/* ========== 基础样式 ========== */
body {
  margin: 0;
  font-family: "Helvetica Neue", "PingFang SC", sans-serif;
  background-color: #f9fafb;
  color: #333;
  line-height: 1.7;
  scroll-behavior: smooth;
}

/* ========== 导航栏 ========== */
.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: #003d3b;
  color: #fff;
  padding: 1rem 2rem;
  position: sticky;
  top: 0;
  z-index: 20;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}
.logo {
  font-weight: 600;
  font-size: 1.2rem;
  letter-spacing: 1px;
}
.nav-links {
  display: flex;
  gap: 1.5rem;
}
.nav-links a {
  color: #fff;
  text-decoration: none;
  font-weight: 400;
  transition: opacity 0.3s;
}
.nav-links a:hover {
  opacity: 0.7;
}
.menu-btn {
  display: none;
  font-size: 1.5rem;
  background: none;
  color: white;
  border: none;
  cursor: pointer;
}

/* ========== 横幅区 ========== */
.hero {
  background: linear-gradient(to bottom right, #00695c, #004d40);
  color: white;
  text-align: center;
  padding: 6rem 1rem;
}
.hero h1 {
  font-size: 2.6rem;
  margin-bottom: 0.5rem;
}
.hero p {
  font-size: 1.3rem;
  margin-bottom: 2rem;
}
.btn {
  display: inline-block;
  background-color: #ffc107;
  color: #000;
  padding: 0.8rem 1.5rem;
  border-radius: 4px;
  text-decoration: none;
  font-weight: bold;
  transition: background 0.3s;
}
.btn:hover {
  background-color: #ffb300;
}

/* ========== 内容区 ========== */
.content {
  max-width: 900px;
  margin: 3rem auto;
  padding: 0 1.5rem;
}
.content h2 {
  color: #004d40;
  border-left: 4px solid #004d40;
  padding-left: 0.6rem;
}
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.5rem;
  margin-top: 1.5rem;
}
.card {
  background-color: #e0f2f1;
  padding: 1.5rem;
  border-radius: 10px;
  transition: transform 0.3s, box-shadow 0.3s;
}
.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

/* ========== 页脚 ========== */
.footer {
  text-align: center;
  padding: 2rem 1rem;
  background-color: #003d3b;
  color: white;
  font-size: 0.9rem;
}

/* ========== 动画效果 ========== */
.fade-in {
  opacity: 0;
  transform: translateY(40px);
  transition: opacity 1s ease-out, transform 1s ease-out;
}
.fade-in.appear {
  opacity: 1;
  transform: translateY(0);
}
.delay {
  transition-delay: 0.3s;
}
.delay-2 {
  transition-delay: 0.6s;
}

/* ========== 响应式设计 ========== */
@media (max-width: 768px) {
  .nav-links {
    display: none;
    flex-direction: column;
    background: #004d40;
    position: absolute;
    top: 70px;
    right: 0;
    width: 60%;
    padding: 1rem;
  }
  .nav-links.active {
    display: flex;
  }
  .menu-btn {
    display: block;
  }
  .hero h1 {
    font-size: 2rem;
  }
  .hero p {
    font-size: 1.1rem;
  }
}