/* 
整体样式定义
主色调采用深蓝色系，辅色为银灰色，点缀色为亮橙色
使用CSS变量便于统一管理色彩
容器使用响应式布局，适配不同屏幕尺寸
添加平滑过渡和关键帧动画提升用户体验
*/

/* 定义颜色变量 */
:root {
  --primary-color: #0D47A1; /* 主色调：深蓝 */
  --secondary-color: #B0BEC5; /* 辅色：银灰 */
  --accent-color: #FF6F00; /* 点缀色：亮橙 */
  --background-color: #F5F5F5; /* 背景色：浅灰 */
  --text-color: #333333; /* 正文字体颜色 */
  --header-height: 60px; /* 顶部导航高度 */
}

/* 全局样式 */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Roboto', sans-serif;
  background: linear-gradient(135deg, var(--background-color), var(--secondary-color));
  color: var(--text-color);
  line-height: 1.6;
  overflow-x: hidden;
}

/* 顶部导航栏样式 */
.top-nav {
  position: fixed;
  top: 0;
  width: 100%;
  height: var(--header-height);
  background-color: var(--primary-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 30px;
  z-index: 1000;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.top-nav .logo {
  font-size: 1.5rem;
  color: #FFFFFF;
  text-decoration: none;
}

.top-nav .menu {
  display: flex;
  gap: 20px;
}

.top-nav .menu a {
  color: #FFFFFF;
  text-decoration: none;
  font-size: 1rem;
  transition: color 0.3s ease;
}

.top-nav .menu a:hover {
  color: var(--accent-color);
}

/* 侧边导航栏样式 */
.side-nav {
  position: fixed;
  top: var(--header-height);
  left: 0;
  width: 200px;
  height: calc(100% - var(--header-height));
  background-color: var(--secondary-color);
  padding: 20px;
  box-shadow: 2px 0 5px rgba(0, 0, 0, 0.1);
  overflow-y: auto;
}

.side-nav a {
  display: block;
  margin: 15px 0;
  color: #333333;
  text-decoration: none;
  font-size: 1rem;
  transition: color 0.3s ease;
}

.side-nav a:hover {
  color: var(--accent-color);
}

/* 主内容区样式 */
.main-content {
  margin-left: 220px;
  padding: 80px 40px 40px 40px;
  max-width: 1200px;
  margin-right: auto;
}

.main-content h2, .main-content h3, .main-content h4 {
  color: var(--primary-color);
  margin-bottom: 20px;
}

.main-content p {
  margin-bottom: 20px;
}

.main-content a {
  color: var(--primary-color);
  text-decoration: none;
  transition: color 0.3s ease;
}

.main-content a:hover {
  color: var(--accent-color);
}

/* 卡片式设计 */
.grid-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 20px;
  margin-bottom: 40px;
}

.card {
  background-color: #FFFFFF;
  border-radius: 12px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  overflow: hidden;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.card:hover {
  transform: translateY(-10px);
  box-shadow: 0 10px 15px rgba(0, 0, 0, 0.2);
}

.card img {
  width: 100%;
  height: auto;
  border-bottom: 1px solid #E0E0E0;
}

.card-content {
  padding: 20px;
  color: #333333;
}

.card-content h3 {
  font-size: 1.25rem;
  margin-bottom: 10px;
}

.card-content p {
  font-size: 1rem;
  margin-bottom: 10px;
}

/* 图片样式 */
.decorative-image {
  width: 100%;
  max-width: 320px;
  border-radius: 12px;
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.decorative-image:hover {
  transform: scale(1.05);
  box-shadow: 0 8px 12px rgba(0, 0, 0, 0.2);
  cursor: pointer;
}

/* 代码块样式 */
pre {
  background-color: #F0F0F0;
  padding: 15px;
  border-radius: 8px;
  overflow-x: auto;
  margin-bottom: 20px;
}

code {
  font-family: 'Courier New', Courier, monospace;
  color: #C7254E;
}

.language-css {
  color: #0000FF;
}

/* 章节导航样式 */
.chapter-nav {
  position: sticky;
  top: var(--header-height);
  background-color: var(--secondary-color);
  padding: 20px;
  border-radius: 8px;
}

.chapter-nav ul {
  list-style: none;
}

.chapter-nav li {
  margin-bottom: 10px;
}

.chapter-nav a {
  color: var(--primary-color);
  text-decoration: none;
  transition: color 0.3s ease;
}

.chapter-nav a:hover {
  color: var(--accent-color);
}

/* 提示文本样式 */
.reference-note {
  background-color: var(--accent-color);
  color: #FFFFFF;
  padding: 15px;
  border-radius: 8px;
  text-align: center;
  margin-bottom: 40px;
  font-size: 1.2rem;
}

/* 响应式设计 */
@media (max-width: 1200px) {
  .main-content {
    padding: 80px 20px 20px 220px;
  }
}

@media (max-width: 768px) {
  .side-nav {
    display: none;
  }

  .main-content {
    margin-left: 0;
    padding: 80px 20px 20px 20px;
  }

  .grid-container {
    grid-template-columns: 1fr;
  }

  .top-nav .menu {
    flex-direction: column;
    align-items: flex-start;
  }
}

@media (max-width: 480px) {
  .top-nav {
    flex-direction: column;
    align-items: flex-start;
    height: auto;
    padding: 10px 20px;
  }

  .top-nav .menu {
    flex-direction: column;
    width: 100%;
  }

  .top-nav .menu a {
    padding: 10px 0;
    width: 100%;
    border-bottom: 1px solid #FFFFFF;
  }

  .chapter-nav {
    display: none;
  }
}

/* 动画效果 */
@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

.fade-in {
  animation: fadeIn 1.5s ease-in-out;
}

/* 按钮样式 */
.button {
  background-color: var(--accent-color);
  color: #FFFFFF;
  padding: 10px 20px;
  border: none;
  border-radius: 25px;
  cursor: pointer;
  transition: transform 0.3s ease, background-color 0.3s ease;
}

.button:hover {
  transform: scale(1.1);
  background-color: rgba(255, 111, 0, 0.8);
}

/* 折叠区域样式 */
.collapsible {
  background-color: var(--secondary-color);
  color: #333333;
  cursor: pointer;
  padding: 15px;
  width: 100%;
  border: none;
  text-align: left;
  outline: none;
  font-size: 1rem;
  transition: background-color 0.3s ease;
  border-radius: 8px;
  margin-bottom: 10px;
}

.active, .collapsible:hover {
  background-color: var(--primary-color);
  color: #FFFFFF;
}

.content {
  padding: 0 15px;
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
  background-color: #F0F0F0;
  border-radius: 8px;
  margin-bottom: 20px;
}

.content p {
  padding: 15px 0;
}