/* =========================================================
   MILITEC UI Design System — shared across all pages
   视觉统一规范 / Design Tokens + 通用组件
   纯本地、零外部字体依赖（思源黑体优先，系统黑体兜底）
   ========================================================= */
:root {
  /* 品牌色 */
  --brand: #cc0000;
  --brand-light: #e60000;
  --brand-dark: #990000;
  --brand-tint: rgba(204, 0, 0, 0.06);

  /* 中性灰阶 */
  --gray-50: #f9f9f9;
  --gray-100: #f0f0f0;
  --gray-150: #f5f5f5;
  --gray-200: #e6e6e6;
  --gray-300: #d4d4d4;
  --gray-400: #999;
  --gray-500: #777;
  --gray-600: #555;
  --gray-700: #444;
  --gray-800: #2a2a2a;
  --gray-900: #1a1a1a;

  /* 字体栈：中文优先思源黑体 / Noto Sans CJK，无则系统黑体兜底 */
  --font-sans: "Source Han Sans SC", "Noto Sans CJK SC", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "WenQuanYi Micro Hei",
    "Helvetica Neue", Arial, sans-serif;
  --font-en: "Helvetica Neue", Arial, "Source Han Sans SC", "Noto Sans CJK SC",
    sans-serif;

  /* 字号层级（固定） */
  --fs-hero: clamp(30px, 5.5vw, 52px);
  --fs-h1: clamp(26px, 4vw, 38px);
  --fs-h2: clamp(22px, 3vw, 30px);
  --fs-h3: 20px;
  --fs-h4: 16px;
  --fs-body: 15px;
  --fs-small: 13px;
  --fs-tiny: 11px;

  /* 行距：正文 1.6-1.8，避免拥挤 */
  --lh-tight: 1.4;
  --lh-base: 1.75;
  --lh-relaxed: 1.8;

  /* 圆角 / 阴影 */
  --radius: 10px;
  --radius-sm: 6px;
  --shadow-card: 0 6px 22px rgba(0, 0, 0, 0.06);
  --shadow-hover: 0 16px 48px rgba(0, 0, 0, 0.1);

  /* 容器 */
  --container: 1200px;
}

/* ---------- 基础 ---------- */
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-sans);
  color: var(--gray-800);
  line-height: var(--lh-base);
  background: #fff;
  -webkit-font-smoothing: antialiased;
}
a { text-decoration: none; color: inherit; }
img { max-width: 100%; display: block; }

/* ---------- 通用排版 ---------- */
.container { max-width: var(--container); margin: 0 auto; padding: 0 40px; }
.section { padding: 88px 0; }
.section-head { max-width: 760px; margin: 0 auto 48px; text-align: center; }
.section-label {
  font-size: var(--fs-tiny); font-weight: 600; color: var(--brand);
  letter-spacing: 0.22em; text-transform: uppercase; margin-bottom: 14px;
}
.section-title {
  font-size: var(--fs-h2); font-weight: 300; color: var(--gray-900);
  line-height: var(--lh-tight); margin-bottom: 14px;
}
.section-title strong { color: var(--brand); font-weight: 600; }
.section-desc { color: var(--gray-500); font-size: var(--fs-body); line-height: var(--lh-relaxed); }

/* 正文段落：短段落 + 项目符号 */
.prose p { margin-bottom: 16px; line-height: var(--lh-relaxed); color: var(--gray-600); }
.prose h3 { font-size: var(--fs-h3); color: var(--gray-900); margin: 28px 0 12px; font-weight: 600; }
.prose ul { margin: 0 0 16px; padding-left: 20px; }
.prose ul li { margin-bottom: 8px; line-height: var(--lh-relaxed); color: var(--gray-600); }

/* ---------- 统一 CTA 按钮 ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  font-family: inherit; font-size: var(--fs-body); font-weight: 500;
  padding: 13px 30px; border-radius: var(--radius); cursor: pointer;
  border: 1.5px solid var(--brand); transition: all 0.25s ease; line-height: 1;
  white-space: nowrap;
}
.btn-primary { background: var(--brand); color: #fff; }
.btn-primary:hover { background: var(--brand-dark); border-color: var(--brand-dark); transform: translateY(-1px); box-shadow: var(--shadow-card); }
.btn-ghost { background: #fff; color: var(--brand); }
.btn-ghost:hover { background: var(--brand-tint); transform: translateY(-1px); }
.btn-lg { padding: 16px 42px; font-size: 17px; }
.btn-block { width: 100%; }

