/* ===== CSS 变量 & 重置 ===== */
:root {
  --primary: #185FA5;
  --primary-light: #378ADD;
  --primary-dark: #0C447C;
  --primary-bg: #E6F1FB;
  --accent: #EF9F27;
  --accent-dark: #BA7517;
  --text-primary: #0D1B2A;
  --text-secondary: #4A5568;
  --text-muted: #718096;
  --bg-white: #ffffff;
  --bg-surface: #F7FAFD;
  --bg-dark: #0a1628;
  --bg-dark-surface: #0f1f3d;
  --border: rgba(24, 95, 165, 0.15);
  --border-md: rgba(24, 95, 165, 0.25);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --shadow-sm: 0 2px 8px rgba(24, 95, 165, 0.08);
  --shadow-md: 0 4px 20px rgba(24, 95, 165, 0.12);
  --shadow-lg: 0 8px 40px rgba(24, 95, 165, 0.18);
  --transition: 0.25s cubic-bezier(0.4,0,0.2,1);
  --font: 'PingFang SC', 'Microsoft YaHei', 'Helvetica Neue', sans-serif;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font);
  color: var(--text-primary);
  background: var(--bg-white);
  line-height: 1.6;
  overflow-x: hidden;
}
a { text-decoration: none; color: inherit; }
img { max-width: 100%; display: block; }
ul { list-style: none; }

/* ===== 通用 ===== */
.container { max-width: 1100px; margin: 0 auto; padding: 0 24px; }
.section { padding: 80px 0; }
.bg-dark-section { background: var(--bg-surface); }

.section-header {
  text-align: center;
  margin-bottom: 48px;
}
.section-tag {
  display: inline-block;
  background: var(--primary-bg);
  color: var(--primary);
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 1.5px;
  text-transform: uppercase;
  padding: 4px 12px;
  border-radius: 20px;
  margin-bottom: 12px;
}
.section-title {
  font-size: clamp(22px, 3vw, 30px);
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.3;
}
.section-more {
  display: inline-block;
  margin-top: 10px;
  color: var(--primary);
  font-size: 14px;
  font-weight: 500;
  transition: var(--transition);
}
.section-more:hover { color: var(--primary-dark); }

/* ===== 按钮 ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  border-radius: var(--radius-md);
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  border: 2px solid transparent;
}
.btn-primary {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}
.btn-primary:hover { background: var(--primary-dark); border-color: var(--primary-dark); transform: translateY(-2px); box-shadow: var(--shadow-md); }
.btn-outline {
  background: transparent;
  color: #fff;
  border-color: rgba(255,255,255,0.5);
}
.btn-outline:hover { background: rgba(255,255,255,0.1); border-color: #fff; transform: translateY(-2px); }
.btn-outline-sm {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 22px;
  border-radius: var(--radius-md);
  font-size: 14px;
  font-weight: 600;
  color: var(--primary);
  border: 1.5px solid var(--primary);
  transition: var(--transition);
}
.btn-outline-sm:hover { background: var(--primary); color: #fff; transform: translateY(-2px); }
.btn-sm {
  padding: 8px 20px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  font-weight: 600;
  background: var(--primary);
  color: #fff;
  display: inline-block;
  transition: var(--transition);
}
.btn-sm:hover { background: var(--primary-dark); transform: translateY(-1px); }

