media { position: relative; overflow: hidden; border-radius: 26px; isolation: isolate; }
.media img { width: 100%; height: 100%; object-fit: cover; will-change: transform; }
.media svg.art { display: block; width: 100%; height: 100%; }

.belief-media { aspect-ratio: 21 / 9; }
.belief-media img { height: 118%; }

/* ---------- SVG 艺术图形 · 云端之城 ---------- */
.cc-clouds { animation: cc-drift 44s ease-in-out infinite alternate; }
.cc-clouds.cc-b { animation-duration: 34s; animation-direction: alternate-reverse; }
@keyframes cc-drift { from { transform: translateX(-46px); } to { transform: translateX(58px); } }
.cc-sun circle { animation: cc-sun 8s ease-in-out infinite; }
@keyframes cc-sun { 0%, 100% { opacity: 0.82; } 50% { opacity: 1; } }
.cc-drone { animation: cc-float 5.5s ease-in-out infinite; }
@keyframes cc-float { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-16px); } }
.cc-star { animation: cc-twinkle 4.5s ease-in-out infinite; }
.cc-star:nth-child(2n) { animation-delay: -1.6s; }
.cc-star:nth-child(3n) { animation-delay: -2.8s; }
@keyframes cc-twinkle { 0%, 100% { opacity: 0.35; } 50% { opacity: 1; } }
.cc-win { animation: cc-win 7s ease-in-out infinite; }
.cc-win:nth-child(2n) { animation-delay: -2.5s; }
.cc-win:nth-child(3n) { animation-delay: -4.6s; }
@keyframes cc-win { 0%, 100% { opacity: 0.7; } 50% { opacity: 1; } }

/* ---------- SVG 艺术图形 · 数据城市 ---------- */
.dc-line { stroke-dasharray: 7 11; animation: dc-dash 1.5s linear infinite; }
@keyframes dc-dash { to { stroke-dashoffset: -72; } }
.dc-ring { transform-origin: center; transform-box: fill-box; animation: dc-ring 2.8s ease-out infinite; }
.dc-ring:nth-of-type(2) { animation-delay: 0.9s; }
@keyframes dc-ring { 0% { transform: scale(0.45); opacity: 0.85; } 75% { transform: scale(2.1); opacity: 0; } 100% { opacity: 0; } }

/* ---------- SVG 艺术图形 · 业务星图 ---------- */
.ct-line { stroke-dasharray: 4 9; animation: ct-dash 2.4s linear infinite; }
@keyframes ct-dash { to { stroke-dashoffset: -52; } }
.ct-core { animation: ct-core 4.5s ease-in-out infinite; transform-origin: center; transform-box: fill-box; }
@keyframes ct-core { 0%, 100% { transform: scale(1); opacity: 0.9; } 50% { transform: scale(1.12); opacity: 1; } }
.ct-node { animation: ct-bob 7s ease-in-out infinite; }
.ct-node:nth-of-type(2n) { animation-delay: -2.4s; }
.ct-node:nth-of-type(3n) { animation-delay: -4.2s; }
@keyframes ct-bob { 0%, 100% { translate: 0 0; } 50% { translate: 0 -12px; } }

/* SVG 内文本 */
.art text { font-family: inherit; }

/* ---------- 幕三 · 低空经济（浅色） ---------- */
.act-head { padding: clamp(80px, 12vh, 130px) 0 0; }
.act-head .act-desc { margin-bottom: 0; }

.story { display: grid; grid-template-columns: 1fr 1fr; gap: clamp(40px, 6vw, 96px); align-items: start; }
.story-visual {
  position: sticky; top: calc(var(--nav-h) + 6vh);
  height: 76vh; overflow: hidden; border-radius: 26px;
}
.story-visual img { width: 145%; max-width: none; margin-left: -22.5%; height: 100%; object-fit: cover; will-change: transform; }
.story-badge {
  position: absolute; left: 22px; bottom: 20px; z-index: 2;
  display: flex; align-items: baseline; gap: 4px;
  font-family: "SF Mono", ui-monospace, "Cascadia Mono", Consolas, monospace;
  color: #eafcf7; font-size: 0.95rem;
  text-shadow: 0 1px 12px rgba(0, 0, 0, 0.6);
}
.story-badge em { font-style: normal; opacity: 0.55; font-size: 0.78rem; }
.story-badge #story-index { font-size: 1.35rem; font-weight: 700; color: #7af6e2; }
.story-tag {
  position: absolute; right: 22px; top: 20px; z-index: 2;
  font-size: 0.68rem; letter-spacing: 0.26em; color: rgba(234, 252, 247, 0.85);
  text-transform: uppercase; text-shadow: 0 1px 10px rgba(0, 0, 0, 0.6);
}

