/* ============================================================
   UltiMaker Cura 中文官方网站 - 全局样式
   配色基于官方 logo：主蓝 #196EF0 / 深海军蓝 #0B2E63
   风格：扁平、现代、专业（无渐变滥用、无表情符号图标）
   ============================================================ */

/* ---------- 设计令牌 ---------- */
:root {
  --primary: #196EF0;
  --primary-600: #1559C9;
  --primary-700: #0F47A6;
  --navy: #0B2E63;
  --navy-deep: #071F45;
  --tint-50: #F5F9FE;
  --tint-100: #EAF2FD;
  --tint-200: #D8E6FA;
  --ink: #16233A;
  --body-c: #46536B;
  --muted: #6D7C96;
  --line: #E4EAF3;
  --white: #FFFFFF;
  --success: #17934F;
  --warn-bg: #FFF8E6;
  --radius-lg: 14px;
  --radius: 10px;
  --radius-sm: 7px;
  --shadow-sm: 0 1px 2px rgba(11, 46, 99, .05);
  --shadow-md: 0 2px 6px rgba(11, 46, 99, .07), 0 10px 28px rgba(11, 46, 99, .08);
  --container: 1200px;
  --header-h: 68px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", "Helvetica Neue",
    Arial, sans-serif;
}

/* ---------- 基础重置 ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.75;
  color: var(--body-c);
  background: var(--white);
  -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; height: auto; display: block; }
a { color: var(--primary); text-decoration: none; }
a:hover { color: var(--primary-600); }
h1, h2, h3, h4 { color: var(--ink); line-height: 1.3; margin: 0 0 .5em; font-weight: 700; }
h1 { font-size: 40px; letter-spacing: -.5px; }
h2 { font-size: 30px; letter-spacing: -.3px; }
h3 { font-size: 19px; }
h4 { font-size: 16px; }
p { margin: 0 0 1em; }
ul, ol { padding-left: 1.25em; margin: 0 0 1em; }
li { margin-bottom: .4em; }
table { border-collapse: collapse; width: 100%; }
:focus-visible { outline: 3px solid var(--primary); outline-offset: 2px; border-radius: 4px; }

.container { width: 100%; max-width: var(--container); margin: 0 auto; padding: 0 24px; }
.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;
}
.icon { width: 24px; height: 24px; flex: none; }