/* ===== 导航栏 ===== */
.navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  background: transparent;
  transition: background var(--transition), box-shadow var(--transition);
  padding: 0;
}
.navbar.scrolled {
  background: rgba(10, 22, 40, 0.95);
  backdrop-filter: blur(12px);
  box-shadow: 0 2px 20px rgba(0,0,0,0.3);
}
.nav-container {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 24px;
  height: 68px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.nav-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  color: #fff;
  font-size: 18px;
  font-weight: 700;
}
.logo-atom {
  font-size: 24px;
  color: var(--accent);
  animation: spin 8s linear infinite;
  display: inline-block;
}
@keyframes spin { from{transform:rotate(0deg)} to{transform:rotate(360deg)} }
.visitor-count {
  display: flex !important;
  align-items: center;
  gap: 4px;
  color: rgba(255,255,255,0.85);
  font-size: 12px;
  font-weight: 500;
  padding: 4px 10px;
  border-radius: 20px;
  background: rgba(255,255,255,0.12);
  border: 1px solid rgba(255,255,255,0.25);
  white-space: nowrap;
  transition: var(--transition);
  flex-shrink: 0;
  margin-left: 12px;
}
.visitor-count svg { opacity: 0.8; }
.navbar.scrolled .visitor-count {
  color: rgba(255,255,255,0.75);
  background: rgba(255,255,255,0.1);
}
.visitor-count { animation: fadeInCount 0.3s ease 0.5s both; }
@keyframes fadeInCount { from { opacity: 0; transform: translateX(10px); } to { opacity: 1; transform: translateX(0); } }
.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
}
.nav-link {
  color: rgba(255,255,255,0.8);
  font-size: 14px;
  padding: 8px 14px;
  border-radius: var(--radius-sm);
  transition: var(--transition);
}
.nav-link:hover, .nav-link.active { color: #fff; background: rgba(255,255,255,0.1); }
.nav-btn {
  background: var(--primary);
  color: #fff !important;
  border-radius: var(--radius-md);
  padding: 8px 18px;
  margin-left: 8px;
}
.nav-btn:hover { background: var(--primary-light) !important; }
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}
.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: #fff;
  border-radius: 2px;
  transition: var(--transition);
}

/* ===== 英雄区 ===== */
.hero {
  position: relative;
  min-height: 100vh;
  background: linear-gradient(135deg, #041a3a 0%, #0a2d5e 40%, #0d3b7a 70%, #0f4494 100%);
  display: flex;
  align-items: center;
  overflow: hidden;
  padding-top: 68px;
}
.hero-bg {
  position: absolute;
  inset: 0;
  overflow: hidden;
}
#particleCanvas {
  position: absolute;
  inset: 0;
  opacity: 0.4;
}
.hero-content {
  position: relative;
  z-index: 2;
  max-width: 1100px;
  margin: 0 auto;
  padding: 60px 24px;
  flex: 1;
}
.hero-badge {
  display: inline-block;
  background: rgba(55, 138, 221, 0.2);
  border: 1px solid rgba(55, 138, 221, 0.4);
  color: #85B7EB;
  font-size: 13px;
  font-weight: 500;
  padding: 6px 16px;
  border-radius: 20px;
  margin-bottom: 20px;
}
.hero-title {
  font-size: clamp(36px, 5vw, 64px);
  font-weight: 800;
  color: #fff;
  line-height: 1.15;
  margin-bottom: 20px;
  letter-spacing: -1px;
}
.highlight {
  color: var(--accent);
  position: relative;
}
.hero-sub {
  font-size: clamp(15px, 2vw, 18px);
  color: rgba(255,255,255,0.75);
  max-width: 520px;
  line-height: 1.7;
  margin-bottom: 36px;
}
.hero-actions {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  margin-bottom: 48px;
}
.hero-stats {
  display: flex;
  align-items: center;
  gap: 24px;
}
.stat { display: flex; flex-direction: column; }
.stat-num { font-size: 28px; font-weight: 800; color: #fff; line-height: 1; }
.stat-label { font-size: 12px; color: rgba(255,255,255,0.6); margin-top: 4px; }
.stat-divider { width: 1px; height: 40px; background: rgba(255,255,255,0.2); }

/* 原子轨道动画 */
.hero-visual {
  position: absolute;
  right: 5%;
  top: 50%;
  transform: translateY(-50%);
  z-index: 1;
  opacity: 0.6;
}
.orbit-system {
  position: relative;
  width: 300px;
  height: 300px;
}
.nucleus {
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  width: 24px; height: 24px;
  background: var(--accent);
  border-radius: 50%;
  box-shadow: 0 0 20px var(--accent), 0 0 40px rgba(239,159,39,0.4);
}
.orbit {
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  border: 1px solid rgba(55,138,221,0.4);
  border-radius: 50%;
}
.orbit-1 { width: 100px; height: 100px; animation: rotateCW 4s linear infinite; }
.orbit-2 { width: 180px; height: 180px; transform: translate(-50%, -50%) rotateX(60deg); animation: rotateCCW 7s linear infinite; }
.orbit-3 { width: 260px; height: 260px; transform: translate(-50%, -50%) rotateX(30deg) rotateY(45deg); animation: rotateCW 11s linear infinite; }
.electron {
  position: absolute;
  width: 10px; height: 10px;
  background: #85B7EB;
  border-radius: 50%;
  box-shadow: 0 0 8px #85B7EB;
}
.e1 { top: -5px; left: calc(50% - 5px); }
.e2 { top: -5px; left: calc(50% - 5px); }
.e3 { top: -5px; left: calc(50% - 5px); }
@keyframes rotateCW { from{transform: translate(-50%,-50%) rotate(0deg)} to{transform: translate(-50%,-50%) rotate(360deg)} }
@keyframes rotateCCW { from{transform: translate(-50%,-50%) rotateX(60deg) rotate(0deg)} to{transform: translate(-50%,-50%) rotateX(60deg) rotate(-360deg)} }