/* ---------- 顶部导航（共享） ---------- */
.sn-navbar {
  position: fixed; top: 0; left: 0; width: 100%; height: 64px;
  background: rgba(255, 255, 255, 0.96); backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--gray-100); z-index: 1000;
}
.sn-inner { max-width: var(--container); margin: 0 auto; height: 64px; padding: 0 40px;
  display: flex; align-items: center; justify-content: space-between; }
.sn-logo { display: flex; align-items: center; gap: 10px; text-decoration: none; flex-shrink: 0; }
.sn-logo-mark { font-size: 20px; font-weight: 700; color: var(--brand); letter-spacing: 0.06em; line-height: 1; }
.sn-logo-mark small { font-weight: 300; font-size: 12px; letter-spacing: 0.12em; margin-left: 4px; color: var(--gray-500); }
.sn-logo-mark sup { font-size: 0.5em; font-weight: 700; top: -0.7em; margin-left: 1px; }
.sn-logo img { height: 32px; }
/* 导航分隔线：物理切割「密力铁油品中心」与「MILITEC® 赛车机械研究院」两大业务板块 */
.sn-divider { width: 1px; height: 22px; background: var(--gray-200); margin: 0 6px; align-self: center; }
/* 研究院入口：红色 CTA，与油品中心在视觉权重上均衡且突出 */
.sn-links a.sn-cta {
  color: #fff; background: var(--brand); padding: 8px 16px; border-radius: 6px; font-weight: 600; letter-spacing: 0.02em;
}
.sn-links a.sn-cta:hover, .sn-links a.sn-cta.active { color: #fff; background: var(--brand-dark); }
.sn-links a.sn-cta.active::after { display: none; }
.sn-right { display: flex; align-items: center; gap: 22px; }
.sn-links { list-style: none; display: flex; gap: 28px; margin: 0; padding: 0; }
.sn-links a {
  font-size: var(--fs-small); color: var(--gray-600); letter-spacing: 0.04em;
  transition: color 0.2s; padding: 6px 0; position: relative; font-family: inherit;
}
.sn-links a:hover, .sn-links a.active { color: var(--brand); }
.sn-links a.active::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -2px; height: 2px; background: var(--brand);
}

/* 二级子导航 */
.sn-dropdown { position: relative; }
/* 透明桥接区：覆盖触发项到下拉菜单之间的间隙，防止 hover 断裂 */
.sn-dropdown::after {
  content: ""; position: absolute; top: 100%; left: 0; width: 100%; height: 8px;
  background: transparent; z-index: 1099;
}
.sn-dropdown > a { display: flex; align-items: center; gap: 4px; }
.sn-caret { font-size: 9px; color: var(--gray-400); line-height: 1; }
.sn-submenu {
  opacity: 0; visibility: hidden;
  transition: opacity 0.12s ease, visibility 0.12s ease;
  position: absolute; top: calc(100% + 6px); left: 0;
  background: #fff; border: 1px solid var(--gray-200); border-radius: var(--radius-sm);
  box-shadow: var(--shadow-card); min-width: 220px; z-index: 1100; padding: 6px; list-style: none;
}
.sn-submenu a {
  display: block; padding: 9px 14px; font-size: var(--fs-small); color: var(--gray-700);
  border-radius: var(--radius-sm); transition: background 0.15s, color 0.15s;
  white-space: nowrap;
}
.sn-submenu a:hover { background: var(--gray-100); color: var(--brand); }
.sn-dropdown:hover .sn-submenu { opacity: 1; visibility: visible; }

/* 移动端子导航 */
@media (max-width: 900px) {
  .sn-submenu { position: static; display: none; margin-top: 0; box-shadow: none; border: none; padding: 0 0 0 18px; background: var(--gray-50); border-radius: 0; min-width: auto; }
  .sn-submenu.show, .sn-dropdown.open .sn-submenu { display: block; }
  .sn-submenu a { padding: 12px 18px; border-bottom: 1px solid var(--gray-100); border-radius: 0; }
}

/* 语言切换：文字为主 + 国旗辅助 + 选中高亮 */
.sn-lang { position: relative; }
.sn-lang-btn {
  display: inline-flex; align-items: center; gap: 7px; background: var(--gray-50);
  border: 1px solid var(--gray-200); border-radius: var(--radius-sm);
  padding: 7px 13px; font-size: var(--fs-small); font-family: inherit; color: var(--gray-800);
  cursor: pointer; transition: border-color 0.2s;
}
.sn-lang-btn:hover { border-color: var(--gray-400); }
.sn-lang-btn .sn-flag { font-size: 15px; line-height: 1; }
.sn-lang-btn .sn-arrow { font-size: 9px; color: var(--gray-400); }
.sn-lang-menu {
  display: none; position: absolute; top: 100%; right: 0; margin-top: 8px;
  background: #fff; border: 1px solid var(--gray-200); border-radius: var(--radius-sm);
  box-shadow: var(--shadow-card); min-width: 168px; z-index: 1100; padding: 6px;
}
.sn-lang-menu.show { display: block; }
.sn-lang-opt {
  display: flex; align-items: center; gap: 10px; width: 100%; padding: 9px 12px;
  border: none; background: none; font-size: var(--fs-small); font-family: inherit;
  color: var(--gray-700); cursor: pointer; border-radius: var(--radius-sm); text-align: left;
}
.sn-lang-opt:hover { background: var(--gray-100); }
.sn-lang-opt.active { color: var(--brand); font-weight: 600; background: var(--brand-tint); }
.sn-lang-opt .sn-flag { font-size: 16px; line-height: 1; }