.story-steps { position: relative; padding-block: 8vh; padding-left: clamp(22px, 3vw, 44px); }
.story-progress {
  position: absolute; top: 0; bottom: 0; left: -2px; width: 1px;
  background: var(--hair);
}
.story-progress i {
  position: absolute; inset: 0; display: block; background: var(--accent);
  transform-origin: top; transform: scaleY(0); will-change: transform;
}
.step {
  min-height: 72vh; display: flex; flex-direction: column; justify-content: center;
  opacity: 0.22; transform: translateY(26px);
  transition: opacity 0.65s var(--ease), transform 0.65s var(--ease);
}
.step.active { opacity: 1; transform: none; }
.step .kicker {
  font-size: 0.72rem; letter-spacing: 0.26em; text-transform: uppercase;
  color: var(--accent); margin-bottom: 16px;
}
.step h3 { font-size: clamp(32px, 2.9vw + 6px, 60px); margin-bottom: 18px; }
.step p { max-width: 420px; color: var(--fg-dim); font-size: 1rem; }

/* 特性卡 */
.chips { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; margin-top: clamp(60px, 10vh, 110px); }
.chip {
  border: 1px solid var(--hair); border-radius: 22px; background: var(--card);
  padding: 32px 28px;
  transition: transform 0.5s var(--ease), background-color 0.4s;
}
.chip:hover { transform: translateY(-5px); background: var(--card-hover); }
.chip .no {
  font-family: "SF Mono", ui-monospace, Consolas, monospace;
  font-size: 0.76rem; color: var(--accent); letter-spacing: 0.2em;
}
.chip h3 { font-size: clamp(22px, 1vw + 10px, 32px); margin: 14px 0 10px; }
.chip p { color: var(--fg-dim); font-size: 0.96rem; }

/* 流程 */
.workflow {
  display: flex; flex-wrap: wrap; align-items: center; justify-content: center; gap: 8px 18px;
  margin-top: clamp(50px, 8vh, 90px); padding: 30px 34px;
  border: 1px solid var(--hair); border-radius: 999px; width: fit-content;
  margin-inline: auto; background: var(--card);
}
.workflow span { font-size: 0.98rem; font-weight: 600; white-space: nowrap; }
.workflow i { color: var(--accent); font-style: normal; }

/* 数据带（融入深色长幕，不再单独成块） */
.stat-band {
  text-align: center;
  margin-top: clamp(70px, 11vh, 120px);
  padding: clamp(80px, 13vh, 150px) 6vw;
}
.stat-band .eyebrow { color: var(--accent); }
.stat-band .eyebrow::before { background: var(--accent); }
.stat-band .big {
  font-size: clamp(84px, 15vw, 220px); font-weight: 800; line-height: 1;
  letter-spacing: -0.02em; font-variant-numeric: tabular-nums;
  background: linear-gradient(92deg, #7af6e2 0%, #4fd0ff 60%, #8fb7ff 100%);
  -webkit-background-clip: text; background-clip: text; color: transparent;
  background-size: 200% auto;
}
.stat-band > p { color: var(--fg-dim); margin-top: 18px; font-size: 1.05rem; }
.models { display: flex; flex-wrap: wrap; gap: 10px; justify-content: center; margin-top: 34px; }
.models span {
  font-size: 0.85rem; padding: 9px 20px; border-radius: 999px;
  border: 1px solid var(--hair); color: var(--fg-dim);
}

/* ---------- 幕四 · 智慧城运（浅色） ---------- */
.ops-media { aspect-ratio: 21 / 9; margin-top: clamp(56px, 9vh, 100px); }
.ops-media img { height: 118%; }

