/* 全局样式设置 */
:root {
    --primary-color: #1E3A8A; /* 主色调 */
    --secondary-color: #3B82F6; /* 辅色调 */
    --accent-color: #FFA500; /* 点缀色 */
    --background-color: #2C3E50; /* 页面背景色 */
    --text-color: #ECF0F1; /* 正文字体颜色 */
    --font-family-primary: 'Roboto', sans-serif; /* 主字体 */
    --font-family-secondary: 'Lato', sans-serif; /* 辅字体 */
}

/* 重置默认样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: var(--font-family-secondary);
    color: var(--text-color);
    background-color: var(--background-color);
    line-height: 1.6;
    font-size: 16px;
}

/* 导航栏样式 */
nav {
    position: fixed;
    top: 0;
    width: 100%;
    background-color: var(--primary-color);
    display: flex;
    justify-content: center;
    padding: 20px 0;
    z-index: 1000;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

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

nav a {
    color: #FFFFFF;
    text-decoration: none;
    font-family: var(--font-family-primary);
    font-size: 18px;
    transition: color 0.3s ease;
}

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

/* 章节导航样式 */
.section-nav {
    position: fixed;
    top: 80px;
    left: 20px;
    background-color: rgba(255, 255, 255, 0.1);
    padding: 15px;
    border-radius: 8px;
}

.section-nav ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.section-nav a {
    color: var(--text-color);
    text-decoration: none;
    font-size: 16px;
    transition: color 0.3s ease;
}

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

/* 主要内容区块样式 */
.section {
    padding: 100px 20px;
    max-width: 1200px;
    margin: 0 auto;
}

.section:nth-child(even) {
    background: linear-gradient(135deg, #1E3A8A, #3B82F6);
}

.section h2, .section h3, .section h4 {
    font-family: var(--font-family-primary);
    color: #FFFFFF;
    margin-bottom: 20px;
}

.section p {
    margin-bottom: 20px;
    font-size: 17px;
}

.section img {
    width: 100%;
    max-width: 320px;
    border-radius: 12px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.2);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.section img:hover {
    transform: scale(1.05);
    box-shadow: 0 8px 16px rgba(0,0,0,0.3);
}

/* 按钮样式 */
.button {
    background-color: var(--accent-color);
    color: #FFFFFF;
    padding: 12px 24px;
    border: none;
    border-radius: 6px;
    font-size: 16px;
    cursor: pointer;
    transition: background-color 0.3s ease, transform 0.3s ease;
}

.button:hover {
    background-color: darkorange;
    transform: translateY(-3px);
}

/* 加载进度条样式 */
.progress-bar {
    width: 0%;
    height: 4px;
    background-color: var(--secondary-color);
    position: fixed;
    top: 0;
    left: 0;
    animation: load 3s forwards;
}

@keyframes load {
    from { width: 0%; }
    to { width: 100%; }
}

.progress-bar.complete {
    background-color: var(--accent-color);
    animation: none;
    width: 100%;
}

/* 聊天窗口样式 */
.chat-widget {
    position: fixed;
    bottom: 20px;
    right: 20px;
    width: 60px;
    height: 60px;
    background-color: var(--secondary-color);
    border-radius: 50%;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    cursor: pointer;
    transition: transform 0.3s ease;
}

.chat-widget:hover {
    transform: scale(1.1);
}

.chat-widget::before {
    content: '💬';
    font-size: 24px;
    color: #FFFFFF;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

.chat-popup {
    display: none;
    position: fixed;
    bottom: 90px;
    right: 20px;
    width: 300px;
    max-width: 80%;
    background-color: #FFFFFF;
    border: 1px solid #ddd;
    border-radius: 8px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    animation: fadeIn 0.5s ease;
}

.chat-popup.active {
    display: block;
}

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

/* 数据可视化样式 */
.chart {
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: #FFFFFF;
    border: 1px solid #ddd;
    border-radius: 8px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease;
}

.chart:hover {
    transform: scale(1.05);
}

/* 模块化布局样式 */
.module {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    padding: 40px 0;
}

.module-item {
    background-color: #FFFFFF;
    border: 1px solid #eee;
    border-radius: 8px;
    padding: 20px;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.module-item:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.2);
}

/* 折叠区域样式 */
.collapsible {
    background-color: var(--primary-color);
    color: #FFFFFF;
    cursor: pointer;
    padding: 18px;
    width: 100%;
    border: none;
    text-align: left;
    outline: none;
    font-size: 18px;
    transition: background-color 0.3s ease;
    border-radius: 6px;
}

.collapsible:hover {
    background-color: darkblue;
}

.content {
    padding: 0 18px;
    display: none;
    background-color: var(--background-color);
    overflow: hidden;
    border-radius: 6px;
}

.content p {
    margin: 15px 0;
}

/* 鼠标悬停图片效果 */
.image-gallery {
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
}

.image-gallery img {
    width: 100%;
    max-width: 320px;
    border-radius: 12px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.2);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.image-gallery img:hover {
    transform: scale(1.05);
    box-shadow: 0 8px 16px rgba(0,0,0,0.3);
}

/* 响应式设计 */
@media (max-width: 1920px) {
    body {
        font-size: 17px;
    }
}

@media (max-width: 768px) {
    nav ul {
        flex-direction: column;
        align-items: center;
    }

    .section-nav {
        display: none;
    }
}

@media (max-width: 480px) {
    .section {
        padding: 80px 10px;
    }

    nav a {
        font-size: 16px;
    }
}