/* ---------- 顶部导航 ---------- */
.site-header {
  position: sticky; top: 0; z-index: 1000;
  background: rgba(255, 255, 255, .97);
  border-bottom: 1px solid var(--line);
  height: var(--header-h);
  transition: box-shadow .25s ease;
}
.site-header.is-scrolled { box-shadow: var(--shadow-md); }
.header-inner { display: flex; align-items: center; gap: 28px; height: var(--header-h); }
.brand { display: flex; align-items: center; gap: 11px; flex: none; }
.brand img { width: 36px; height: 36px; }
.brand-text {
  display: flex; flex-direction: column; line-height: 1.15;
  font-size: 17px; font-weight: 700; color: var(--ink); letter-spacing: -.2px;
}
.brand-text .brand-sub {
  font-size: 11px; font-weight: 500; color: var(--muted); letter-spacing: .5px;
}
.site-nav { display: flex; align-items: center; gap: 4px; margin-left: auto; }
.site-nav a {
  display: block; padding: 8px 15px; border-radius: var(--radius-sm);
  color: var(--body-c); font-weight: 500; font-size: 15px;
  transition: color .15s ease, background-color .15s ease;
}
.site-nav a:hover { color: var(--primary); background: var(--tint-100); }
.site-nav a.is-active { color: var(--primary); background: var(--tint-100); font-weight: 700; }
.header-actions { display: flex; align-items: center; gap: 12px; flex: none; }
.nav-toggle {
  display: none; flex-direction: column; justify-content: center; gap: 5px;
  width: 40px; height: 40px; padding: 9px; border: 1px solid var(--line);
  border-radius: var(--radius-sm); background: var(--white); cursor: pointer;
}
.nav-toggle span {
  display: block; height: 2px; width: 100%; background: var(--ink);
  border-radius: 2px; transition: transform .2s ease, opacity .2s ease;
}
.nav-toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 9px;
  padding: 11px 26px; border-radius: var(--radius-sm);
  font-family: inherit; font-size: 15px; font-weight: 700; line-height: 1.2;
  border: 1px solid transparent; cursor: pointer; white-space: nowrap;
  transition: background-color .15s ease, border-color .15s ease, color .15s ease,
    transform .15s ease, box-shadow .15s ease;
  text-decoration: none;
}
.btn:hover { text-decoration: none; }
.btn-primary { background: var(--primary); color: var(--white); }
.btn-primary:hover { background: var(--primary-600); color: var(--white); box-shadow: 0 6px 18px rgba(25, 110, 240, .32); }
.btn-primary:active { background: var(--primary-700); }
.btn-ghost { background: var(--white); color: var(--primary); border-color: var(--tint-200); }
.btn-ghost:hover { border-color: var(--primary); background: var(--tint-50); color: var(--primary-600); }
.btn-navy { background: var(--navy); color: var(--white); }
.btn-navy:hover { background: var(--navy-deep); color: var(--white); }
.btn-light { background: var(--white); color: var(--navy); }
.btn-light:hover { background: var(--tint-100); color: var(--primary); }
.btn-xl { padding: 16px 42px; font-size: 18px; border-radius: var(--radius); }
.btn-lg { padding: 14px 34px; font-size: 16px; }
.btn-sm { padding: 8px 18px; font-size: 14px; }
.btn-block { width: 100%; }
.btn .icon { width: 18px; height: 18px; }

/* ---------- 通用区块 ---------- */
.section { padding: 88px 0; }
.section-tint { background: var(--tint-50); }
.section-navy { background: var(--navy); color: #C9D8EE; }
.section-navy h2, .section-navy h3 { color: var(--white); }
.section-head { max-width: 760px; margin: 0 auto 52px; text-align: center; }
.eyebrow {
  display: inline-flex; align-items: center; gap: 8px;
  font-size: 13px; font-weight: 700; letter-spacing: 2px;
  color: var(--primary); text-transform: uppercase; margin-bottom: 14px;
}
.eyebrow::before { content: ""; width: 22px; height: 2px; background: var(--primary); }
.section-head .lead, .lead { font-size: 17px; color: var(--muted); margin: 0; }
.section-navy .section-head .lead { color: #A8BEE0; }

/* ---------- 首页 Hero ---------- */
.hero {
  position: relative; overflow: hidden;
  background: var(--tint-50);
  background-image: linear-gradient(var(--line) 1px, transparent 1px),
    linear-gradient(90deg, var(--line) 1px, transparent 1px);
  background-size: 44px 44px;
  background-position: center top;
}
.hero::before {
  content: ""; position: absolute; inset: 0;
  background: radial-gradient(ellipse 70% 90% at 50% -10%, rgba(255,255,255,0) 40%, var(--tint-50) 78%);
  pointer-events: none;
}
.hero-inner {
  position: relative; display: grid; grid-template-columns: 1.06fr .94fr;
  gap: 64px; align-items: center; padding: 96px 0 84px;
}
.hero-copy .hero-badge {
  display: inline-flex; align-items: center; gap: 8px;
  background: var(--white); border: 1px solid var(--tint-200);
  border-radius: 999px; padding: 6px 16px;
  font-size: 13px; font-weight: 600; color: var(--navy);
  box-shadow: var(--shadow-sm); margin-bottom: 22px;
}
.hero-badge .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--success); }
.hero h1 { margin-bottom: 18px; }
.hero h1 .accent { color: var(--primary); }
.hero-lead { font-size: 18px; max-width: 560px; margin-bottom: 34px; }
.hero-cta { display: flex; flex-wrap: wrap; gap: 14px; margin-bottom: 30px; }
.hero-meta { font-size: 13px; color: var(--muted); display: flex; flex-wrap: wrap; gap: 6px 20px; }
.hero-meta span { display: inline-flex; align-items: center; gap: 6px; }
.hero-meta .icon { width: 15px; height: 15px; color: var(--success); }

