/* 1. 全局变量 & 字体 */
:root {
  --primary: #2b6bff;
  --primary-light: #e5efff;
  --bg: #f7f9fc;
  --card-bg: rgba(255, 255, 255, 0.75);
  --text: #2c2c2c;
  --radius: 14px;
  --shadow: 0 8px 24px rgba(44, 65, 128, 0.08);
  --transition: .3s ease;
}
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  font-family: 'Noto Sans SC', sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
}

/* 2. 顶部导航 */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 24px;
  background: rgba(255, 255, 255, 0.7);
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow);
}
.logo { height: 48px; }
nav a {
  margin-left: 24px;
  font-weight: 500;
  color: var(--primary);
  text-decoration: none;
  transition: var(--transition);
}
nav a:hover { color: #0045cc; }

/* 3. 横幅 */
.banner {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 100px 20px 120px;
  background: linear-gradient(135deg, #00c6ff 0%, #0072ff 100%);
  color: #fff;
  border-radius: 0 0 var(--radius) var(--radius);
}
.banner h1 {
  font-size: 2.8em;
  font-weight: 700;
  margin-bottom: 12px;
}
.banner p {
  font-size: 1.2em;
  margin-bottom: 30px;
  opacity: .9;
}
.btn-primary {
  padding: 12px 32px;
  background: #fff;
  color: var(--primary);
  font-weight: 600;
  border-radius: 40px;
  text-decoration: none;
  transition: var(--transition);
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.15);
}

/* 4. 主内容区 */
main {
  max-width: 1080px;
  margin: -60px auto 60px;
  padding: 0 20px;
}
section {
  margin-bottom: 70px;
}
section h2 {
  font-size: 1.8em;
  margin-bottom: 24px;
  color: var(--primary);
}

/* 5. 卡片网格 */
.product-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 28px;
}
.card {
  background: var(--card-bg);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  overflow: hidden;
  transition: var(--transition);
  backdrop-filter: blur(8px);
}
.card:hover {
  transform: translateY(-6px);
  box-shadow: 0 12px 32px rgba(44, 65, 128, 0.12);
}
.card img {
  width: 100%;
  height: 160px;
  object-fit: cover;
}
.card h3 {
  font-size: 1.1em;
  margin: 16px 16px 8px;
}
.card p {
  font-size: 0.9em;
  color: #555;
  margin: 0 16px 16px;
}

/* 6. 联系我们 */
#contact p {
  margin: 8px 0;
  font-size: 1.05em;
}
#contact i {
  color: var(--primary);
  width: 22px;
  margin-right: 8px;
}

/* 7. 页脚 */
footer {
  text-align: center;
  padding: 30px 20px;
  font-size: 0.9em;
  color: #777;
  background: #fff;
}

/* 8. 返回顶部 */
#backTop {
  position: fixed;
  right: 24px;
  bottom: 24px;
  width: 48px;
  height: 48px;
  background: var(--primary);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  transition: var(--transition);
  box-shadow: 0 4px 12px rgba(43, 107, 255, 0.35);
}
#backTop:hover { transform: scale(1.1); }

/* 9. 响应式 */
@media (max-width: 600px) {
  header { flex-direction: column; align-items: flex-start; padding: 10px 16px; }
  nav a { margin: 6px 12px 6px 0; }
  .banner h1 { font-size: 2.2em; }
  main { margin-top: -40px; }
}