/* ============================================================
   Fanttik · 深圳范泰克科技创新有限公司
   品牌设计系统：黑 + 黄 + 白 ｜ 简约大气
   ============================================================ */

:root {
  --yellow: #FFC72C;
  --yellow-soft: #FFD96A;
  --black: #0A0A0A;
  --ink: #1A1A1A;
  --gray-900: #2A2A2A;
  --gray-700: #555;
  --gray-500: #888;
  --gray-300: #D5D5D5;
  --gray-100: #F4F4F4;
  --gray-50:  #FAFAFA;
  --white: #FFFFFF;

  --font-cn: "PingFang SC", "Microsoft YaHei", "HarmonyOS Sans SC", system-ui, sans-serif;
  --font-en: "Inter", "Helvetica Neue", system-ui, sans-serif;

  --max: 1200px;
  --pad: clamp(20px, 4vw, 48px);

  --shadow-soft: 0 18px 50px rgba(0,0,0,.12);
  --shadow-card: 0 24px 60px rgba(0,0,0,.18);
}

/* Reset */
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  font-family: var(--font-cn);
  color: var(--ink);
  background: var(--white);
  line-height: 1.7;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}
a { color: inherit; text-decoration: none; }
img { max-width: 100%; display: block; }
button { font: inherit; cursor: pointer; border: none; background: none; }
ul { list-style: none; }

/* ============================================================
   通用：章节标签（左上黄色书签）
   ============================================================ */
.section { padding: clamp(80px, 10vw, 140px) var(--pad); }
.section--dark { background: var(--black); color: var(--white); }
.section--light { background: var(--white); color: var(--ink); }
.section--soft  { background: var(--gray-50); }

.container { max-width: var(--max); margin: 0 auto; }

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 14px;
  margin-bottom: 24px;
}
.eyebrow__tab {
  width: 10px; height: 32px;
  background: var(--yellow);
  border-radius: 1px;
  flex-shrink: 0;
}
.eyebrow__cn {
  font-size: 22px;
  font-weight: 700;
  letter-spacing: 4px;
}
.eyebrow__en {
  font-size: 12px;
  letter-spacing: 3px;
  color: var(--gray-500);
  font-family: var(--font-en);
  font-weight: 600;
  text-transform: uppercase;
}
.section--dark .eyebrow__en { color: var(--gray-500); }

.section-title {
  font-size: clamp(34px, 4.4vw, 54px);
  font-weight: 800;
  line-height: 1.25;
  letter-spacing: 1px;
  margin-bottom: 18px;
}
.section-sub {
  font-size: clamp(16px, 1.4vw, 19px);
  color: var(--gray-700);
  max-width: 780px;
  line-height: 1.85;
}
.section--dark .section-sub { color: rgba(255,255,255,.7); }

.section-head { margin-bottom: 64px; max-width: 880px; }

/* ============================================================
   导航栏
   ============================================================ */
.nav {
  position: fixed; top: 0; left: 0; right: 0;
  z-index: 100;
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px var(--pad);
  background: rgba(10,10,10,.0);
  transition: background .35s ease, backdrop-filter .35s ease, border-color .35s ease;
  border-bottom: 1px solid transparent;
}
.nav.is-scrolled,
.nav.is-dark {
  background: rgba(10,10,10,.78);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom-color: rgba(255,255,255,.08);
}
.nav__logo {
  display: flex; align-items: center; gap: 10px;
  font-family: var(--font-en);
  font-size: 26px; font-weight: 800;
  color: var(--white);
  letter-spacing: -0.5px;
}
.nav__logo-mark {
  width: 8px; height: 26px;
  background: var(--yellow);
  border-radius: 1px;
}
.nav__menu { display: flex; gap: 36px; align-items: center; }
.nav__link {
  position: relative;
  color: var(--white);
  font-size: 15px;
  font-weight: 500;
  padding: 6px 2px;
  transition: color .25s ease;
}
.nav__link::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -2px;
  height: 2px; background: var(--yellow);
  transform: scaleX(0); transform-origin: left;
  transition: transform .3s ease;
}
.nav__link:hover { color: var(--yellow); }
.nav__link:hover::after,
.nav__link.is-active::after { transform: scaleX(1); }
.nav__cta {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 10px 18px;
  background: var(--yellow);
  color: var(--black);
  font-size: 14px; font-weight: 700;
  border-radius: 2px;
  transition: transform .25s ease, background .25s ease;
}
.nav__cta:hover { background: var(--white); transform: translateY(-1px); }
.nav__toggle { display: none; }