.sn-toggle { display: none; background: none; border: none; cursor: pointer; padding: 6px; flex-direction: column; gap: 5px; }
.sn-toggle span { display: block; width: 24px; height: 2px; background: var(--gray-800); transition: 0.3s; }

/* ---------- 面包屑（固定导航下方，需让位 64px） ---------- */
.breadcrumb { background: var(--gray-50); border-bottom: 1px solid var(--gray-100); padding: 14px 0; margin-top: 64px; font-size: var(--fs-small); color: var(--gray-500); }
.breadcrumb .container { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.breadcrumb a { color: var(--gray-500); transition: color 0.2s; }
.breadcrumb a:hover { color: var(--brand); }
.breadcrumb .sep { color: var(--gray-300); }
.breadcrumb .current { color: var(--gray-800); font-weight: 500; }

/* RTL：导航与语言菜单镜像 */
[dir="rtl"] .sn-lang-menu { right: auto; left: 0; }
[dir="rtl"] .sn-links a.active::after { left: 0; right: 0; }

/* ---------- 内容区顶部（给固定导航让位） ---------- */
.page-top { padding-top: 64px; }

/* ---------- 产品卡片（统一） ---------- */
.card-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 28px; }
.ucard {
  background: #fff; border: 1px solid var(--gray-200); border-radius: var(--radius);
  padding: 36px 30px; transition: all 0.3s ease; display: flex; flex-direction: column;
}
.ucard:hover { box-shadow: var(--shadow-hover); transform: translateY(-3px); border-color: transparent; }
.ucard-thumb {
  width: 100%; aspect-ratio: 4 / 3; object-fit: contain; background: #fff;
  border-radius: var(--radius-sm); margin-bottom: 20px; border: 1px solid var(--gray-100);
}
.ucard h3 { font-size: var(--fs-h3); font-weight: 600; color: var(--gray-900); margin-bottom: 6px; }
.ucard .model { font-size: var(--fs-small); color: var(--gray-400); margin-bottom: 14px; letter-spacing: 0.04em; }
.ucard .spec-list { list-style: none; padding: 0; margin: 0 0 18px; }
.ucard .spec-list li { display: flex; justify-content: space-between; gap: 12px; padding: 8px 0; border-bottom: 1px dashed var(--gray-150); font-size: var(--fs-small); }
.ucard .spec-list li .k { color: var(--gray-500); }
.ucard .spec-list li .v { color: var(--gray-800); font-weight: 500; text-align: right; }
.ucard .desc { color: var(--gray-600); font-size: var(--fs-small); line-height: var(--lh-relaxed); margin-bottom: 18px; flex: 1; }
.ucard .btn { margin-top: auto; align-self: flex-start; }

/* ---------- 行业背书 / 制造商墙 ---------- */
.proof { background: var(--gray-50); border-top: 1px solid var(--gray-100); border-bottom: 1px solid var(--gray-100); }
.proof .container { max-width: var(--container); }
.proof-head { max-width: 760px; margin: 0 auto 36px; text-align: center; }
.proof-cols { display: grid; grid-template-columns: 1.55fr 1fr; gap: 44px; align-items: start; }
.mfg-group { margin-bottom: 22px; }
.mfg-cat { display: block; font-size: var(--fs-small); font-weight: 600; color: var(--gray-800); margin-bottom: 11px; letter-spacing: 0.04em; }
.mfg-cat::before { content: ""; display: inline-block; width: 4px; height: 14px; background: var(--brand); margin-right: 9px; vertical-align: -2px; border-radius: 2px; }
.mfg-chips { display: flex; flex-wrap: wrap; gap: 8px; }
.mfg-chips span { font-size: var(--fs-tiny); color: var(--gray-600); background: #fff; border: 1px solid var(--gray-200); border-radius: 100px; padding: 6px 13px; white-space: nowrap; }
.proof-cert { background: #fff; border: 1px solid var(--gray-200); border-radius: var(--radius); padding: 30px 28px; }
.proof-cert h3 { font-size: var(--fs-h4); color: var(--gray-900); margin-bottom: 12px; font-weight: 600; }
.proof-cert p { font-size: var(--fs-small); color: var(--gray-600); line-height: var(--lh-relaxed); margin-bottom: 16px; }
.proof-list { list-style: none; padding: 0; margin: 0; }
.proof-list li { position: relative; padding-left: 22px; margin-bottom: 11px; font-size: var(--fs-small); color: var(--gray-700); line-height: var(--lh-base); }
.proof-list li::before { content: "✓"; position: absolute; left: 0; top: 0; color: var(--brand); font-weight: 700; }