/* ===== 模块卡片 ===== */
.modules-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
}
.module-card {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px 24px;
  position: relative;
  transition: var(--transition);
  overflow: hidden;
  display: block;
}
.module-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  transition: var(--transition);
}
.module-mechanics::before { background: linear-gradient(90deg, #185FA5, #378ADD); }
.module-electricity::before { background: linear-gradient(90deg, #EF9F27, #FAC775); }
.module-optics::before { background: linear-gradient(90deg, #1D9E75, #5DCAA5); }
.module-modern::before { background: linear-gradient(90deg, #534AB7, #7F77DD); }
.module-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-lg);
  border-color: var(--border-md);
}
.module-icon {
  width: 52px; height: 52px;
  margin-bottom: 16px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
}
/* 四大板块配色 */
.module-resources::before { background: linear-gradient(90deg, #185FA5, #378ADD); }
.module-sim::before { background: linear-gradient(90deg, #0F6E56, #1D9E75); }
.module-esp32::before { background: linear-gradient(90deg, #EF9F27, #FAC775); }
.module-ai::before { background: linear-gradient(90deg, #7B3AED, #A78BFA); }

.module-resources .module-icon { background: #E6F1FB; color: #185FA5; }
.module-sim .module-icon { background: #E1F5EE; color: #0F6E56; }
.module-esp32 .module-icon { background: #FAF3E0; color: #BA7517; }
.module-ai .module-icon { background: #F0EAFF; color: #7B3AED; }

.module-tags { display: flex; gap: 6px; margin-bottom: 16px; flex-wrap: wrap; }
.module-tag { background: var(--primary-bg); color: var(--primary); font-size: 11px; padding: 2px 8px; border-radius: 8px; font-weight: 500; }
.module-sim .module-tag { background: #E1F5EE; color: #0F6E56; }
.module-esp32 .module-tag { background: #FAF3E0; color: #BA7517; }
.module-ai .module-tag { background: #F0EAFF; color: #7B3AED; }
.module-icon svg { width: 32px; height: 32px; }
.module-card h3 { font-size: 18px; font-weight: 700; margin-bottom: 8px; color: var(--text-primary); }
.module-card p { font-size: 13px; color: var(--text-muted); line-height: 1.6; margin-bottom: 16px; }
.module-arrow {
  font-size: 18px;
  color: var(--primary);
  position: absolute;
  bottom: 20px;
  right: 24px;
  transition: var(--transition);
}
.module-card:hover .module-arrow { transform: translateX(4px); }

/* ===== 资源卡片 ===== */
.resources-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 20px;
}
.resource-card {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: var(--transition);
}
.resource-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); }
.resource-type {
  padding: 6px 14px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 1.5px;
  text-transform: uppercase;
}
.type-pdf { background: #FCEBEB; color: #A32D2D; }
.type-video { background: #E1F5EE; color: #0F6E56; }
.type-ppt { background: #FAEEDA; color: #854F0B; }
.resource-body { padding: 16px; flex: 1; }
.resource-body h4 { font-size: 15px; font-weight: 600; margin-bottom: 8px; color: var(--text-primary); }
.resource-body p { font-size: 13px; color: var(--text-muted); line-height: 1.5; margin-bottom: 12px; }
.resource-meta { display: flex; align-items: center; gap: 8px; }
.tag {
  background: var(--primary-bg);
  color: var(--primary);
  font-size: 11px;
  padding: 2px 8px;
  border-radius: 10px;
  font-weight: 500;
}
.resource-date { font-size: 12px; color: var(--text-muted); margin-left: auto; }
.resource-download {
  display: block;
  text-align: center;
  padding: 10px;
  background: var(--bg-surface);
  color: var(--primary);
  font-size: 13px;
  font-weight: 600;
  border-top: 1px solid var(--border);
  transition: var(--transition);
}
.resource-download:hover { background: var(--primary); color: #fff; }

