/* ==========================================
   1. CSS VARIABLES & RESET (全局变量与重置)
   ================================---------- */
:root {
  --color-chem: #0056B3;
  --color-vanguard: #333333;
  --color-success: #00875A;
  --color-bg: #FFFFFF;
  --color-surface: #F8FAFC;
  --color-text: #475569;
  --color-heading: #0F172A;
  --border-color: #E2E8F0;
  --font-main: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --transition-smooth: all 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

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

body {
  font-family: var(--font-main);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.7;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

a {
  text-decoration: none;
  color: inherit;
}

ul {
  list-style: none;
}

/* ==========================================
   2. GLOBAL COMPONENTS (通栏导航与页脚)
   ================================---------- */
header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  transition: var(--transition-smooth);
}

header.scrolled {
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.05);
}

.nav-container {
  width: 100%;
  padding: 20px 80px; 
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo-container {
  display: flex;
  flex-direction: column;
}

.logo-text {
  font-size: 26px;
  font-weight: 800;
  letter-spacing: -0.5px;
}

.logo-chem {
  color: var(--color-chem);
}

.logo-vanguard {
  color: var(--color-vanguard);
}

.logo-sub {
  font-size: 10px;
  color: var(--color-text);
  letter-spacing: 0.5px;
  text-transform: uppercase;
  margin-top: -3px;
}

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

.nav-links a {
  font-size: 15px;
  font-weight: 500;
  color: var(--color-text);
  transition: var(--transition-smooth);
}

.nav-links a:hover, .nav-links a.active {
  color: var(--color-chem);
}

/* 旗舰通栏页脚优化样式 */
footer {
  background-color: #0B0F19;
  color: #94A3B8;
  padding: 80px 40px 30px;
  margin-top: 140px;
  width: 100%;
  border-top: 1px solid rgba(255, 255, 255, 0.05);
}

.footer-container {
  width: 100%;
  display: grid;
  grid-template-columns: 2fr 1.2fr 1.5fr 1.2fr;
  gap: 40px;
  padding-bottom: 50px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}

.footer-col h4 {
  color: #FFFFFF;
  font-size: 15px;
  font-weight: 600;
  margin-bottom: 20px;
  letter-spacing: 0.5px;
}

.footer-col ul {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-col a {
  font-size: 14px;
  color: #94A3B8;
  transition: var(--transition-smooth);
}

.footer-col a:hover {
  color: #FFFFFF;
  padding-left: 4px;
}

.footer-bottom {
  width: 100%;
  margin-top: 30px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 13px;
  color: #64748B;
}

/* ==========================================
   3. HERO SECTIONS & LAYOUT (真正全屏铺开)
   ================================---------- */

.hero {
  width: 100%;
  height: 90vh;
  min-height: 700px;
  display: flex;
  align-items: center;
  position: relative;
  background-size: cover;
  background-position: center;
  margin-top: 76px;
}

.hero-overlay {
  position: absolute;
  top: 0; left: 0; width: 100%; height: 100%;
  background: linear-gradient(90deg, rgba(15, 23, 42, 0.92) 0%, rgba(15, 23, 42, 0.5) 100%);
}

.hero-content {
  position: relative;
  width: 100%;
  padding: 0 100px; 
  color: #FFFFFF;
}

.hero-content h1 {
  font-size: 58px;
  font-weight: 800;
  line-height: 1.15;
  margin-bottom: 24px;
  max-width: 900px;
}

.hero-content p {
  font-size: 20px;
  color: #CBD5E1;
  max-width: 750px;
  margin-bottom: 40px;
  font-weight: 300;
}

.btn-primary {
  display: inline-block;
  background-color: var(--color-chem);
  color: #FFFFFF;
  padding: 16px 36px;
  border-radius: 6px;
  font-weight: 600;
  font-size: 16px;
  transition: var(--transition-smooth);
  box-shadow: 0 4px 20px rgba(0, 86, 179, 0.3);
}

.btn-primary:hover {
  transform: translateY(-3px);
  box-shadow: 0 8px 30px rgba(0, 86, 179, 0.4);
}

section {
  width: 100%;
  padding: 140px 80px;
}

.section-header {
  text-align: center;
  max-width: 850px;
  margin: 0 auto 90px;
}

.section-header span {
  color: var(--color-chem);
  font-weight: 600;
  text-transform: uppercase;
  font-size: 13px;
  letter-spacing: 2px;
  display: block;
  margin-bottom: 12px;
}

.section-header h2 {
  font-size: 42px;
  font-weight: 700;
  color: var(--color-heading);
  line-height: 1.3;
}

.grid-3 {
  width: 100%;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 40px;
  max-width: 1600px;
  margin: 0 auto;
}

.card {
  background: #FFFFFF;
  padding: 50px 40px;
  border-radius: 12px;
  border: 1px solid var(--border-color);
  transition: var(--transition-smooth);
  position: relative;
}

.card:hover {
  transform: translateY(-8px);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.06);
  border-color: rgba(0, 86, 179, 0.2);
}

.card h3 {
  font-size: 22px;
  color: var(--color-heading);
  margin-bottom: 16px;
  font-weight: 600;
}

.card p {
  font-size: 15px;
  color: var(--color-text);
  line-height: 1.8;
}

.form-container {
  width: 100%;
  max-width: 900px;
  margin: 0 auto;
  background: #FFFFFF;
  padding: 60px;
  border-radius: 16px;
  border: 1px solid var(--border-color);
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.04);
}

.form-group {
  margin-bottom: 28px;
}

.form-group label {
  display: block;
  font-weight: 600;
  color: var(--color-heading);
  margin-bottom: 10px;
  font-size: 14px;
}

