/* ============================================
   yejinwuliu.cn — 冶金智能运输技术中心
   设计风格：深蓝钢铁色 + 亮橙点缀，工业科技感
   ============================================ */

:root {
  --steel-900: #0A1628;
  --steel-800: #0F2035;
  --steel-700: #162D4A;
  --steel-600: #1E3A5F;
  --steel-500: #2A4D73;
  --steel-400: #3D6B94;
  --steel-300: #5A8AB5;
  --steel-200: #89B0D0;
  --steel-100: #B8D4E8;
  --steel-50:  #E3EFF7;

  --orange-600: #E8600A;
  --orange-500: #FF6B1A;
  --orange-400: #FF8A40;
  --orange-300: #FFAA6B;
  --orange-200: #FFC89E;
  --orange-100: #FFE4CC;

  --white: #FFFFFF;
  --gray-100: #F5F7FA;
  --gray-200: #E8ECF0;
  --gray-300: #CDD4DB;
  --gray-400: #9AA5B0;
  --gray-500: #6B7A8A;
  --gray-600: #4A5568;
  --gray-700: #2D3748;
  --gray-800: #1A202C;

  --font-sans: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-display: 'Noto Sans SC', sans-serif;

  --container: 1200px;
  --radius: 8px;
  --radius-lg: 16px;
  --shadow: 0 4px 24px rgba(10, 22, 40, 0.15);
  --shadow-lg: 0 8px 40px rgba(10, 22, 40, 0.25);

  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html { scroll-behavior: smooth; font-size: 16px; }

body {
  font-family: var(--font-sans);
  color: var(--gray-700);
  background: var(--white);
  line-height: 1.7;
  overflow-x: hidden;
}

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

/* Container */
.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
}

/* ============ Navigation ============ */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(10, 22, 40, 0.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  transition: var(--transition);
}

.nav.scrolled {
  background: rgba(10, 22, 40, 0.98);
  box-shadow: 0 2px 20px rgba(0, 0, 0, 0.3);
}

.nav-inner {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 12px;
}

.nav-logo-icon {
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--orange-500), var(--orange-400));
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 18px;
  color: var(--white);
}

.nav-logo-text {
  color: var(--white);
  font-size: 18px;
  font-weight: 600;
  letter-spacing: 1px;
}

.nav-logo-text span {
  color: var(--orange-400);
  font-size: 12px;
  display: block;
  font-weight: 400;
  letter-spacing: 2px;
  margin-top: -2px;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-links a {
  color: rgba(255, 255, 255, 0.7);
  font-size: 14px;
  font-weight: 400;
  padding: 8px 16px;
  border-radius: 6px;
  transition: var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--white);
  background: rgba(255, 255, 255, 0.08);
}

.nav-links a.active {
  color: var(--orange-400);
}

/* Mobile Menu Toggle */
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}

.nav-toggle span {
  width: 24px;
  height: 2px;
  background: var(--white);
  border-radius: 2px;
  transition: var(--transition);
}

/* ============ Hero Section ============ */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  background: var(--steel-900);
  overflow: hidden;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 80% 60% at 70% 40%, rgba(232, 96, 10, 0.12) 0%, transparent 60%),
    radial-gradient(ellipse 60% 80% at 20% 80%, rgba(30, 58, 95, 0.6) 0%, transparent 60%),
    linear-gradient(180deg, var(--steel-900) 0%, var(--steel-800) 100%);
}

.hero-grid {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.02) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.02) 1px, transparent 1px);
  background-size: 60px 60px;
  mask-image: radial-gradient(ellipse 70% 50% at 50% 50%, black 30%, transparent 80%);
}

.hero-particles {
  position: absolute;
  inset: 0;
}

.hero-particle {
  position: absolute;
  width: 3px;
  height: 3px;
  background: var(--orange-400);
  border-radius: 50%;
  opacity: 0;
  animation: particle-float 8s infinite;
}

@keyframes particle-float {
  0% { opacity: 0; transform: translateY(100vh) scale(0); }
  10% { opacity: 0.6; }
  90% { opacity: 0.6; }
  100% { opacity: 0; transform: translateY(-10vh) scale(1); }
}