/* 移动端菜单 */
@media (max-width: 860px) {
  .nav__menu {
    position: fixed; top: 0; right: 0; bottom: 0;
    width: min(82vw, 360px);
    flex-direction: column; align-items: flex-start;
    padding: 96px 32px 40px;
    background: var(--black);
    transform: translateX(100%);
    transition: transform .35s ease;
    border-left: 1px solid rgba(255,255,255,.06);
  }
  .nav__menu.is-open { transform: translateX(0); }
  .nav__link { font-size: 22px; }
  .nav__toggle {
    display: flex; flex-direction: column; gap: 5px;
    width: 32px; height: 32px; align-items: center; justify-content: center;
  }
  .nav__toggle span {
    display: block; width: 22px; height: 2px;
    background: var(--white); border-radius: 1px;
    transition: transform .3s ease, opacity .3s ease;
  }
  .nav.is-open .nav__toggle span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
  .nav.is-open .nav__toggle span:nth-child(2) { opacity: 0; }
  .nav.is-open .nav__toggle span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }
}

/* ============================================================
   按钮
   ============================================================ */
.btn {
  display: inline-flex; align-items: center; gap: 10px;
  padding: 14px 28px;
  font-size: 15px; font-weight: 700;
  border-radius: 2px;
  transition: transform .25s ease, background .25s ease, color .25s ease, box-shadow .25s ease;
}
.btn--primary { background: var(--yellow); color: var(--black); }
.btn--primary:hover { background: var(--white); transform: translateY(-2px); box-shadow: var(--shadow-soft); }
.btn--ghost { background: transparent; color: var(--white); border: 1.5px solid rgba(255,255,255,.4); }
.btn--ghost:hover { background: var(--white); color: var(--black); border-color: var(--white); }
.btn--ink { background: var(--black); color: var(--white); }
.btn--ink:hover { background: var(--yellow); color: var(--black); }
.btn .arrow { transition: transform .25s ease; }
.btn:hover .arrow { transform: translateX(4px); }

/* ============================================================
   页脚
   ============================================================ */
.footer {
  background: var(--black);
  color: rgba(255,255,255,.65);
  padding: 80px var(--pad) 32px;
}
.footer__grid {
  max-width: var(--max); margin: 0 auto;
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr 1fr;
  gap: 56px;
  padding-bottom: 56px;
  border-bottom: 1px solid rgba(255,255,255,.08);
}
.footer__brand .nav__logo { margin-bottom: 18px; }
.footer__brand p { font-size: 14px; line-height: 1.85; max-width: 340px; }
.footer__col h4 {
  color: var(--white); font-size: 15px; font-weight: 700;
  margin-bottom: 18px; letter-spacing: 1px;
}
.footer__col ul li { margin-bottom: 10px; }
.footer__col a { font-size: 14px; transition: color .25s ease; }
.footer__col a:hover { color: var(--yellow); }
.footer__bottom {
  max-width: var(--max); margin: 24px auto 0;
  display: flex; justify-content: space-between; align-items: center;
  font-size: 12px; letter-spacing: 1px; flex-wrap: wrap; gap: 12px;
}
.footer__social { display: flex; gap: 14px; }
.footer__social a {
  width: 36px; height: 36px;
  display: inline-flex; align-items: center; justify-content: center;
  background: rgba(255,255,255,.06);
  border-radius: 50%;
  transition: background .25s ease, color .25s ease, transform .25s ease;
  color: var(--white);
}
.footer__social a:hover { background: var(--yellow); color: var(--black); transform: translateY(-2px); }
@media (max-width: 860px) {
  .footer__grid { grid-template-columns: 1fr 1fr; gap: 40px; }
  .footer__brand { grid-column: 1 / -1; }
}
@media (max-width: 540px) {
  .footer__grid { grid-template-columns: 1fr; }
}

/* ============================================================
   通用工具类
   ============================================================ */
.fade-up {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity .8s ease, transform .8s ease;
}
.fade-up.in {
  opacity: 1; transform: none;
}

.slogan-line {
  display: inline-flex; align-items: center; gap: 14px;
  font-family: var(--font-en);
  font-style: italic;
  font-size: 18px;
  color: var(--yellow);
  letter-spacing: .5px;
}
.slogan-line::before,
.slogan-line::after {
  content: "—";
  color: var(--yellow);
  opacity: .8;
}

/* 黑色背景下的 slogan */
.section--dark .slogan-line { color: var(--white); }
.section--dark .slogan-line::before,
.section--dark .slogan-line::after { color: var(--yellow); }

/* ============================================================
   响应式
   ============================================================ */
@media (max-width: 768px) {
  .section { padding: 80px 20px; }
  .section-head { margin-bottom: 48px; }
}