/* ===== 公式速查 ===== */
.formula-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 24px;
  flex-wrap: wrap;
}
.ftab {
  padding: 8px 20px;
  border-radius: 20px;
  border: 1px solid var(--border);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  background: var(--bg-white);
  color: var(--text-secondary);
  transition: var(--transition);
}
.ftab.active, .ftab:hover { background: var(--primary); color: #fff; border-color: var(--primary); }
.formula-group { display: none; }
.formula-group.active { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 12px; }
.formula-item {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 14px 16px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  transition: var(--transition);
}
.formula-item:hover { border-color: var(--primary); box-shadow: var(--shadow-sm); }
.formula-name { font-size: 13px; color: var(--text-muted); font-weight: 500; }
.formula-expr {
  font-size: 18px;
  font-weight: 700;
  color: var(--primary-dark);
  font-family: 'Georgia', serif;
  letter-spacing: 0.5px;
}
.formula-note { font-size: 12px; color: var(--text-muted); }

/* ===== 实验预览 ===== */
.exp-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 20px;
}
.exp-card {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: var(--transition);
}
.exp-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); }
.exp-thumb {
  height: 160px;
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
}
.exp-thumb-1 { background: linear-gradient(135deg, #0C447C, #185FA5); }
.exp-thumb-2 { background: linear-gradient(135deg, #3B6D11, #639922); }
.exp-thumb-3 { background: linear-gradient(135deg, #3C3489, #534AB7); }
.exp-play {
  width: 56px; height: 56px;
  background: rgba(255,255,255,0.2);
  border: 2px solid rgba(255,255,255,0.6);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  color: #fff;
  cursor: pointer;
  transition: var(--transition);
}
.exp-card:hover .exp-play { background: rgba(255,255,255,0.35); transform: scale(1.1); }
.exp-badge {
  position: absolute;
  top: 12px; left: 12px;
  background: rgba(255,255,255,0.2);
  color: #fff;
  font-size: 11px;
  font-weight: 600;
  padding: 3px 10px;
  border-radius: 12px;
}
.exp-info { padding: 16px; }
.exp-info h4 { font-size: 15px; font-weight: 600; margin-bottom: 6px; color: var(--text-primary); }
.exp-info p { font-size: 13px; color: var(--text-muted); line-height: 1.5; margin-bottom: 10px; }
.exp-meta { display: flex; gap: 12px; font-size: 12px; color: var(--text-muted); }

/* ===== 关于预览 ===== */
.about-container {
  display: flex;
  align-items: center;
  gap: 80px;
}
.about-visual {
  flex-shrink: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
}
.avatar-ring {
  width: 180px; height: 180px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--primary), var(--primary-light));
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 0 0 8px var(--primary-bg), 0 0 0 16px rgba(24,95,165,0.1);
}
.avatar-inner {
  width: 160px; height: 160px;
  border-radius: 50%;
  background: linear-gradient(135deg, #042C53, #0C447C);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 64px;
  font-weight: 800;
  color: rgba(255,255,255,0.9);
}
.about-badges { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; }
.badge-chip {
  background: var(--primary-bg);
  color: var(--primary);
  font-size: 12px;
  font-weight: 500;
  padding: 4px 12px;
  border-radius: 12px;
  border: 1px solid rgba(24,95,165,0.2);
}
.about-text h2 { font-size: 28px; font-weight: 700; margin-bottom: 16px; color: var(--text-primary); }
.about-text p { font-size: 15px; color: var(--text-secondary); line-height: 1.8; margin-bottom: 14px; }

/* ===== 页脚 ===== */
.footer {
  background: var(--bg-dark);
  color: rgba(255,255,255,0.7);
  padding: 60px 0 0;
}
.footer-inner {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 2fr;
  gap: 40px;
  padding-bottom: 40px;
  border-bottom: 1px solid rgba(255,255,255,0.1);
}
.footer-brand {
  display: flex;
  flex-direction: column;
  gap: 8px;
  font-size: 18px;
  font-weight: 700;
  color: #fff;
}
.footer-brand .logo-atom { font-size: 28px; }
.footer-brand p { font-size: 13px; color: rgba(255,255,255,0.4); font-weight: 400; }
.footer-links { display: flex; flex-direction: column; gap: 8px; }
.footer-links h5 { color: #fff; font-size: 14px; font-weight: 600; margin-bottom: 4px; }
.footer-links a { font-size: 13px; transition: var(--transition); }
.footer-links a:hover { color: #fff; }
.footer-contact h5 { color: #fff; font-size: 14px; font-weight: 600; margin-bottom: 8px; }
.footer-contact p { font-size: 13px; line-height: 1.6; margin-bottom: 12px; }
.footer-bottom {
  text-align: center;
  padding: 20px;
  font-size: 12px;
  color: rgba(255,255,255,0.3);
}