.hero-content {
  position: relative;
  max-width: var(--container);
  margin: 0 auto;
  padding: 120px 24px 80px;
  width: 100%;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: rgba(255, 107, 26, 0.1);
  border: 1px solid rgba(255, 107, 26, 0.25);
  border-radius: 24px;
  padding: 6px 18px;
  font-size: 13px;
  color: var(--orange-300);
  margin-bottom: 28px;
  animation: fade-in-up 0.8s ease-out;
}

.hero-badge::before {
  content: '';
  width: 6px;
  height: 6px;
  background: var(--orange-500);
  border-radius: 50%;
  animation: pulse-dot 2s infinite;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.5; transform: scale(1.5); }
}

.hero h1 {
  font-size: clamp(36px, 5vw, 64px);
  font-weight: 700;
  color: var(--white);
  line-height: 1.15;
  margin-bottom: 24px;
  animation: fade-in-up 0.8s ease-out 0.15s both;
}

.hero h1 .highlight {
  background: linear-gradient(135deg, var(--orange-400), var(--orange-500));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-subtitle {
  font-size: clamp(16px, 2vw, 20px);
  color: rgba(255, 255, 255, 0.6);
  max-width: 600px;
  line-height: 1.8;
  margin-bottom: 40px;
  animation: fade-in-up 0.8s ease-out 0.3s both;
}

.hero-actions {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  animation: fade-in-up 0.8s ease-out 0.45s both;
}

@keyframes fade-in-up {
  from { opacity: 0; transform: translateY(24px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 32px;
  border-radius: var(--radius);
  font-size: 15px;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
  border: none;
  font-family: var(--font-sans);
}

.btn-primary {
  background: linear-gradient(135deg, var(--orange-500), var(--orange-400));
  color: var(--white);
  box-shadow: 0 4px 16px rgba(255, 107, 26, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 24px rgba(255, 107, 26, 0.4);
}

.btn-outline {
  background: transparent;
  color: rgba(255, 255, 255, 0.8);
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.btn-outline:hover {
  background: rgba(255, 255, 255, 0.06);
  border-color: rgba(255, 255, 255, 0.35);
  color: var(--white);
}

/* Hero Stats */
.hero-stats {
  display: flex;
  gap: 48px;
  margin-top: 64px;
  padding-top: 32px;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  animation: fade-in-up 0.8s ease-out 0.6s both;
}

.hero-stat-value {
  font-size: 36px;
  font-weight: 700;
  color: var(--white);
  font-variant-numeric: tabular-nums;
}

.hero-stat-value .unit {
  font-size: 18px;
  color: var(--orange-400);
  font-weight: 500;
}

.hero-stat-label {
  font-size: 13px;
  color: rgba(255, 255, 255, 0.45);
  margin-top: 4px;
}

/* ============ Section Base ============ */
.section {
  padding: 100px 0;
}

.section-header {
  text-align: center;
  margin-bottom: 64px;
}

.section-tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  font-weight: 500;
  color: var(--orange-500);
  text-transform: uppercase;
  letter-spacing: 3px;
  margin-bottom: 16px;
}

.section-tag::before {
  content: '';
  width: 20px;
  height: 2px;
  background: var(--orange-500);
}

.section-title {
  font-size: clamp(28px, 3.5vw, 40px);
  font-weight: 700;
  color: var(--steel-900);
  line-height: 1.2;
  margin-bottom: 16px;
}

.section-desc {
  font-size: 16px;
  color: var(--gray-500);
  max-width: 640px;
  margin: 0 auto;
  line-height: 1.8;
}

/* ============ Tech Section ============ */
.tech-section {
  background: var(--gray-100);
}

.tech-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 24px;
}

.tech-card {
  background: var(--white);
  border-radius: var(--radius-lg);
  padding: 36px;
  transition: var(--transition);
  border: 1px solid var(--gray-200);
  position: relative;
  overflow: hidden;
}

.tech-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--orange-500), var(--steel-400));
  opacity: 0;
  transition: var(--transition);
}

.tech-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: transparent;
}

.tech-card:hover::before {
  opacity: 1;
}

.tech-icon {
  width: 56px;
  height: 56px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
  margin-bottom: 20px;
}

.tech-icon.t1 { background: rgba(232, 96, 10, 0.1); color: var(--orange-500); }
.tech-icon.t2 { background: rgba(42, 77, 115, 0.1); color: var(--steel-500); }
.tech-icon.t3 { background: rgba(99, 153, 34, 0.1); color: #639922; }
.tech-icon.t4 { background: rgba(212, 83, 126, 0.1); color: #D4537E; }
.tech-icon.t5 { background: rgba(127, 119, 221, 0.1); color: #7F77DD; }

