/* ===== CSS Variables ===== */
:root {
  --color-primary: #1a3a5c;
  --color-primary-light: #2a5a8c;
  --color-accent: #0077b6;
  --color-accent-light: #00b4d8;
  --color-bg: #ffffff;
  --color-bg-alt: #f5f7fa;
  --color-bg-dark: #0f2133;
  --color-text: #333333;
  --color-text-light: #666666;
  --color-text-muted: #999999;
  --color-border: #e0e4e8;
  --color-white: #ffffff;
  --font-family: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --max-width: 1200px;
  --nav-height: 72px;
  --radius: 6px;
  --radius-lg: 12px;
  --shadow: 0 2px 12px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 6px 30px rgba(0, 0, 0, 0.12);
  --transition: 0.3s ease;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-height);
}

body {
  font-family: var(--font-family);
  color: var(--color-text);
  line-height: 1.6;
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--color-accent);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--color-accent-light);
}

img {
  max-width: 100%;
  display: block;
}

ul { list-style: none; }

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

/* ===== Buttons ===== */
.btn {
  display: inline-block;
  padding: 12px 32px;
  border-radius: var(--radius);
  font-size: 15px;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition);
  border: 2px solid transparent;
  text-align: center;
}

.btn-primary {
  background: var(--color-accent);
  color: var(--color-white);
}

.btn-primary:hover {
  background: var(--color-accent-light);
  color: var(--color-white);
}

.btn-outline {
  background: transparent;
  color: var(--color-white);
  border-color: var(--color-white);
}

.btn-outline:hover {
  background: var(--color-white);
  color: var(--color-primary);
}

.btn-outline-dark {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn-outline-dark:hover {
  background: var(--color-primary);
  color: var(--color-white);
}

/* ===== Navbar ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: var(--color-white);
  border-bottom: 1px solid var(--color-border);
  z-index: 1000;
  transition: box-shadow var(--transition);
}

.navbar.scrolled {
  box-shadow: var(--shadow);
}

.navbar .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.navbar .logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 22px;
  font-weight: 700;
  color: var(--color-primary);
}

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

.nav-links {
  display: flex;
  align-items: center;
  gap: 36px;
}

.nav-links a {
  color: var(--color-text);
  font-size: 15px;
  font-weight: 500;
  position: relative;
  padding: 4px 0;
}

.nav-links a::after {
  content: "";
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--color-accent);
  transition: width var(--transition);
}

.nav-links a:hover::after,
.nav-links a.active::after {
  width: 100%;
}

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

.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  background: none;
  border: none;
  padding: 4px;
}

.hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-primary);
  transition: all var(--transition);
}

/* ===== Page Header ===== */
.page-header {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
  color: var(--color-white);
  padding: 120px 0 60px;
  text-align: center;
}

.page-header h1 {
  font-size: 40px;
  font-weight: 700;
  margin-bottom: 12px;
}

.page-header p {
  font-size: 18px;
  opacity: 0.85;
}

/* ===== Hero ===== */
.hero {
  background: linear-gradient(135deg, var(--color-primary) 0%, #0d2137 100%);
  color: var(--color-white);
  padding: 160px 0 100px;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  top: -50%;
  right: -20%;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(0, 119, 182, 0.2), transparent 70%);
  border-radius: 50%;
}

.hero .container {
  position: relative;
  z-index: 1;
}

.hero-content {
  max-width: 640px;
}

.hero h1 {
  font-size: 48px;
  font-weight: 700;
  line-height: 1.25;
  margin-bottom: 20px;
}

.hero h1 span {
  color: var(--color-accent-light);
}

.hero p {
  font-size: 18px;
  opacity: 0.85;
  margin-bottom: 36px;
  line-height: 1.7;
}

.hero-buttons {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

/* ===== Section ===== */
.section {
  padding: 80px 0;
}

.section-alt {
  background: var(--color-bg-alt);
}

.section-title {
  text-align: center;
  margin-bottom: 56px;
}

.section-title h2 {
  font-size: 32px;
  color: var(--color-primary);
  margin-bottom: 12px;
}

.section-title p {
  color: var(--color-text-light);
  font-size: 16px;
  max-width: 560px;
  margin: 0 auto;
}

/* ===== Feature Cards ===== */
.features {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.feature-card {
  background: var(--color-white);
  padding: 36px 28px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  text-align: center;
  transition: all var(--transition);
}

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

.feature-card .icon {
  width: 64px;
  height: 64px;
  margin: 0 auto 20px;
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-light));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 28px;
  color: var(--color-white);
}

.feature-card h3 {
  font-size: 18px;
  color: var(--color-primary);
  margin-bottom: 10px;
}

.feature-card p {
  color: var(--color-text-light);
  font-size: 14px;
  line-height: 1.7;
}

/* ===== Product Cards ===== */
.products-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.product-card {
  background: var(--color-white);
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  overflow: hidden;
  transition: all var(--transition);
}