.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; margin-top: clamp(60px, 10vh, 110px); }
.card {
  border: 1px solid var(--hair); border-radius: 24px; background: var(--card);
  padding: 36px 30px; overflow: hidden; position: relative;
  transition: transform 0.5s var(--ease), box-shadow 0.5s var(--ease);
}
.card:hover { transform: translateY(-6px); box-shadow: 0 24px 60px -30px rgba(20, 24, 31, 0.25); }
.card .no {
  font-family: "SF Mono", ui-monospace, Consolas, monospace;
  color: var(--accent); font-size: 0.76rem; letter-spacing: 0.2em;
}
.card h3 { font-size: clamp(24px, 1vw + 12px, 34px); margin: 16px 0 6px; }
.card .card-sub { color: var(--fg-dim); font-size: 0.96rem; margin-bottom: 16px; }
.card p.desc { color: var(--fg-dim); font-size: 0.96rem; }
.card ul { list-style: none; margin-top: 20px; display: flex; flex-wrap: wrap; gap: 8px; }
.card ul li {
  font-size: 0.84rem; padding: 7px 14px; border-radius: 999px;
  border: 1px solid var(--hair); color: var(--fg);
}

.flow-band { text-align: center; padding-top: clamp(80px, 14vh, 150px); }
.flow-band h3 { font-size: clamp(26px, 2.6vw + 6px, 52px); margin-bottom: 34px; }
.flow {
  display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: 12px 22px;
}
.flow b {
  display: grid; place-items: center; width: 150px; height: 150px; border-radius: 50%;
  border: 1px solid var(--hair); background: var(--card);
  font-size: 1.15rem; font-weight: 700; position: relative;
}
.flow b small { position: absolute; top: 22px; font-family: "SF Mono", ui-monospace, Consolas, monospace; font-size: 0.66rem; letter-spacing: 0.2em; color: var(--accent); }
.flow i { color: var(--accent); font-style: normal; font-size: 1.25rem; }

/* ---------- 幕五 · 关于北宸（深色） ---------- */
.about-grid { display: grid; grid-template-columns: 1.05fr 0.95fr; gap: clamp(40px, 6vw, 90px); align-items: center; }
.about-media { aspect-ratio: 4 / 3.4; }
.about-media img { height: 116%; }
.about-copy h3 { font-size: clamp(26px, 2vw + 6px, 42px); line-height: 1.4; margin-bottom: 26px; }
.about-copy p { color: var(--fg-dim); font-size: 1rem; margin-bottom: 18px; }

.stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin-top: 44px; padding-top: 34px; border-top: 1px solid var(--hair); }
.stats strong {
  display: block; font-size: clamp(34px, 2.8vw + 6px, 60px); font-weight: 800; line-height: 1.1;
  font-variant-numeric: tabular-nums; letter-spacing: -0.01em;
}
.stats strong span { font-size: 0.42em; font-weight: 600; color: var(--fg-dim); margin-left: 4px; }
.stats p { color: var(--fg-faint); font-size: 0.84rem; margin-top: 6px; letter-spacing: 0.06em; }

.quals { margin-top: clamp(70px, 11vh, 120px); }
.quals-head { display: flex; align-items: baseline; justify-content: space-between; gap: 20px; flex-wrap: wrap; margin-bottom: 34px; }
.quals-head h3 { font-size: clamp(24px, 1.6vw + 8px, 38px); }
.quals-head p { color: var(--fg-dim); font-size: 0.96rem; }
.qual-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; }
.qual {
  display: flex; align-items: center; gap: 14px;
  border: 1px solid var(--hair); border-radius: 16px; background: var(--card);
  padding: 18px 20px; font-size: 0.92rem;
  transition: border-color 0.4s, background-color 0.4s;
}
.qual:hover { border-color: var(--accent); }
.qual svg { width: 20px; height: 20px; color: var(--accent); flex-shrink: 0; }
.qual small { margin-left: auto; color: var(--fg-faint); font-family: "SF Mono", ui-monospace, Consolas, monospace; font-size: 0.7rem; }

/* ---------- 幕六 · 联系（深色收尾） ---------- */
.contact { text-align: center; padding-bottom: clamp(110px, 16vh, 170px); }
.contact h2 { font-size: clamp(38px, 4.6vw + 6px, 84px); margin: 24px 0 22px; }
.contact .lead { max-width: 580px; margin: 0 auto 44px; color: var(--fg-dim); font-size: 1.1rem; }
.contact .cta-row { display: flex; gap: 16px; justify-content: center; flex-wrap: wrap; }
.cta.ghost { background: transparent; color: var(--fg); border: 1px solid var(--hair); }