.tech-card h3 {
  font-size: 20px;
  font-weight: 600;
  color: var(--steel-900);
  margin-bottom: 12px;
}

.tech-card p {
  font-size: 14px;
  color: var(--gray-500);
  line-height: 1.8;
}

.tech-tag {
  display: inline-block;
  font-size: 11px;
  padding: 4px 10px;
  border-radius: 4px;
  background: var(--gray-100);
  color: var(--gray-600);
  margin-top: 16px;
  margin-right: 6px;
}

/* ============ Data Highlights ============ */
.data-section {
  background: var(--steel-900);
  color: var(--white);
  position: relative;
  overflow: hidden;
}

.data-section::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(255, 107, 26, 0.08) 0%, transparent 60%);
  pointer-events: none;
}

.data-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 32px;
  position: relative;
}

.data-item {
  text-align: center;
  padding: 40px 20px;
}

.data-value {
  font-size: 48px;
  font-weight: 700;
  color: var(--white);
  font-variant-numeric: tabular-nums;
  line-height: 1;
}

.data-value .accent {
  color: var(--orange-400);
}

.data-label {
  font-size: 14px;
  color: rgba(255, 255, 255, 0.5);
  margin-top: 12px;
}

.data-desc {
  font-size: 12px;
  color: rgba(255, 255, 255, 0.3);
  margin-top: 4px;
}

/* ============ Projects Section ============ */
.project-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
}

.project-card {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  overflow: hidden;
  transition: var(--transition);
}

.project-card:hover {
  box-shadow: var(--shadow);
  border-color: transparent;
  transform: translateY(-2px);
}

.project-thumb {
  height: 180px;
  background: var(--steel-800);
  position: relative;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
}

.project-thumb-text {
  color: rgba(255, 255, 255, 0.6);
  font-size: 14px;
  text-align: center;
  padding: 20px;
}

.project-thumb .overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, transparent 40%, rgba(10, 22, 40, 0.7) 100%);
}

.project-info {
  padding: 20px;
}

.project-info h4 {
  font-size: 16px;
  font-weight: 600;
  color: var(--steel-900);
  margin-bottom: 6px;
}

.project-info p {
  font-size: 13px;
  color: var(--gray-500);
  line-height: 1.6;
}

.project-tag {
  display: inline-block;
  font-size: 11px;
  padding: 3px 8px;
  border-radius: 4px;
  margin-top: 10px;
  margin-right: 4px;
}

.project-tag.steel { background: #E6F1FB; color: #185FA5; }
.project-tag.capacitor { background: #EAF3DE; color: #3B6D11; }
.project-tag.ladle { background: #FBEAF0; color: #993556; }
.project-tag.torpedo { background: #EEEDFE; color: #534AB7; }

/* ============ Timeline (About Page) ============ */
.timeline {
  position: relative;
  max-width: 800px;
  margin: 0 auto;
  padding: 20px 0;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 50%;
  top: 0;
  bottom: 0;
  width: 2px;
  background: var(--gray-200);
  transform: translateX(-50%);
}

.timeline-item {
  display: flex;
  align-items: flex-start;
  margin-bottom: 48px;
  position: relative;
}

.timeline-item:nth-child(odd) {
  flex-direction: row-reverse;
  text-align: right;
}

.timeline-dot {
  position: absolute;
  left: 50%;
  top: 8px;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--orange-500);
  border: 3px solid var(--white);
  box-shadow: 0 0 0 3px rgba(255, 107, 26, 0.2);
  transform: translateX(-50%);
  z-index: 1;
}

.timeline-content {
  width: calc(50% - 40px);
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  padding: 24px;
}

.timeline-year {
  font-size: 14px;
  font-weight: 600;
  color: var(--orange-500);
  margin-bottom: 6px;
}

.timeline-content h4 {
  font-size: 16px;
  font-weight: 600;
  color: var(--steel-900);
  margin-bottom: 8px;
}

.timeline-content p {
  font-size: 13px;
  color: var(--gray-500);
  line-height: 1.7;
}