/* Hero 插画：切片分层示意（纯 CSS/SVG 扁平图形） */
.hero-visual { position: relative; }
.hero-visual svg { width: 100%; height: auto; }
.hero-visual .hv-card {
  background: var(--white); border: 1px solid var(--line);
  border-radius: var(--radius-lg); padding: 28px; box-shadow: var(--shadow-md);
}
.hv-caption {
  display: flex; justify-content: space-between; margin-top: 18px;
  font-size: 12.5px; color: var(--muted);
}
.hv-caption strong { color: var(--navy); }

/* 数据条 */
.stats-band {
  position: relative; border-top: 1px solid var(--line);
  background: var(--white);
}
.stats-grid {
  display: grid; grid-template-columns: repeat(4, 1fr);
  padding: 34px 0;
}
.stat-item { text-align: center; padding: 4px 18px; border-left: 1px solid var(--line); }
.stat-item:first-child { border-left: 0; }
.stat-num {
  font-size: 34px; font-weight: 800; color: var(--primary);
  letter-spacing: -1px; line-height: 1.15; font-variant-numeric: tabular-nums;
}
.stat-num .unit { font-size: 17px; font-weight: 700; }
.stat-label { font-size: 13.5px; color: var(--muted); margin-top: 2px; }

/* ---------- 卡片网格 ---------- */
.grid { display: grid; gap: 24px; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }
.card {
  background: var(--white); border: 1px solid var(--line);
  border-radius: var(--radius-lg); padding: 30px 28px;
  transition: border-color .18s ease, box-shadow .18s ease, transform .18s ease;
}
.card:hover {
  border-color: var(--tint-200); box-shadow: var(--shadow-md);
  transform: translateY(-3px);
}
.card .icon-tile {
  display: flex; align-items: center; justify-content: center;
  width: 50px; height: 50px; border-radius: 12px;
  background: var(--tint-100); color: var(--primary); margin-bottom: 18px;
}
.card .icon-tile .icon { width: 26px; height: 26px; }
.card h3 { margin-bottom: 8px; }
.card p { margin: 0; font-size: 14.5px; color: var(--body-c); }
.card .card-link {
  display: inline-flex; align-items: center; gap: 6px;
  font-size: 14px; font-weight: 700; margin-top: 14px;
}
.card .card-link .icon { width: 15px; height: 15px; transition: transform .15s ease; }
.card .card-link:hover .icon { transform: translateX(3px); }

/* 使用场景卡片 */
.scenario-card { position: relative; overflow: hidden; }
.scenario-card .scene-tag {
  position: absolute; top: 0; right: 0;
  background: var(--tint-100); color: var(--primary);
  font-size: 12px; font-weight: 700; letter-spacing: 1px;
  padding: 6px 14px; border-bottom-left-radius: 10px;
}
.scenario-card ul { margin: 12px 0 0; padding-left: 0; list-style: none; }
.scenario-card ul li {
  position: relative; padding-left: 22px; font-size: 14px; color: var(--body-c);
}
.scenario-card ul li::before {
  content: ""; position: absolute; left: 2px; top: 9px;
  width: 7px; height: 7px; border-radius: 2px; background: var(--primary);
}