/* ---------- 页脚 ---------- */
.footer {
  position: relative;
  min-height: 58vh;
  display: flex; flex-direction: column; justify-content: space-between; gap: 40px;
  padding: 76px max(4vw, 20px) 44px;
  border-top: 1px solid var(--hair);
  font-size: 0.84rem; color: var(--fg-faint);
}
.footer-top { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 22px; }
.footer .brand { align-items: center; }
.footer .tagline { color: var(--fg-dim); }
.footer-bottom { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 16px; }
.footer .legal { display: flex; flex-wrap: wrap; gap: 8px 22px; }
  .footer .legal a { color: inherit; }
.back-top {
  display: inline-flex; gap: 8px; align-items: center;
  color: var(--fg-dim); font-size: 0.84rem; transition: color 0.3s;
}
.back-top:hover { color: var(--fg); }

/* ---------- 子区块标题（通用） ---------- */
.sub-head { margin-bottom: clamp(30px, 4.5vh, 48px); }
.sub-head .eyebrow { margin-bottom: 16px; }
.sub-head h3 { font-size: clamp(28px, 2.4vw + 6px, 52px); line-height: 1.3; }

/* ---------- 安保演进 · 垂直时间线（浅色） ---------- */
.evolve { margin-top: clamp(70px, 11vh, 120px); }
.evolve-track {
  --pad-x: clamp(30px, 4vw, 56px);
  position: relative; display: grid; gap: clamp(44px, 7vh, 84px);
  padding-left: var(--pad-x);
}
.evolve-line { position: absolute; left: 0; top: 10px; bottom: 10px; width: 1px; background: var(--hair); }
.evolve-line i {
  position: absolute; inset: 0; display: block; background: var(--accent);
  transform-origin: top; transform: scaleY(0); will-change: transform;
}
.evolve-node {
  position: relative;
  opacity: 0.24; transform: translateY(22px);
  transition: opacity 0.65s var(--ease), transform 0.65s var(--ease);
}
.evolve-node.active { opacity: 1; transform: none; }
.evolve-year {
  position: absolute; left: calc(var(--pad-x) * -1); top: 2px;
  transform: translateX(-50%);
  font-family: "SF Mono", ui-monospace, Consolas, monospace;
  font-size: 0.82rem; letter-spacing: 0.08em; color: var(--accent);
  background: var(--bg); padding: 6px 10px; border-radius: 999px;
  border: 1px solid var(--hair); white-space: nowrap;
}
.evolve-card {
  border: 1px solid var(--hair); border-radius: 22px; background: var(--card);
  padding: 20px; max-width: 860px;
  display: grid; grid-template-columns: 300px 1fr; gap: 26px; align-items: center;
}
.evolve-img {
  border-radius: 14px; overflow: hidden; aspect-ratio: 4 / 3;
  background: var(--hair);
}
.evolve-img img { width: 100%; height: 100%; object-fit: cover; display: block; }
.evolve-body .kicker {
  font-size: 0.72rem; letter-spacing: 0.24em; text-transform: uppercase;
  color: var(--accent); margin-bottom: 10px; display: block;
}
.evolve-body h4 { font-size: clamp(20px, 1vw + 12px, 30px); margin-bottom: 8px; }
.evolve-body p { color: var(--fg-dim); font-size: 0.96rem; }

/* ---------- 八大政务巡检领域（浅色） ---------- */
.field-block { margin-top: clamp(80px, 13vh, 140px); }
.field-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.field {
  border: 1px solid var(--hair); border-radius: 20px; background: var(--card);
  padding: 28px 24px;
  transition: transform 0.5s var(--ease), background-color 0.4s;
}
.field:hover { transform: translateY(-5px); background: var(--card-hover); }
.field strong {
  display: block; font-size: clamp(38px, 2.6vw + 6px, 56px); font-weight: 800;
  line-height: 1; letter-spacing: -0.01em; color: var(--accent);
  font-variant-numeric: tabular-nums; margin-bottom: 14px;
}
.field strong.field-word { color: var(--fg); }
.field strong small { font-size: 0.4em; font-weight: 600; margin-left: 2px; }
.field h4 { font-size: 1.08rem; margin-bottom: 8px; }
.field p { color: var(--fg-dim); font-size: 0.9rem; line-height: 1.66; }