.product-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
}

.product-card .card-img {
  height: 200px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
  display: flex;
  align-items: center;
  justify-content: center;
  color: rgba(255,255,255,0.3);
  font-size: 48px;
}

.product-card .card-body {
  padding: 28px;
}

.product-card h3 {
  font-size: 20px;
  color: var(--color-primary);
  margin-bottom: 10px;
}

.product-card p {
  color: var(--color-text-light);
  font-size: 14px;
  line-height: 1.7;
  margin-bottom: 16px;
}

.product-card .tags {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.product-card .tag {
  padding: 4px 12px;
  background: var(--color-bg-alt);
  color: var(--color-accent);
  border-radius: 20px;
  font-size: 12px;
}

/* ===== Partners ===== */
.partners {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 48px;
  flex-wrap: wrap;
}

.partner-item {
  width: 120px;
  height: 48px;
  background: var(--color-bg-alt);
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-muted);
  font-size: 13px;
  font-weight: 500;
}

/* ===== CTA Section ===== */
.cta {
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-light));
  color: var(--color-white);
  text-align: center;
  padding: 72px 0;
}

.cta h2 {
  font-size: 32px;
  margin-bottom: 14px;
}

.cta p {
  font-size: 16px;
  opacity: 0.9;
  margin-bottom: 28px;
}

.cta .btn {
  background: var(--color-white);
  color: var(--color-accent);
  border-color: var(--color-white);
}

.cta .btn:hover {
  background: transparent;
  color: var(--color-white);
}

/* ===== Footer ===== */
.footer {
  background: var(--color-bg-dark);
  color: rgba(255,255,255,0.7);
  padding: 56px 0 28px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 40px;
}

.footer h4 {
  color: var(--color-white);
  font-size: 16px;
  margin-bottom: 18px;
}

.footer p, .footer a {
  font-size: 14px;
  line-height: 2;
  color: rgba(255,255,255,0.6);
}

.footer a:hover {
  color: var(--color-white);
}

.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.1);
  padding-top: 24px;
  text-align: center;
  font-size: 13px;
  color: rgba(255,255,255,0.4);
}

/* ===== About Page ===== */
.about-intro {
  padding: 80px 0;
}

.about-intro .container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
}

.about-intro .about-text h2 {
  font-size: 30px;
  color: var(--color-primary);
  margin-bottom: 20px;
}

.about-intro .about-text p {
  color: var(--color-text-light);
  line-height: 1.8;
  margin-bottom: 16px;
}

.about-intro .about-img {
  height: 360px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  color: rgba(255,255,255,0.3);
  font-size: 72px;
}

/* Timeline */
.timeline {
  position: relative;
  padding-left: 40px;
  border-left: 2px solid var(--color-border);
}

.timeline-item {
  position: relative;
  margin-bottom: 36px;
  padding-left: 32px;
}

.timeline-item::before {
  content: "";
  position: absolute;
  left: -47px;
  top: 4px;
  width: 12px;
  height: 12px;
  background: var(--color-accent);
  border-radius: 50%;
  border: 3px solid var(--color-white);
  box-shadow: 0 0 0 2px var(--color-accent);
}

.timeline-item .year {
  font-size: 14px;
  color: var(--color-accent);
  font-weight: 600;
  margin-bottom: 4px;
}

.timeline-item h4 {
  font-size: 17px;
  color: var(--color-primary);
  margin-bottom: 6px;
}

.timeline-item p {
  color: var(--color-text-light);
  font-size: 14px;
}

/* Values */
.values-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.value-card {
  text-align: center;
  padding: 32px 20px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition: all var(--transition);
}

.value-card:hover {
  box-shadow: var(--shadow);
  border-color: transparent;
}

.value-card .value-icon {
  font-size: 36px;
  margin-bottom: 14px;
}

.value-card h4 {
  color: var(--color-primary);
  margin-bottom: 8px;
}

.value-card p {
  font-size: 13px;
  color: var(--color-text-light);
}

/* ===== Products Page ===== */
.product-detail {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
  padding: 60px 0;
  border-bottom: 1px solid var(--color-border);
}

.product-detail:last-child {
  border-bottom: none;
}

.product-detail .product-img {
  height: 300px;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  color: rgba(255,255,255,0.3);
  font-size: 56px;
}

.product-detail h3 {
  font-size: 26px;
  color: var(--color-primary);
  margin-bottom: 14px;
}

.product-detail p {
  color: var(--color-text-light);
  line-height: 1.8;
  margin-bottom: 16px;
}

.product-detail ul {
  list-style: none;
}

.product-detail ul li {
  padding: 6px 0 6px 24px;
  position: relative;
  color: var(--color-text-light);
  font-size: 14px;
}

.product-detail ul li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--color-accent);
  font-weight: 700;
}

.product-detail.reverse .product-img {
  order: 2;
}

.product-detail.reverse .product-info {
  order: 1;
}

/* ===== Services Page ===== */
.services-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.service-card {
  background: var(--color-white);
  padding: 40px 28px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border);
  text-align: center;
  transition: all var(--transition);
}