/* ===== 响应式 ===== */
@media (max-width: 900px) {
  .hero-visual { display: none; }
  .about-container { flex-direction: column; gap: 40px; }
  .footer-inner { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 680px) {
  .nav-links { 
    display: none;
    position: fixed;
    top: 68px; left: 0; right: 0;
    background: rgba(10,22,40,0.98);
    flex-direction: column;
    padding: 20px;
    gap: 4px;
  }
  .nav-links.open { display: flex; }
  .nav-toggle { display: flex; }
  .footer-inner { grid-template-columns: 1fr; }
  .section { padding: 56px 0; }
  .hero-stats { flex-wrap: wrap; gap: 16px; }
}

/* ===== 页面通用头部（内页） ===== */
.page-hero {
  background: linear-gradient(135deg, #041a3a 0%, #0a2d5e 50%, #0f4494 100%);
  padding: 120px 0 60px;
  color: #fff;
  text-align: center;
}
.page-hero h1 { font-size: clamp(28px, 4vw, 42px); font-weight: 800; margin-bottom: 12px; }
.page-hero p { font-size: 16px; color: rgba(255,255,255,0.7); }

/* ===== 资源页 ===== */
.filter-bar {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 32px;
}
.filter-btn {
  padding: 7px 16px;
  border-radius: 20px;
  border: 1px solid var(--border);
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  background: var(--bg-white);
  color: var(--text-secondary);
  transition: var(--transition);
}
.filter-btn.active, .filter-btn:hover { background: var(--primary); color: #fff; border-color: var(--primary); }

/* ===== 联系页 ===== */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1.4fr;
  gap: 40px;
  align-items: start;
}
.contact-info { display: flex; flex-direction: column; gap: 20px; }
.contact-item {
  display: flex;
  gap: 16px;
  align-items: flex-start;
  padding: 20px;
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
}
.contact-icon {
  width: 44px; height: 44px;
  background: var(--primary-bg);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  flex-shrink: 0;
}
.contact-item h4 { font-size: 14px; font-weight: 600; margin-bottom: 4px; }
.contact-item p { font-size: 13px; color: var(--text-muted); }
.contact-form {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
}
.contact-form h3 { font-size: 18px; font-weight: 700; margin-bottom: 24px; }
.form-group { margin-bottom: 16px; }
.form-group label { display: block; font-size: 13px; font-weight: 500; margin-bottom: 6px; color: var(--text-secondary); }
.form-group input, .form-group textarea, .form-group select {
  width: 100%;
  padding: 10px 14px;
  border: 1px solid var(--border-md);
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-family: var(--font);
  color: var(--text-primary);
  background: var(--bg-white);
  transition: var(--transition);
  outline: none;
}
.form-group input:focus, .form-group textarea:focus, .form-group select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(24,95,165,0.1);
}
.form-group textarea { height: 120px; resize: vertical; }
.form-submit {
  width: 100%;
  padding: 12px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: var(--radius-md);
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  font-family: var(--font);
}
.form-submit:hover { background: var(--primary-dark); transform: translateY(-2px); box-shadow: var(--shadow-md); }

/* ===== 知识讲堂卡片 ===== */
.knowledge-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 24px;
}
.knowledge-card {
  background: var(--bg-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  transition: var(--transition);
}
.knowledge-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-md); }
.knowledge-card .card-num {
  font-size: 40px;
  font-weight: 800;
  color: var(--primary-bg);
  line-height: 1;
  margin-bottom: 12px;
}
.knowledge-card h3 { font-size: 17px; font-weight: 700; margin-bottom: 8px; color: var(--text-primary); }
.knowledge-card p { font-size: 13px; color: var(--text-muted); line-height: 1.7; }

/* ===== 滚动动画 ===== */
.fade-up {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.fade-up.visible { opacity: 1; transform: translateY(0); }