/* 全局样式增强 */
body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

main {
  flex: 1;
}

/* 卡片悬停效果 */
article {
  transition: transform 0.2s, box-shadow 0.2s;
}

article:hover {
  transform: translateY(-4px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.15) !important;
}

/* 导航激活状态 */
.nav a.active {
  background: rgba(255,255,255,0.3);
  font-weight: bold;
}

/* 响应式布局优化 */
@media (max-width: 768px) {
  .container {
    padding: 0 0.75rem;
  }

  h1 {
    font-size: 1.5rem !important;
  }

  h2 {
    font-size: 1.3rem !important;
  }

  article, section {
    padding: 1rem !important;
  }
}

/* 返回顶部按钮 */
.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  background: #2c5aa0;
  color: white;
  width: 50px;
  height: 50px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.3s;
  box-shadow: 0 2px 8px rgba(0,0,0,0.2);
}

.back-to-top.show {
  opacity: 1;
}

.back-to-top:hover {
  background: #1a3a6d;
}

/* 平滑滚动 */
html {
  scroll-behavior: smooth;
}