.form-group input, .form-group textarea, .form-group select {
  width: 100%;
  padding: 16px;
  border: 1px solid var(--border-color);
  border-radius: 8px;
  font-family: var(--font-main);
  font-size: 15px;
  transition: var(--transition-smooth);
  background: var(--color-surface);
}

.form-group input:focus, .form-group textarea:focus, .form-group select:focus {
  outline: none;
  border-color: var(--color-chem);
  background: #FFFFFF;
  box-shadow: 0 0 0 4px rgba(0, 86, 179, 0.1);
}

.reveal {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.8s cubic-bezier(0.16, 1, 0.3, 1), transform 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}
.reveal.active {
  opacity: 1;
  transform: translateY(0);
}

.hero-minimal {
  width: 100%;
  min-height: 85vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  background: radial-gradient(circle at 50% 30%, #F8FAFC 0%, #FFFFFF 70%);
  padding: 140px 80px 80px;
  margin-top: 76px;
  position: relative;
  overflow: hidden;
}

.hero-minimal-content {
  max-width: 1100px;
  margin: 0 auto;
}

.hero-brand-title {
  font-size: 72px;
  font-weight: 900;
  letter-spacing: -1.5px;
  margin-bottom: 20px;
  line-height: 1.1;
}

.hero-minimal h1 {
  font-size: 42px;
  font-weight: 700;
  color: var(--color-heading);
  margin-bottom: 24px;
  line-height: 1.25;
}

.hero-minimal p {
  font-size: 18px;
  color: var(--color-text);
  max-width: 800px;
  margin: 0 auto 40px;
  font-weight: 400;
}

.hero-cta-group {
  display: flex;
  gap: 20px;
  justify-content: center;
  align-items: center;
}

.btn-secondary {
  display: inline-block;
  background-color: #FFFFFF;
  color: var(--color-heading);
  border: 1px solid var(--border-color);
  padding: 16px 36px;
  border-radius: 6px;
  font-weight: 600;
  font-size: 16px;
  transition: var(--transition-smooth);
}

.btn-secondary:hover {
  border-color: var(--color-chem);
  color: var(--color-chem);
  transform: translateY(-3px);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.04);
}



/* ==========================================
   4. RESPONSIVE MEDIA QUERIES & MOBILE MENU
   ================================---------- */

/* 移动端汉堡菜单按钮默认在PC端隐藏 */
.menu-toggle {
  display: none;
  flex-direction: column;
  justify-content: space-between;
  width: 28px;
  height: 20px;
  background: transparent;
  border: none;
  cursor: pointer;
  z-index: 1001;
}

.menu-toggle span {
  display: block;
  width: 100%;
  height: 2px;
  background-color: var(--color-heading);
  transition: var(--transition-smooth);
  border-radius: 2px;
}

/* 平板与大屏设备适配 (最大宽度 1024px) */
@media (max-width: 1024px) {
  .nav-container {
    padding: 20px 40px;
  }
  
  section {
    padding: 100px 40px;
  }
  
  .hero-content {
    padding: 0 50px;
  }
  
  .hero-content h1 {
    font-size: 46px;
  }

  .grid-3 {
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
  }

  .footer-container {
    grid-template-columns: repeat(2, 1fr);
    gap: 30px;
  }

  .form-container {
    padding: 40px;
  }
  
  .hero-brand-title {
    font-size: 56px;
  }
}

/* 移动端设备适配 (最大宽度 768px) */
@media (max-width: 768px) {
  .nav-container {
    padding: 16px 20px;
  }

  /* 显示汉堡菜单按钮 */
  .menu-toggle {
    display: flex;
  }

  /* 移动端抽屉式导航栏 */
  .nav-links {
    position: fixed;
    top: 0;
    right: -100%;
    width: 75%;
    height: 100vh;
    background: #FFFFFF;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    gap: 24px;
    box-shadow: -10px 0 30px rgba(0, 0, 0, 0.1);
    transition: right 0.4s cubic-bezier(0.16, 1, 0.3, 1);
    z-index: 1000;
  }

  /* 激活状态：展开导航 */
  .nav-links.active {
    right: 0;
  }

  /* 汉堡按钮点击后的动态叉号动画 */
  .menu-toggle.active span:nth-child(1) {
    transform: translateY(9px) rotate(45deg);
  }
  .menu-toggle.active span:nth-child(2) {
    opacity: 0;
  }
  .menu-toggle.active span:nth-child(3) {
    transform: translateY(-9px) rotate(-45deg);
  }

  .nav-links a {
    font-size: 18px;
  }

  .hero {
    height: 80vh;
    min-height: 550px;
    margin-top: 65px;
  }

  .hero-content {
    padding: 0 24px;
  }

  .hero-content h1, 
  .hero-minimal h1 {
    font-size: 36px;
  }

  .hero-content p, 
  .hero-minimal p {
    font-size: 16px;
  }

  .grid-3 {
    grid-template-columns: 1fr;
    gap: 20px;
  }

  section {
    padding: 70px 20px;
  }

  .section-header {
    margin-bottom: 50px;
  }

  .section-header h2 {
    font-size: 30px;
  }

  .card {
    padding: 30px 24px;
  }

  .form-container {
    padding: 24px;
  }

  .hero-minimal {
    padding: 100px 20px 60px;
    margin-top: 65px;
  }

  .hero-brand-title {
    font-size: 40px;
  }

  .hero-cta-group {
    flex-direction: column;
    width: 100%;
  }

  .hero-cta-group a {
    width: 100%;
    text-align: center;
  }

  .footer-container {
    grid-template-columns: 1fr;
    gap: 30px;
  }

  footer {
    padding: 50px 20px 20px;
    margin-top: 80px;
  }

  .footer-bottom {
    flex-direction: column;
    gap: 12px;
    text-align: center;
  }
}