/* ============ CTA Section ============ */
.cta-section {
  background: linear-gradient(135deg, var(--steel-800), var(--steel-700));
  color: var(--white);
  text-align: center;
  padding: 80px 0;
  position: relative;
  overflow: hidden;
}

.cta-section::before {
  content: '';
  position: absolute;
  top: -100px;
  right: -100px;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(255, 107, 26, 0.1) 0%, transparent 60%);
}

.cta-section h2 {
  font-size: 32px;
  font-weight: 700;
  margin-bottom: 16px;
}

.cta-section p {
  font-size: 16px;
  color: rgba(255, 255, 255, 0.6);
  max-width: 500px;
  margin: 0 auto 32px;
}

/* ============ Footer ============ */
.footer {
  background: var(--steel-900);
  color: rgba(255, 255, 255, 0.5);
  padding: 64px 0 32px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand h3 {
  color: var(--white);
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 12px;
}

.footer-brand p {
  font-size: 13px;
  line-height: 1.8;
  max-width: 300px;
}

.footer-col h4 {
  color: rgba(255, 255, 255, 0.8);
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 16px;
}

.footer-col a {
  display: block;
  font-size: 13px;
  padding: 4px 0;
  transition: var(--transition);
}

.footer-col a:hover {
  color: var(--orange-400);
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.06);
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 12px;
}

.footer-icp a {
  color: rgba(255, 255, 255, 0.4);
  transition: var(--transition);
}

.footer-icp a:hover {
  color: var(--orange-400);
}

/* ============ Page Header (Inner Pages) ============ */
.page-header {
  background: var(--steel-900);
  padding: 140px 0 80px;
  position: relative;
  overflow: hidden;
}

.page-header::before {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(ellipse 80% 50% at 60% 50%, rgba(232, 96, 10, 0.08) 0%, transparent 60%);
}

.page-header h1 {
  font-size: 40px;
  font-weight: 700;
  color: var(--white);
  margin-bottom: 12px;
  position: relative;
}

.page-header p {
  font-size: 16px;
  color: rgba(255, 255, 255, 0.5);
  position: relative;
}

/* ============ Content Pages ============ */
.content-section {
  padding: 80px 0;
}

.content-section h2 {
  font-size: 28px;
  font-weight: 600;
  color: var(--steel-900);
  margin-bottom: 16px;
}

.content-section h3 {
  font-size: 20px;
  font-weight: 600;
  color: var(--steel-800);
  margin-bottom: 12px;
}

.content-section p {
  font-size: 15px;
  color: var(--gray-600);
  line-height: 1.8;
  margin-bottom: 16px;
}

/* ============ Contact Page ============ */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
}

.contact-card {
  background: var(--white);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-lg);
  padding: 36px;
}

.contact-item {
  display: flex;
  gap: 16px;
  margin-bottom: 24px;
}

.contact-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  background: rgba(232, 96, 10, 0.08);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--orange-500);
  font-size: 20px;
  flex-shrink: 0;
}

.contact-item h4 {
  font-size: 14px;
  font-weight: 600;
  color: var(--steel-900);
  margin-bottom: 4px;
}

.contact-item p {
  font-size: 14px;
  color: var(--gray-500);
}

/* ============ Responsive ============ */
@media (max-width: 1024px) {
  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }

  .data-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  .nav-links { display: none; }
  .nav-toggle { display: flex; }

  .nav-links.open {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 72px;
    left: 0;
    right: 0;
    background: rgba(10, 22, 40, 0.98);
    padding: 16px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.06);
  }

  .hero-stats {
    flex-wrap: wrap;
    gap: 24px;
  }

  .hero-stat { min-width: 45%; }

  .data-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
  }

  .data-value { font-size: 32px; }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 24px;
  }

  .contact-grid {
    grid-template-columns: 1fr;
  }

  .timeline::before { left: 20px; }
  .timeline-dot { left: 20px; }
  .timeline-item,
  .timeline-item:nth-child(odd) {
    flex-direction: row;
    text-align: left;
  }
  .timeline-content { width: calc(100% - 60px); margin-left: 50px; }
}

@media (max-width: 480px) {
  .hero h1 { font-size: 28px; }
  .hero-subtitle { font-size: 15px; }
  .hero-actions { flex-direction: column; }
  .btn { width: 100%; justify-content: center; }
  .data-grid { grid-template-columns: 1fr; }
  .tech-grid { grid-template-columns: 1fr; }
}