/* ---------- 流程步骤 ---------- */
.steps { display: grid; grid-template-columns: repeat(5, 1fr); gap: 18px; counter-reset: step; }
.step {
  position: relative; background: var(--white); border: 1px solid var(--line);
  border-radius: var(--radius-lg); padding: 26px 22px 22px;
}
.step::before {
  counter-increment: step; content: counter(step, decimal-leading-zero);
  display: inline-block; font-size: 26px; font-weight: 800; color: var(--tint-200);
  line-height: 1; margin-bottom: 12px; letter-spacing: -1px;
}
.step h4 { margin-bottom: 6px; }
.step p { margin: 0; font-size: 13.5px; color: var(--muted); }
.steps-flow { position: relative; }
.step-arrow {
  position: absolute; top: 50%; right: -14px; transform: translateY(-50%);
  width: 16px; height: 16px; color: var(--tint-200); z-index: 1;
}

/* ---------- 徽章 / 标签 ---------- */
.chip {
  display: inline-flex; align-items: center; gap: 6px;
  background: var(--tint-100); color: var(--primary);
  border-radius: 999px; padding: 3px 12px;
  font-size: 12.5px; font-weight: 700;
}
.chip-green { background: #E6F5ED; color: var(--success); }
.chip-navy { background: var(--navy); color: #C9D8EE; }

/* ---------- 页面内首屏（子页） ---------- */
.page-hero {
  background: var(--tint-50);
  background-image: linear-gradient(var(--line) 1px, transparent 1px),
    linear-gradient(90deg, var(--line) 1px, transparent 1px);
  background-size: 44px 44px;
  border-bottom: 1px solid var(--line);
  padding: 58px 0 54px;
}
.page-hero-inner { max-width: 860px; }
.breadcrumb { display: flex; flex-wrap: wrap; gap: 6px; font-size: 13px; color: var(--muted); margin-bottom: 18px; }
.breadcrumb a { color: var(--muted); }
.breadcrumb a:hover { color: var(--primary); }
.breadcrumb .sep { color: var(--tint-200); }
.page-hero h1 { font-size: 34px; margin-bottom: 12px; }
.page-hero .lead { font-size: 16.5px; max-width: 720px; }
.page-hero-meta { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 20px; }

/* ---------- 下载平台卡片 ---------- */
.os-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.os-card {
  background: var(--white); border: 1px solid var(--line);
  border-radius: var(--radius-lg); padding: 34px 30px; text-align: center;
  transition: border-color .18s ease, box-shadow .18s ease;
}
.os-card:hover { border-color: var(--primary); box-shadow: var(--shadow-md); }
.os-card .os-icon {
  display: flex; align-items: center; justify-content: center;
  width: 64px; height: 64px; margin: 0 auto 16px;
  border-radius: 16px; background: var(--tint-100); color: var(--primary);
}
.os-card .os-icon .icon { width: 32px; height: 32px; }
.os-card h3 { margin-bottom: 4px; }
.os-card .os-arch { font-size: 13px; color: var(--muted); margin-bottom: 18px; }
.os-card .os-spec {
  display: flex; flex-direction: column; gap: 7px;
  border-top: 1px solid var(--line); border-bottom: 1px solid var(--line);
  padding: 14px 0; margin-bottom: 22px; font-size: 13.5px;
}
.os-card .os-spec li { list-style: none; margin: 0; display: flex; justify-content: space-between; gap: 10px; }
.os-card .os-spec li span:first-child { color: var(--muted); }
.os-card .os-spec li span:last-child { color: var(--ink); font-weight: 600; }

/* ---------- 表格 ---------- */
.table-wrap { overflow-x: auto; border: 1px solid var(--line); border-radius: var(--radius-lg); background: var(--white); }
.tbl { min-width: 640px; font-size: 14.5px; }
.tbl th, .tbl td { padding: 14px 20px; text-align: left; border-bottom: 1px solid var(--line); }
.tbl thead th { background: var(--tint-50); color: var(--ink); font-weight: 700; white-space: nowrap; }
.tbl tbody tr:last-child td { border-bottom: 0; }
.tbl td.row-label { color: var(--ink); font-weight: 600; white-space: nowrap; }
.tbl td { color: var(--body-c); }

