/* ============================================================
   大夏龙腾 · 备案精简版主页样式（正式企业风）
   直角、克制配色、无花哨动效
   ============================================================ */

:root {
  --navy: #0D1B2A;
  --navy-mid: #1B2D45;
  --gold: #C8A24B;
  --gold-deep: #A9862F;
  --gold-light: #D4B76A;
  --paper: #F5F2EB;
  --paper-bright: #FAF8F3;
  --ink: #222222;
  --ink-mid: #4A4A4A;
  --ink-muted: #6B6B6B;
  --white: #FFFFFF;
  --line: rgba(13, 27, 42, .16);
  --line-light: rgba(255, 255, 255, .18);
  --font-display: "Songti SC", "Noto Serif SC", "SimSun", "Source Han Serif SC", serif;
  --font-body: "PingFang SC", "Microsoft YaHei", "Hiragino Sans GB", "Noto Sans SC", sans-serif;
  --nav-h: 64px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  color: var(--ink);
  background: var(--paper);
  line-height: 1.7;
  overflow-x: hidden;
}

img { max-width: 100%; display: block; }
a { text-decoration: none; color: inherit; }
ul { list-style: none; }

.container { width: min(1120px, 92%); margin: 0 auto; }

/* ---------- 顶部导航（纯色，无透明模糊） ---------- */
.nav {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 100;
  height: var(--nav-h);
  background: var(--navy);
  border-bottom: 1px solid var(--line-light);
}
.nav-inner {
  width: min(1120px, 92%);
  height: 100%;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.nav-brand { display: flex; align-items: center; gap: 10px; }
.nav-logo { width: 28px; height: 28px; }
.nav-brand-text { display: flex; flex-direction: column; line-height: 1.2; }
.brand-mark { font-family: var(--font-display); font-size: 1.15rem; font-weight: 900; color: var(--gold); letter-spacing: .08em; }
.brand-sub { font-size: .56rem; color: rgba(255, 255, 255, .55); letter-spacing: .24em; }

.nav-links { display: flex; align-items: center; gap: 34px; }
.nav-links a {
  position: relative;
  font-size: .92rem;
  color: rgba(255, 255, 255, .85);
  padding: 8px 2px;
  border-bottom: 2px solid transparent;
  transition: color .2s, border-color .2s;
}
.nav-links a:hover, .nav-links a.nav-active { color: var(--gold-light); border-bottom-color: var(--gold); }
.nav-links a.nav-cta {
  padding: 8px 20px;
  border: 1px solid var(--gold);
  border-bottom: 1px solid var(--gold);
  color: var(--gold-light);
}
.nav-links a.nav-cta:hover { background: var(--gold); color: var(--navy); }

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 40px; height: 40px;
  background: none;
  border: 1px solid var(--line-light);
  cursor: pointer;
  padding: 10px;
}
.nav-toggle span { display: block; height: 2px; width: 100%; background: var(--gold-light); }
.nav-toggle.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.open span:nth-child(2) { opacity: 0; }
.nav-toggle.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ---------- 首页横幅 ---------- */
.hero {
  position: relative;
  padding: 150px 0 70px;
  color: var(--white);
  text-align: center;
  overflow: hidden;
}
.hero-bg, .hero-bg img { position: absolute; inset: 0; width: 100%; height: 100%; }
.hero-bg img { object-fit: cover; }
.hero-overlay { position: absolute; inset: 0; background: rgba(13, 27, 42, .86); }

.hero-content { position: relative; z-index: 2; width: min(820px, 90%); margin: 0 auto; }
.hero-brand-block { margin-bottom: 16px; }
.hero-company {
  font-family: var(--font-display);
  font-size: clamp(2.4rem, 6vw, 4rem);
  font-weight: 900;
  letter-spacing: .1em;
  line-height: 1.2;
}
.hero-company-full {
  font-family: var(--font-display);
  font-size: clamp(1rem, 2.2vw, 1.25rem);
  letter-spacing: .34em;
  color: rgba(255, 255, 255, .85);
  margin-top: 6px;
}
.hero-slogan {
  font-family: var(--font-display);
  font-size: clamp(1.05rem, 2.4vw, 1.35rem);
  color: var(--gold);
  letter-spacing: .14em;
  margin: 18px 0 12px;
}
.hero-desc {
  max-width: 640px;
  margin: 0 auto;
  font-size: 1rem;
  color: rgba(255, 255, 255, .82);
}
.hero-actions { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; margin-top: 32px; }

