/* ============================================================
   中航华信官网 — base.css
   设计令牌 / reset / 排版 / 按钮 / 章节标题 / reveal 动画
   ============================================================ */

:root {
  /* 色板 */
  --navy: #0B2A4A;
  --navy-deep: #061E36;
  --blue-bright: #1E5AA8;
  --gray-bg: #F4F6F9;
  --gold: #C9A54C;
  --gold-soft: #E3C87E;
  --text-dark: #16212B;
  --text-gray: #5A6874;
  --text-light: #E8EEF5;
  --line: #E3E8EF;
  --card: #FFFFFF;

  /* 字体 */
  --font-cn: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB",
             "Microsoft YaHei", "Noto Sans SC", "Source Han Sans SC", sans-serif;
  --font-en: "Helvetica Neue", Helvetica, Arial, "Segoe UI", sans-serif;

  /* 尺寸 */
  --nav-h: 76px;
  --radius: 8px;
  --shadow-card: 0 10px 34px rgba(6, 30, 54, .08);
  --shadow-card-hover: 0 18px 44px rgba(6, 30, 54, .14);
  --ease: cubic-bezier(.22, .61, .36, 1);
}

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

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

body {
  font-family: var(--font-cn);
  font-size: 16px;
  line-height: 1.75;
  color: var(--text-dark);
  background: var(--gray-bg);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

/* ---------- 英文模式排版微调 ----------
   中文字距对长英文词组过大，切换后收敛；字体改用西文栈 */
html[lang="en"] body { font-family: var(--font-en); }
html[lang="en"] .hero-title { font-size: clamp(42px, 7vw, 84px); letter-spacing: 2px; }
html[lang="en"] .hero-slogan { letter-spacing: 1px; }
html[lang="en"] .hero-sub { letter-spacing: .5px; }
html[lang="en"] .sec-title { letter-spacing: 0; }
html[lang="en"] .stat-label { font-size: 13px; letter-spacing: .3px; line-height: 1.5; }
html[lang="en"] .brand-cn { font-size: 16px; letter-spacing: 1px; }
html[lang="en"] .tab-btn { letter-spacing: .5px; }
html[lang="en"] .client-item { letter-spacing: 1px; }
html[lang="en"] .footer-staff-title { letter-spacing: 1px; }
html[lang="en"] .footer-staff-link { letter-spacing: .5px; }
html[lang="en"] .btn { letter-spacing: 1px; }

img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
ul, ol { list-style: none; }
button { font-family: inherit; cursor: pointer; border: none; background: none; }

h1, h2, h3, h4 { font-weight: 700; line-height: 1.3; }

section { scroll-margin-top: var(--nav-h); }

::selection { background: var(--gold); color: var(--navy-deep); }

/* ---------- 布局 ---------- */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 32px;
}

.section { padding: 110px 0; position: relative; }

/* ---------- 章节标题组件 ---------- */
.sec-head { margin-bottom: 64px; }
.sec-head.center { text-align: center; }

.sec-en {
  font-family: var(--font-en);
  font-size: 12px;
  letter-spacing: 5px;
  text-transform: uppercase;
  color: var(--blue-bright);
  margin-bottom: 14px;
}

.sec-line {
  width: 44px; height: 2px;
  background: var(--gold);
  margin-bottom: 18px;
}
.sec-head.center .sec-line { margin: 0 auto 18px; }

.sec-title {
  font-size: clamp(30px, 4vw, 46px);
  color: var(--navy);
  letter-spacing: 1px;
  margin-bottom: 12px;
}

.sec-sub {
  font-size: 16px;
  color: var(--text-gray);
  max-width: 720px;
}
.sec-head.center .sec-sub { margin: 0 auto; }

/* 深色板块上的标题组 */
.on-dark .sec-title { color: #fff; }
.on-dark .sec-sub { color: rgba(232, 238, 245, .72); }
.on-dark .sec-en { color: var(--gold); }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-block;
  position: relative;
  overflow: hidden;
  padding: 15px 38px;
  font-size: 15px;
  font-weight: 600;
  letter-spacing: 2px;
  border-radius: 4px;
  transition: transform .3s var(--ease), box-shadow .3s var(--ease), background .3s var(--ease), color .3s var(--ease), border-color .3s var(--ease);
}

.btn:active { transform: scale(.97); }

/* 主按钮：深蓝底白字 + 金色扫光 */
.btn-primary {
  background: var(--navy);
  color: #fff;
  border: 1px solid var(--navy);
}
.btn-primary:hover {
  background: var(--blue-bright);
  border-color: var(--blue-bright);
  box-shadow: 0 10px 26px rgba(30, 90, 168, .35);
}

/* 幽灵按钮：透明底金边白字（深色背景用） */
.btn-ghost {
  background: transparent;
  color: #fff;
  border: 1px solid var(--gold);
}
.btn-ghost:hover {
  background: rgba(201, 165, 76, .12);
  box-shadow: 0 10px 26px rgba(201, 165, 76, .25);
}

/* 金色扫光 */
.btn-primary::after, .btn-ghost::after {
  content: "";
  position: absolute;
  top: 0; left: -80%;
  width: 50%; height: 100%;
  background: linear-gradient(105deg, transparent, rgba(255, 255, 255, .35), transparent);
  transform: skewX(-20deg);
  transition: left .6s var(--ease);
}
.btn:hover::after { left: 130%; }

/* ---------- 入场动画 ---------- */
.reveal {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity .7s var(--ease), transform .7s var(--ease);
}
.reveal.in-view {
  opacity: 1;
  transform: none;
}

/* 动画降级：系统偏好减少动效 */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { transition: none; opacity: 1; transform: none; }
  *, *::before, *::after { animation-duration: .01s !important; animation-iteration-count: 1 !important; }
}