/* ---------- 幕四 · 数据价值（深色） ---------- */
.dv-lead {
  max-width: 760px; margin-top: 22px; color: var(--fg-dim); font-size: 1.12rem;
}
.dv-stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; margin-top: clamp(50px, 8vh, 90px); }
.dv-stat {
  border: 1px solid var(--hair); border-radius: 22px; background: var(--card);
  padding: 30px 26px; position: relative;
  transition: transform 0.5s var(--ease), background-color 0.4s;
}
.dv-stat:hover { transform: translateY(-5px); background: var(--card-hover); }
.dv-stat em {
  position: absolute; top: 26px; right: 22px; font-style: normal;
  font-size: 0.66rem; letter-spacing: 0.2em; color: var(--fg-faint);
  border: 1px solid var(--hair); border-radius: 999px; padding: 4px 10px;
}
.dv-stat strong {
  display: block; font-size: clamp(28px, 2vw + 8px, 44px); font-weight: 800;
  line-height: 1.15; letter-spacing: -0.01em; color: var(--accent);
  font-variant-numeric: tabular-nums; margin-bottom: 10px;
}
.dv-stat strong small { font-size: 0.42em; font-weight: 600; color: var(--fg-dim); margin-left: 3px; }
.dv-stat h4 { font-size: 1.05rem; margin-bottom: 8px; }
.dv-stat p { color: var(--fg-dim); font-size: 0.88rem; line-height: 1.66; }

/* ---------- 一键指挥系统（浅色） ---------- */
.command { margin-top: clamp(80px, 13vh, 150px); }
.command-grid { display: grid; grid-template-columns: 0.92fr 1.08fr; gap: clamp(30px, 4vw, 64px); align-items: start; }
.command-funcs { display: grid; gap: 4px; }
.cmd {
  display: grid; grid-template-columns: auto 1fr; gap: 4px 18px;
  padding: 18px 4px; border-bottom: 1px solid var(--hair);
  transition: transform 0.4s var(--ease);
}
.cmd:last-child { border-bottom: 0; }
.cmd:hover { transform: translateX(6px); }
.cmd b {
  grid-row: span 2; font-family: "SF Mono", ui-monospace, Consolas, monospace;
  color: var(--accent); font-size: 0.85rem; padding-top: 6px;
}
.cmd h4 { font-size: 1.12rem; margin-bottom: 4px; }
.cmd p { color: var(--fg-dim); font-size: 0.92rem; line-height: 1.66; }
.command-figure {
  border: 1px solid var(--hair); border-radius: 26px; background: #ffffff;
  padding: 18px; overflow: hidden;
  box-shadow: 0 30px 70px -40px rgba(20, 24, 31, 0.28);
}
.command-figure img { width: 100%; display: block; border-radius: 14px; }
.command-figure figcaption {
  display: flex; align-items: baseline; gap: 12px; padding: 16px 8px 6px;
  color: var(--fg-dim); font-size: 0.88rem;
}
.command-figure figcaption span {
  font-family: "SF Mono", ui-monospace, Consolas, monospace;
  font-size: 0.64rem; letter-spacing: 0.22em; color: var(--accent);
}

/* ---------- 六大空间信息能力（浅色） ---------- */
.geo-block { margin-top: clamp(80px, 13vh, 150px); }
.geo-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.geo {
  border: 1px solid var(--hair); border-radius: 20px; background: var(--card);
  padding: 26px 24px; transition: transform 0.5s var(--ease), background-color 0.4s;
}
.geo:hover { transform: translateY(-5px); background: var(--card-hover); }
.geo b {
  font-family: "SF Mono", ui-monospace, Consolas, monospace;
  color: var(--accent); font-size: 0.78rem; letter-spacing: 0.2em;
  display: block; margin-bottom: 14px;
}
.geo h4 { font-size: 1.1rem; margin-bottom: 8px; }
.geo p { color: var(--fg-dim); font-size: 0.9rem; line-height: 1.66; }