.btn {
  display: inline-block;
  padding: 12px 30px;
  border: 1px solid transparent;
  font-size: .95rem;
  font-weight: 600;
  letter-spacing: .05em;
  transition: background .2s, color .2s, border-color .2s;
}
.btn-primary { background: var(--gold); color: var(--navy); }
.btn-primary:hover { background: var(--gold-deep); color: var(--white); }
.btn-outline { border-color: rgba(255, 255, 255, .6); color: var(--white); }
.btn-outline:hover { background: rgba(255, 255, 255, .1); border-color: var(--white); }

/* ---------- 通用区块 ---------- */
.section { padding: 76px 0; }
.section-about { background: var(--paper); }
.section-business { background: var(--white); }
.section-cases { background: var(--paper); }
.section-contact { background: var(--white); }

.section-eyebrow {
  font-size: .76rem;
  font-weight: 600;
  letter-spacing: .2em;
  color: var(--gold-deep);
  margin-bottom: 10px;
}
.section-title {
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  font-weight: 900;
  color: var(--navy);
  letter-spacing: .05em;
  padding-bottom: 14px;
  margin-bottom: 30px;
  position: relative;
}
.section-title::after {
  content: "";
  position: absolute;
  left: 0; bottom: 0;
  width: 56px; height: 3px;
  background: var(--gold);
}
.section-desc { color: var(--ink-muted); max-width: 640px; margin-bottom: 34px; }

/* ---------- 企业简介 ---------- */
.about-grid {
  display: grid;
  grid-template-columns: 1.15fr .85fr;
  gap: 44px;
  align-items: start;
}
.about-text p { color: var(--ink-mid); margin-bottom: 14px; }
.about-text strong { color: var(--navy); }
.about-facts { border: 1px solid var(--line); background: var(--paper-bright); }
.fact-row { padding: 16px 20px; border-bottom: 1px solid var(--line); }
.fact-row:last-child { border-bottom: none; }
.fact-label {
  display: block;
  font-size: .72rem;
  letter-spacing: .14em;
  color: var(--gold-deep);
  margin-bottom: 4px;
}
.fact-value { font-size: .93rem; color: var(--ink); }

/* ---------- 核心业务 ---------- */
.biz-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
}
.biz-card {
  background: var(--white);
  border: 1px solid var(--line);
  border-top: 3px solid var(--navy-mid);
  padding: 26px 22px 24px;
  transition: border-color .2s;
}
.biz-card:hover { border-color: var(--gold); border-top-color: var(--gold); }
.biz-num { font-size: .78rem; font-weight: 700; letter-spacing: .12em; color: var(--gold-deep); }
.biz-card h3 { font-family: var(--font-display); font-size: 1.15rem; color: var(--navy); margin: 10px 0 8px; }
.biz-card p { font-size: .9rem; color: var(--ink-mid); }

/* ---------- 典型案例 ---------- */
.case-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  align-items: start;
}
.case-card {
  background: var(--white);
  border: 1px solid var(--line);
  cursor: pointer;
  transition: border-color .2s;
}
.case-card:hover { border-color: var(--gold); }
.case-cover { position: relative; height: 185px; overflow: hidden; }
.case-cover img { width: 100%; height: 100%; object-fit: cover; }
.case-tag {
  position: absolute;
  top: 12px; left: 12px;
  background: rgba(13, 27, 42, .85);
  color: var(--gold-light);
  font-size: .74rem;
  letter-spacing: .08em;
  padding: 4px 10px;
  border: 1px solid rgba(200, 162, 75, .5);
}
.case-body { padding: 20px 20px 18px; }
.case-body h3 { font-family: var(--font-display); font-size: 1.08rem; color: var(--navy); margin-bottom: 6px; }
.case-summary { font-size: .88rem; color: var(--ink-mid); }
.case-more {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 12px;
  font-size: .84rem;
  font-weight: 600;
  color: var(--gold-deep);
}
.case-card.open .case-more .arrow { transform: rotate(180deg); }
.case-more .arrow { display: inline-block; transition: transform .2s; }

.case-detail {
  max-height: 0;
  overflow: hidden;
  border-top: 1px solid var(--line);
  transition: max-height .45s;
}
.case-card.open .case-detail { max-height: 640px; }
.case-detail-inner { padding: 18px 20px 22px; }
.case-lead { font-size: .9rem; color: var(--ink-mid); margin-bottom: 14px; }
.case-meta { display: grid; grid-template-columns: 1fr 1fr; gap: 10px 16px; margin-bottom: 14px; }
.meta-item { display: flex; flex-direction: column; gap: 2px; }
.meta-label { font-size: .68rem; letter-spacing: .1em; color: var(--gold-deep); }
.meta-value { font-size: .86rem; color: var(--ink); }
.case-services { display: flex; flex-wrap: wrap; gap: 8px; }
.case-services span {
  font-size: .78rem;
  color: var(--navy);
  border: 1px solid rgba(200, 162, 75, .5);
  background: var(--paper-bright);
  padding: 3px 10px;
}