/* ---------- 时间线 ---------- */
.timeline { position: relative; padding-left: 34px; }
.timeline::before {
  content: ""; position: absolute; left: 8px; top: 6px; bottom: 6px;
  width: 2px; background: var(--tint-200);
}
.timeline-item { position: relative; padding-bottom: 30px; }
.timeline-item:last-child { padding-bottom: 0; }
.timeline-item::before {
  content: ""; position: absolute; left: -33px; top: 7px;
  width: 14px; height: 14px; border-radius: 50%;
  background: var(--white); border: 3px solid var(--primary);
}
.timeline-item .tl-year { font-size: 14px; font-weight: 800; color: var(--primary); letter-spacing: 1px; }
.timeline-item h3 { font-size: 17px; margin: 2px 0 4px; }
.timeline-item p { margin: 0; font-size: 14.5px; color: var(--muted); }

/* ---------- FAQ 手风琴 ---------- */
.faq-list { max-width: 860px; margin: 0 auto; }
.faq-item { border: 1px solid var(--line); border-radius: var(--radius); background: var(--white); margin-bottom: 14px; overflow: hidden; }
.faq-q {
  display: flex; align-items: center; justify-content: space-between; gap: 16px;
  width: 100%; padding: 18px 22px; background: none; border: 0;
  font-family: inherit; font-size: 16px; font-weight: 700; color: var(--ink);
  text-align: left; cursor: pointer;
}
.faq-q:hover { color: var(--primary); }
.faq-q .icon { width: 20px; height: 20px; color: var(--primary); transition: transform .2s ease; flex: none; }
.faq-item.is-open .faq-q .icon { transform: rotate(45deg); }
.faq-a { display: none; padding: 0 22px 20px; font-size: 14.5px; color: var(--body-c); }
.faq-item.is-open .faq-a { display: block; }

/* ---------- 功能行（图标+文字） ---------- */
.feature-row {
  display: grid; grid-template-columns: 56px 1fr; gap: 20px;
  padding: 26px 0; border-bottom: 1px solid var(--line);
}
.feature-row:last-child { border-bottom: 0; }
.feature-row .icon-tile {
  width: 56px; height: 56px; border-radius: 14px;
  background: var(--tint-100); color: var(--primary);
  display: flex; align-items: center; justify-content: center;
}
.feature-row h3 { margin-bottom: 6px; }
.feature-row p { margin: 0; font-size: 14.5px; }
.feature-row .chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }

/* ---------- CTA 横幅 ---------- */
.cta-banner {
  background: var(--navy); border-radius: var(--radius-lg);
  padding: 56px 56px; display: flex; align-items: center;
  justify-content: space-between; gap: 40px; flex-wrap: wrap;
}
.cta-banner h2 { color: var(--white); margin-bottom: 8px; }
.cta-banner p { color: #A8BEE0; margin: 0; max-width: 560px; }
.cta-banner .btn-light:hover { box-shadow: 0 6px 18px rgba(255,255,255,.18); }

/* ---------- 版本历史 ---------- */
.release-item {
  display: grid; grid-template-columns: 130px 1fr; gap: 24px;
  padding: 24px 0; border-bottom: 1px solid var(--line);
}
.release-item:last-child { border-bottom: 0; }
.release-item .rel-ver { font-size: 20px; font-weight: 800; color: var(--primary); }
.release-item .rel-date { font-size: 13px; color: var(--muted); margin-top: 2px; }
.release-item ul { margin: 0; padding-left: 1.2em; font-size: 14.5px; }
.release-item .rel-note { font-size: 14.5px; margin: 0; }