/* ---------- 幕六 · 实战足迹（浅色） ---------- */
.cases-lead { max-width: 680px; margin-top: 22px; color: var(--fg-dim); font-size: 1.1rem; }
.cases-scroll { position: relative; }
.case-track-wrap {
  position: sticky; top: calc(var(--nav-h) + 5vh);
  overflow: hidden; padding-block: 5vh;
}
.case-track { display: flex; gap: 20px; padding-inline: max(4vw, 20px); will-change: transform; }
.case {
  flex: 0 0 auto; width: clamp(290px, 34vw, 420px);
  border: 1px solid var(--hair); border-radius: 22px; background: var(--card);
  padding: 30px 28px; display: flex; flex-direction: column; min-height: 218px;
  transition: transform 0.5s var(--ease), border-color 0.4s;
}
.case:hover { transform: translateY(-6px); border-color: var(--accent); }
.case-date {
  font-family: "SF Mono", ui-monospace, Consolas, monospace;
  color: var(--accent); font-size: 0.82rem; letter-spacing: 0.12em;
  margin-bottom: 14px;
}
.case h4 { font-size: clamp(19px, 0.7vw + 12px, 26px); line-height: 1.42; margin-bottom: 10px; }
.case p { color: var(--fg-dim); font-size: 0.9rem; margin-top: auto; }
/* 照片区（sticky 视口内，与卡片横移同屏） */
.case-photos { padding-inline: max(4vw, 20px); margin-top: 22px; }
.photo-lead {
  font-size: 0.8rem; letter-spacing: 0.26em; text-transform: uppercase;
  color: var(--fg-faint); margin-bottom: 14px;
}
.photo-row { display: flex; gap: 14px; }
.photo-row figure {
  flex: 1 1 0; height: clamp(170px, 30vh, 420px);
  border-radius: 16px; overflow: hidden;
  border: 1px solid var(--hair); background: var(--card);
}
.photo-row img { width: 100%; height: 100%; object-fit: cover; display: block; }

/* ---------- 关于北宸 · 荣誉徽章 ---------- */
.badge-row { display: grid; grid-template-columns: repeat(2, 1fr); gap: 16px; margin-top: clamp(70px, 11vh, 120px); }
.big-badge {
  border: 1px solid var(--hair); border-radius: 24px; background: var(--card);
  padding: 34px 32px;
  transition: transform 0.5s var(--ease), background-color 0.4s;
}
.big-badge:hover { transform: translateY(-5px); background: var(--card-hover); }
.big-badge .kicker {
  font-size: 0.68rem; letter-spacing: 0.26em; text-transform: uppercase;
  color: var(--accent); display: block; margin-bottom: 16px;
}
.big-badge h4 { font-size: clamp(19px, 1vw + 11px, 27px); line-height: 1.45; margin-bottom: 12px; }
.big-badge p { color: var(--fg-dim); font-size: 0.92rem; }

/* ---------- 响应式 ---------- */
@media (max-width: 1024px) {
  .chips, .cards, .qual-grid { grid-template-columns: repeat(2, 1fr); }
  .about-grid { grid-template-columns: 1fr; }
  .about-media { aspect-ratio: 16 / 9; max-height: 60vh; }
  .field-grid, .dv-stats { grid-template-columns: repeat(2, 1fr); }
  .command-grid { grid-template-columns: 1fr; }
  .geo-grid { grid-template-columns: repeat(2, 1fr); }
  .photo-row { grid-template-columns: repeat(3, 1fr); }
  .badge-row { grid-template-columns: 1fr; }
}

@media (max-width: 768px) {
  html { font-size: 15.5px; }
  .nav-links { display: none; }
  .menu-toggle { display: block; }
  .story { grid-template-columns: 1fr; }
  .story-visual { position: relative; top: 0; height: 52vh; }
  .step { min-height: 0; padding-block: 9vh; }
  .step.active { transform: none; }
  .chips, .cards, .qual-grid, .stats { grid-template-columns: 1fr; }
  .stats { gap: 26px; }
  .workflow { border-radius: 26px; }
  .flow b { width: 110px; height: 110px; font-size: 1rem; }
  .hero-meta { display: none; }
  .belief-media, .ops-media { aspect-ratio: 4 / 3; }
  .footer { flex-direction: column; align-items: flex-start; }
  .field-grid, .dv-stats, .geo-grid { grid-template-columns: repeat(2, 1fr); }
  .photo-row { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; }
  .photo-row figure { height: clamp(140px, 22vh, 300px); }
  .evolve-card { grid-template-columns: 1fr; gap: 16px; }
  .cases-scroll { height: auto !important; }
  .case-track-wrap { position: static; overflow-x: auto; padding-block: 24px; }
  .case-track { width: max-content; }
}

/* ---------- 降级 ---------- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.001s !important; transition-duration: 0.001s !important; }
  .manifesto .ch { opacity: 1; }
  .step { opacity: 1; transform: none; }
  .scroll-hint { animation: none; }
}