/* ---------- 联系方式 ---------- */
.contact-info {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
.contact-item {
  border: 1px solid var(--line);
  background: var(--paper-bright);
  padding: 20px 22px;
}
.contact-label {
  display: block;
  font-size: .72rem;
  letter-spacing: .14em;
  color: var(--gold-deep);
  margin-bottom: 6px;
}
.contact-item a, .contact-item span { font-size: .92rem; color: var(--ink); word-break: break-all; }
.contact-item a:hover { color: var(--gold-deep); }

/* ---------- 页脚 ---------- */
.footer { background: var(--navy); color: rgba(255, 255, 255, .72); border-top: 4px solid var(--gold); }
.footer-inner {
  width: min(1120px, 92%);
  margin: 0 auto;
  padding: 44px 0 34px;
  display: grid;
  grid-template-columns: 1.4fr 1fr 1fr;
  gap: 40px;
}
.footer-brand .brand-mark { font-size: 1.25rem; }
.footer-company { color: var(--white); font-size: .95rem; margin: 12px 0 6px; }
.footer-addr { font-size: .82rem; color: rgba(255, 255, 255, .55); line-height: 1.8; }
.footer-col { display: flex; flex-direction: column; gap: 10px; }
.footer-col h5 {
  font-family: var(--font-display);
  font-size: .95rem;
  color: var(--gold);
  letter-spacing: .1em;
  margin-bottom: 4px;
}
.footer-col a, .footer-col span { font-size: .86rem; color: rgba(255, 255, 255, .62); }
.footer-col a:hover { color: var(--gold-light); }
.footer-bottom {
  border-top: 1px solid var(--line-light);
  padding: 18px 0;
  text-align: center;
  font-size: .78rem;
  color: rgba(255, 255, 255, .5);
  letter-spacing: .04em;
}
.footer-bottom p + p { margin-top: 4px; }

/* ---------- 响应式 ---------- */
@media (max-width: 960px) {
  .biz-grid { grid-template-columns: repeat(2, 1fr); }
  .case-grid { grid-template-columns: 1fr; max-width: 620px; margin: 0 auto; }
  .about-grid { grid-template-columns: 1fr; }
  .contact-info { grid-template-columns: 1fr; }
  .footer-inner { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 640px) {
  .section { padding: 60px 0; }
  .nav-toggle { display: flex; }
  .nav-links {
    position: fixed;
    top: var(--nav-h);
    left: 0; right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--navy);
    border-bottom: 1px solid var(--line-light);
    padding: 10px 8%;
    transform: translateY(-8px);
    opacity: 0;
    visibility: hidden;
    transition: transform .3s, opacity .3s, visibility .3s;
  }
  .nav-links.open { transform: none; opacity: 1; visibility: visible; }
  .nav-links a { display: block; padding: 14px 4px; border-bottom: 1px solid var(--line-light); border-bottom-color: var(--line-light); }
  .nav-links a.nav-cta { margin-top: 12px; text-align: center; border: 1px solid var(--gold); }
  .hero { padding: 120px 0 56px; }
  .hero-actions { flex-direction: column; align-items: center; }
  .btn { width: min(280px, 100%); text-align: center; }
  .biz-grid { grid-template-columns: 1fr; }
  .footer-inner { grid-template-columns: 1fr; gap: 26px; }
}
/* ---------- 首页横幅内 logo ---------- */
/* ---------- 白底图标（导航 + 首页横幅） ---------- */
.nav-logo {
  width: 30px;
  height: 30px;
  padding: 3px;
  background: #FFFFFF;
  border: 1px solid rgba(255, 255, 255, .25);
}

/* ---------- 企业简介（单栏）+ 联系方式布局 ---------- */
.about-grid { grid-template-columns: 1fr; }
.about-text { max-width: 760px; }
.contact-info { grid-template-columns: repeat(2, 1fr); }
.contact-subtitle {
  font-size: .76rem;
  font-weight: 600;
  letter-spacing: .18em;
  color: var(--gold-deep);
  margin: 30px 0 10px;
}
.contact-facts { max-width: 760px; }

/* ---------- 案例详情图片画廊 ---------- */
.case-card.open .case-detail { max-height: 900px; }
.case-gallery { margin-top: 4px; }
.gallery-label {
  display: block;
  font-size: .68rem;
  letter-spacing: .1em;
  color: var(--gold-deep);
  margin: 16px 0 8px;
}
.gallery-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}
.gallery-grid img {
  width: 100%;
  height: 120px;
  object-fit: cover;
  border: 1px solid var(--line);
}