/* ---------- 页脚 ---------- */
.site-footer { background: var(--navy-deep); color: #9FB3D4; margin-top: 0; }
.footer-top { display: grid; grid-template-columns: 1.4fr 1fr 1fr 1fr; gap: 48px; padding: 64px 0 44px; }
.footer-brand { display: flex; align-items: center; gap: 11px; margin-bottom: 18px; }
.footer-brand img { width: 34px; height: 34px; }
.footer-brand .brand-text { color: var(--white); }
.footer-brand .brand-text .brand-sub { color: #7C93BC; }
.footer-desc { font-size: 13.5px; line-height: 1.8; margin: 0 0 16px; }
.footer-col h4 { color: var(--white); font-size: 14px; letter-spacing: 1px; margin-bottom: 16px; }
.footer-col ul { list-style: none; padding: 0; margin: 0; }
.footer-col ul li { margin-bottom: 9px; }
.footer-col a { color: #9FB3D4; font-size: 13.5px; }
.footer-col a:hover { color: var(--white); }
.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, .1);
  padding: 22px 0; display: flex; flex-wrap: wrap;
  align-items: center; justify-content: space-between; gap: 10px;
  font-size: 12.5px; color: #7C93BC;
}
.footer-bottom .links { display: flex; flex-wrap: wrap; gap: 18px; }
.footer-bottom a { color: #9FB3D4; }
.footer-bottom a:hover { color: var(--white); }

/* ---------- 下载弹窗 ---------- */
.modal { position: fixed; inset: 0; z-index: 2000; display: none; }
.modal.is-open { display: block; left: 0;
  right: 0;
  top: 0;
  bottom: 0; }
  button { outline: none } 
.modal-backdrop { position: absolute; inset: 0; background: rgba(7, 31, 69, .55); }
.modal-dialog {
  position: relative; width: min(560px, calc(100vw - 40px));
  margin: 8vh auto 0; background: var(--white);
  border-radius: var(--radius-lg); box-shadow: 0 24px 80px rgba(7, 31, 69, .35);
  max-height: 86vh; overflow-y: auto; animation: modal-in .22s ease;
}
@keyframes modal-in { from { opacity: 0; transform: translateY(14px); } to { opacity: 1; transform: none; } }
.modal-close {
  position: absolute; top: 14px; right: 14px; width: 36px; height: 36px;
  display: flex; align-items: center; justify-content: center;
  background: var(--tint-50); border: 0; border-radius: 50%;
  color: var(--muted); cursor: pointer; transition: background-color .15s ease, color .15s ease;
}
.modal-close:hover { background: var(--tint-100); color: var(--ink); }
.modal-close .icon { width: 18px; height: 18px; }
.modal-body { padding: 34px 38px 30px; }
.modal-body h3 { font-size: 22px; margin-bottom: 4px; }
.modal-version { font-size: 13px; color: var(--muted); margin: 0 0 22px; }
.os-tabs { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; margin-bottom: 20px; }
.os-tab {
  display: flex; align-items: center; justify-content: center; gap: 8px;
  padding: 10px 8px; border: 1px solid var(--line); border-radius: var(--radius-sm);
  background: var(--white); color: var(--body-c);
  font-family: inherit; font-size: 14px; font-weight: 600; cursor: pointer;
  transition: border-color .15s ease, color .15s ease, background-color .15s ease;
}
.os-tab .icon { width: 17px; height: 17px; }
.os-tab:hover { border-color: var(--primary); color: var(--primary); }
.os-tab.is-active { border-color: var(--primary); background: var(--tint-100); color: var(--primary); font-weight: 700; }
.modal-file {
  display: flex; align-items: center; justify-content: center; gap: 8px;
  font-size: 12.5px; color: var(--muted); margin: 14px 0 22px;
}
.modal-file .icon { width: 14px; height: 14px; }
.modal-qr {
  border-top: 1px solid var(--line); padding-top: 24px;
  display: grid; grid-template-columns: 1fr 1fr; gap: 18px;
}
.qr-item { text-align: center; }
.qr-item img {
  width: 160px; height: 160px; margin: 0 auto 10px;
  border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 8px;
  background: var(--white);
}
.qr-item .qr-title { font-size: 13.5px; font-weight: 700; color: var(--ink); margin: 0; }
.qr-item .qr-sub { font-size: 12px; color: var(--muted); margin: 2px 0 0; }
.modal-note {
  margin: 22px 0 0; padding: 12px 16px; background: var(--warn-bg);
  border-radius: var(--radius-sm); font-size: 12.5px; color: #8A6A1F; line-height: 1.7;
}