.service-card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-4px);
}

.service-card .service-icon {
  font-size: 42px;
  margin-bottom: 18px;
}

.service-card h3 {
  font-size: 20px;
  color: var(--color-primary);
  margin-bottom: 10px;
}

.service-card p {
  color: var(--color-text-light);
  font-size: 14px;
}

/* FAQ */
.faq-list {
  max-width: 760px;
  margin: 0 auto;
}

.faq-item {
  border-bottom: 1px solid var(--color-border);
  padding: 20px 0;
  cursor: pointer;
}

.faq-item:first-child {
  border-top: 1px solid var(--color-border);
}

.faq-question {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 17px;
  font-weight: 600;
  color: var(--color-primary);
}

.faq-question .faq-toggle {
  font-size: 20px;
  color: var(--color-accent);
  transition: transform var(--transition);
}

.faq-item.open .faq-toggle {
  transform: rotate(45deg);
}

.faq-answer {
  max-height: 0;
  overflow: hidden;
  transition: max-height var(--transition), padding var(--transition);
  color: var(--color-text-light);
  font-size: 14px;
  line-height: 1.8;
}

.faq-item.open .faq-answer {
  max-height: 200px;
  padding-top: 12px;
}

/* ===== Contact Page ===== */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
}

.contact-form {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.form-group label {
  display: block;
  font-size: 14px;
  font-weight: 500;
  color: var(--color-primary);
  margin-bottom: 6px;
}

.form-group input,
.form-group textarea,
.form-group select {
  width: 100%;
  padding: 12px 14px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  font-size: 14px;
  font-family: var(--font-family);
  color: var(--color-text);
  transition: border-color var(--transition);
  outline: none;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
  border-color: var(--color-accent);
}

.form-group textarea {
  resize: vertical;
  min-height: 120px;
}

.contact-info {
  display: flex;
  flex-direction: column;
  gap: 28px;
}

.contact-info-item {
  display: flex;
  gap: 16px;
  align-items: flex-start;
}

.contact-info-item .info-icon {
  width: 44px;
  height: 44px;
  background: var(--color-bg-alt);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  flex-shrink: 0;
}

.contact-info-item h4 {
  font-size: 15px;
  color: var(--color-primary);
  margin-bottom: 4px;
}

.contact-info-item p {
  font-size: 14px;
  color: var(--color-text-light);
}

.contact-map {
  height: 240px;
  background: var(--color-bg-alt);
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-text-muted);
  font-size: 14px;
}

/* ===== Toast Message ===== */
.toast {
  position: fixed;
  top: 100px;
  right: 20px;
  background: #2ecc71;
  color: white;
  padding: 14px 24px;
  border-radius: var(--radius);
  font-size: 14px;
  box-shadow: var(--shadow-lg);
  z-index: 2000;
  opacity: 0;
  transform: translateX(100%);
  transition: all 0.4s ease;
}

.toast.show {
  opacity: 1;
  transform: translateX(0);
}

/* ===== Papers List ===== */
.papers-list {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.paper-item {
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 16px 20px;
  border-radius: var(--radius);
  background: var(--color-white);
  border: 1px solid transparent;
  transition: all var(--transition);
  color: var(--color-text);
}

.paper-item:hover {
  border-color: var(--color-accent);
  box-shadow: var(--shadow);
  color: var(--color-text);
}

.paper-num {
  width: 40px;
  height: 40px;
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-light));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-white);
  font-size: 14px;
  font-weight: 700;
  flex-shrink: 0;
}

.paper-info {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.paper-info strong {
  font-size: 15px;
  color: var(--color-primary);
}

.paper-info em {
  font-size: 13px;
  color: var(--color-text-muted);
  font-style: normal;
}

/* ===== Responsive ===== */
@media (max-width: 1024px) {
  .features { grid-template-columns: repeat(2, 1fr); }
  .products-grid { grid-template-columns: repeat(2, 1fr); }
  .services-grid { grid-template-columns: repeat(2, 1fr); }
  .values-grid { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .about-intro .container { grid-template-columns: 1fr; }
  .contact-grid { grid-template-columns: 1fr; }
}

@media (max-width: 768px) {
  :root { --nav-height: 60px; }

  .hamburger { display: flex; }

  .nav-links {
    position: fixed;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: var(--color-white);
    flex-direction: column;
    padding: 24px;
    gap: 20px;
    border-bottom: 1px solid var(--color-border);
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: all var(--transition);
  }

  .nav-links.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: all;
  }

  .hero { padding: 120px 0 60px; }
  .hero h1 { font-size: 32px; }

  .features { grid-template-columns: 1fr; }
  .products-grid { grid-template-columns: 1fr; }
  .services-grid { grid-template-columns: 1fr; }
  .values-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }

  .product-detail { grid-template-columns: 1fr; gap: 28px; }
  .product-detail.reverse .product-img { order: -1; }

  .page-header h1 { font-size: 28px; }
  .section-title h2 { font-size: 24px; }
  .partners { gap: 24px; }
}