/* ---------- 首页信任背书带 ---------- */
.trust-strip { background: var(--gray-900); color: #fff; padding: 46px 0; }
.trust-strip .trust-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 26px; }
.trust-item { text-align: center; padding: 0 14px; border-left: 1px solid #333; }
.trust-item:first-child { border-left: none; }
.trust-num { font-size: 15px; font-weight: 700; color: #fff; line-height: 1.5; margin-bottom: 8px; letter-spacing: 0.02em; }
.trust-num .accent { color: var(--brand-light); }
.trust-label { font-size: var(--fs-small); color: #cfcfcf; line-height: var(--lh-base); }

/* ---------- 页脚（共享） ---------- */
.site-footer { background: var(--gray-900); color: #fff; padding: 56px 0 28px; }
.site-footer .container { max-width: var(--container); }
.ft-grid { display: grid; grid-template-columns: 1.4fr 1fr 1fr 1fr; gap: 40px; }
.ft-brand { font-size: 22px; font-weight: 700; letter-spacing: 0.06em; }
.ft-brand span { font-weight: 300; font-size: 13px; letter-spacing: 0.14em; margin-left: 8px; color: var(--gray-400); }
.ft-tag { color: var(--gray-400); font-size: var(--fs-small); margin-top: 14px; line-height: var(--lh-relaxed); max-width: 280px; }
.ft-col h4 { font-size: var(--fs-small); color: #ccc; font-weight: 600; margin-bottom: 14px; letter-spacing: 0.05em; text-transform: uppercase; }
.ft-col a, .ft-col p { display: block; color: #ccc; font-size: var(--fs-small); line-height: 1.9; transition: color 0.2s; }
.ft-col a:hover { color: #fff; }
.ft-cols-links a { color: var(--gray-400); }
.ft-bottom { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 10px; margin-top: 40px; padding-top: 22px; border-top: 1px solid #333; color: var(--gray-400); font-size: var(--fs-tiny); }
.ft-bottom a { color: var(--gray-400); }
.ft-bottom a:hover { color: #fff; }
/* 官网入口（醒目） */
.official-link {
  display: inline-block;
  margin-top: 8px;
  padding: 6px 14px;
  background: var(--brand);
  color: #fff !important;
  border-radius: 6px;
  font-weight: 600;
  font-size: 13px;
  line-height: 1.4;
  text-decoration: none !important;
  transition: background .2s ease, transform .08s ease;
}
.official-link:hover { background: #a30000; transform: translateY(-1px); color: #fff !important; }
.official-link::after { content: " ↗"; font-weight: 400; }

/* ---------- 移动端适配 ---------- */
@media (max-width: 900px) {
  .container { padding: 0 22px; }
  .section { padding: 60px 0; }
  .sn-links {
    position: fixed; top: 64px; left: 0; width: 100%; flex-direction: column; gap: 0;
    background: #fff; display: none; box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08); padding: 8px 0;
  }
  .sn-links.show { display: flex; }
  .sn-links a { display: block; padding: 15px 24px; border-bottom: 1px solid var(--gray-100); font-size: 15px; }
  .sn-links a.active::after { display: none; }
  .sn-toggle { display: flex; }
  .sn-right { gap: 12px; }
  .ft-grid { grid-template-columns: 1fr 1fr; gap: 28px; }
  .ft-brand, .ft-tag { grid-column: 1 / -1; }
  .proof-cols { grid-template-columns: 1fr; gap: 30px; }
  .trust-strip .trust-grid { grid-template-columns: repeat(2, 1fr); gap: 26px 18px; }
  .trust-item { border-left: none; padding: 12px 8px; }
}
@media (max-width: 520px) {
  .ft-grid { grid-template-columns: 1fr; }
  .btn-lg { padding: 15px 32px; font-size: 16px; }
  .trust-strip .trust-grid { grid-template-columns: 1fr; }
  .trust-item { padding: 12px 0; border-left: none; }
}