/* 
整体样式设置
设置网页的基础样式，包括字体、背景色、主色调等，确保整体色彩运用丰富且协调，遵循黄金比例配色法则。
*/
body {
    margin: 0;
    padding: 0;
    font-family: 'Roboto', sans-serif;
    font-size: 16px;
    color: #ffffff;
    background: linear-gradient(135deg, #0B3D91 70%, #76B5C5 25%, #FFA500 5%);
    transition: background 0.5s ease;
}

/* 
导航栏样式
固定在顶部，使用半透明背景，包含多级菜单，增加科技感与互动性。
*/
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(11, 61, 145, 0.9);
    padding: 20px 40px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 1000;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.navbar ul {
    list-style: none;
    display: flex;
    gap: 30px;
}

.navbar ul li {
    position: relative;
}

.navbar ul li a {
    color: #ffffff;
    text-decoration: none;
    font-size: 18px;
    transition: color 0.3s ease;
}

.navbar ul li a:hover {
    color: #FFA500;
}

.navbar ul li ul {
    position: absolute;
    top: 60px;
    left: 0;
    background: rgba(255, 255, 255, 0.1);
    padding: 15px;
    border-radius: 8px;
    display: none;
    flex-direction: column;
}

.navbar ul li:hover ul {
    display: flex;
    animation: dropdown 0.3s ease forwards;
}

@keyframes dropdown {
    from { opacity: 0; transform: translateY(-10px); }
    to { opacity: 1; transform: translateY(0); }
}

/* 
主内容区样式
采用模块化卡片式布局，使用Flexbox和Grid布局，确保响应式设计和视觉层次分明。
*/
.main {
    padding: 120px 60px 60px 60px;
    display: grid;
    grid-template-columns: 1fr 3fr;
    gap: 40px;
}

.sidebar {
    background: rgba(255, 255, 255, 0.1);
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.sidebar h2 {
    font-size: 24px;
    margin-bottom: 20px;
    color: #FFA500;
}

.sidebar ul {
    list-style: none;
    padding: 0;
}

.sidebar ul li {
    margin-bottom: 15px;
}

.sidebar ul li a {
    color: #ffffff;
    text-decoration: none;
    font-size: 18px;
    transition: color 0.3s ease;
}

.sidebar ul li a:hover {
    color: #FFA500;
}

.content {
    display: flex;
    flex-direction: column;
    gap: 40px;
}

.article {
    background: rgba(255, 255, 255, 0.1);
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.article h2, .article h3, .article h4 {
    color: #FFA500;
}

.article p {
    line-height: 1.8;
    margin-bottom: 20px;
}

.article pre {
    background: #0B3D91;
    padding: 15px;
    border-radius: 8px;
    overflow-x: auto;
}

.article pre code {
    color: #76B5C5;
    font-family: 'Courier New', Courier, monospace;
}

.image-gallery {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 20px;
}

.image-gallery img {
    width: 100%;
    height: auto;
    border-radius: 15px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.3);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.image-gallery img:hover {
    transform: scale(1.05);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.5);
}

/* 
响应式设计
确保网页在不同设备上的良好展示，使用媒体查询调整布局和元素尺寸。
*/
@media (max-width: 1200px) {
    .main {
        grid-template-columns: 1fr 2fr;
    }
}

@media (max-width: 900px) {
    .main {
        grid-template-columns: 1fr;
    }

    .sidebar {
        order: 2;
    }

    .content {
        order: 1;
    }
}

@media (max-width: 600px) {
    .navbar {
        flex-direction: column;
        align-items: flex-start;
    }

    .navbar ul {
        flex-direction: column;
        gap: 10px;
    }

    .main {
        padding: 100px 20px 20px 20px;
    }
}

/* 
按钮样式
设计悬停效果，增加互动感，使用渐变色和阴影。
*/
.button {
    background: linear-gradient(45deg, #FFA500, #FF8C00);
    border: none;
    padding: 15px 30px;
    border-radius: 25px;
    color: #ffffff;
    font-size: 16px;
    cursor: pointer;
    transition: transform 0.3s ease, background 0.3s ease;
}

.button:hover {
    transform: scale(1.1);
    background: linear-gradient(45deg, #FF8C00, #FFA500);
}

/* 
折叠区域样式
用于次要信息的隐藏与展开，提升页面整洁度。
*/
.collapsible {
    background: rgba(255, 255, 255, 0.1);
    color: #ffffff;
    cursor: pointer;
    padding: 15px;
    width: 100%;
    border: none;
    text-align: left;
    outline: none;
    font-size: 18px;
    border-radius: 8px;
    transition: background 0.3s ease;
}

.collapsible:hover {
    background: rgba(255, 165, 0, 0.2);
}

.content-collapsible {
    padding: 0 15px;
    display: none;
    background: rgba(255, 255, 255, 0.05);
    overflow: hidden;
    border-radius: 0 0 8px 8px;
}

.active + .content-collapsible {
    display: block;
    animation: fadeIn 0.5s ease;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

/* 
章节导航样式
用于快速定位到指定内容区域，具有明显的视觉风格，不遮挡内容。
*/
.chapter-nav {
    position: sticky;
    top: 100px;
    background: rgba(11, 61, 145, 0.9);
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

.chapter-nav ul {
    list-style: none;
    padding: 0;
}

.chapter-nav ul li {
    margin-bottom: 15px;
}

.chapter-nav ul li a {
    color: #ffffff;
    text-decoration: none;
    font-size: 16px;
    transition: color 0.3s ease;
}

.chapter-nav ul li a:hover {
    color: #FFA500;
}

/* 
图片描述属性设置为空
确保装饰性图片的描述属性为空，提升页面的无障碍性。
*/
img {
    alt: "";
}