/* ---------- 返回顶部 ---------- */
.back-top {
  position: fixed; right: 26px; bottom: 30px; z-index: 1500;
  width: 44px; height: 44px; border-radius: 12px;
  background: var(--white); border: 1px solid var(--line);
  color: var(--primary); display: flex; align-items: center; justify-content: center;
  cursor: pointer; box-shadow: var(--shadow-md);
  opacity: 0; visibility: hidden; transform: translateY(8px);
  transition: opacity .2s ease, transform .2s ease, visibility .2s;
}
.back-top.is-show { opacity: 1; visibility: visible; transform: none; }
.back-top:hover { border-color: var(--primary); }
.back-top .icon { width: 20px; height: 20px; }

/* ---------- 说明/引用块 ---------- */
.note-block {
  display: flex; gap: 14px; background: var(--tint-100);
  border-left: 3px solid var(--primary);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  padding: 18px 22px; font-size: 14px; color: var(--navy);
}
.note-block .icon { width: 20px; height: 20px; color: var(--primary); margin-top: 3px; }

/* ---------- 工具类 ---------- */
.text-center { text-align: center; }
.mt-0 { margin-top: 0; } .mb-0 { margin-bottom: 0; }
.mt-24 { margin-top: 24px; } .mt-40 { margin-top: 40px; }
.flex-center { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }

/* ---------- 响应式 ---------- */
@media (max-width: 1020px) {
  .hero-inner { grid-template-columns: 1fr; padding: 64px 0 56px; gap: 44px; }
  .hero-lead { max-width: 640px; }
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .steps { grid-template-columns: repeat(2, 1fr); }
  .step-arrow { display: none; }
  .os-grid { grid-template-columns: 1fr; }
  .footer-top { grid-template-columns: 1fr 1fr; gap: 36px; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); row-gap: 22px; }
  .stat-item:nth-child(3) { border-left: 0; }
}
@media (max-width: 680px) {
  body { font-size: 15px; }
  h1 { font-size: 30px; } h2 { font-size: 24px; }
  .section { padding: 60px 0; }
  .grid-3, .grid-2 { grid-template-columns: 1fr; }
  .grid-4 { grid-template-columns: 1fr; }
  .steps { grid-template-columns: 1fr; }
  .nav-toggle { display: flex; }
  .site-nav {
    display: none; position: absolute; top: var(--header-h); left: 0; right: 0;
    flex-direction: column; align-items: stretch; gap: 2px;
    background: var(--white); border-bottom: 1px solid var(--line);
    padding: 12px 20px 18px; box-shadow: var(--shadow-md);
  }
  .site-nav.is-open { display: flex; }
  .site-nav a { padding: 12px 14px; border-radius: var(--radius-sm); }
  .header-actions .btn { display: none; }
  .stats-grid { grid-template-columns: 1fr 1fr; }
  .stat-item { border-left: 0; }
  .cta-banner { padding: 38px 26px; }
  .modal-body { padding: 28px 22px 24px; }
  .modal-qr { gap: 10px; }
  .release-item { grid-template-columns: 1fr; gap: 4px; }
  .footer-top { grid-template-columns: 1fr; gap: 30px; padding: 48px 0 34px; }
  .hero-visual { display: none; }
}

/* ---------- 动效偏好 ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: .01ms !important; transition-duration: .01ms !important; }
}

/* ---------- 打印 ---------- */
@media print {
  .site-header, .site-footer, .back-top, .modal, .hero-cta { display: none !important; }
}