:root {
    /* 主色调：深沉的血色与钢铁色 */
    --primary-dark: #8B0000;  /* 深红色 - 战争的血色 */
    --primary-light: #B22222; /* 火砖红 - 战火 */
    --secondary-dark: #2C3539; /* 钢铁灰 - 军工业与武器 */
    --secondary-light: #708090; /* 石板灰 - 战争迷雾 */
    
    /* 中性色 */
    --neutral-darkest: #121212; /* 近黑色 */
    --neutral-dark: #1E1E1E;    /* 深灰色 */
    --neutral-mid: #4A4A4A;     /* 中灰色 */
    --neutral-light: #E0E0E0;   /* 浅灰色 */
    --neutral-lightest: #F5F5F5; /* 近白色 */
    
    /* 强调色 */
    --accent-yellow: #D4AF37; /* 金色 - 历史文献的质感 */
    --accent-blue: #1C3D5A;   /* 深蓝色 - 历史的深度 */
    
    /* 文字颜色 */
    --text-dark: #121212;
    --text-light: #F5F5F5;
    
    /* 间距单位 */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2.5rem;
    --spacing-xxl: 4rem;
    
    /* 字体 */
    --font-serif: 'Noto Serif SC', serif;
    --font-sans: 'Noto Sans SC', sans-serif;
    
    /* 过渡时间 */
    --transition-fast: 0.2s;
    --transition-medium: 0.4s;
    --transition-slow: 0.8s;
}

/* 基础重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: var(--font-sans);
    line-height: 1.6;
    overflow-x: hidden;
    transition: background-color var(--transition-medium), color var(--transition-medium);
}

/* 主题样式 */
body.light-theme {
    background-color: var(--neutral-lightest);
    color: var(--text-dark);
}

body.dark-theme {
    background-color: var(--neutral-dark);
    color: var(--text-light);
}

/* 排版 */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-serif);
    font-weight: 700;
    line-height: 1.2;
}

h1 {
    font-size: clamp(2.5rem, 5vw, 4rem);
    font-weight: 900;
    letter-spacing: -0.02em;
}

h2 {
    font-size: clamp(2rem, 4vw, 3rem);
    margin-bottom: var(--spacing-lg);
}

h3 {
    font-size: clamp(1.5rem, 3vw, 2rem);
    margin-bottom: var(--spacing-md);
}

p {
    margin-bottom: var(--spacing-md);
}

a {
    text-decoration: none;
    color: inherit;
    transition: all var(--transition-fast);
}

/* 容器 */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* 移动端增加边距 */
@media (max-width: 768px) {
    .container {
        padding: 0 var(--spacing-lg);
    }
    
    .hero-content {
        padding: var(--spacing-xl) var(--spacing-lg);
    }
    
    .chapter-content {
        padding: var(--spacing-lg) var(--spacing-xl);
    }
    
    .overview {
        padding: var(--spacing-xl) var(--spacing-lg);
    }
    
    .footer {
        padding: var(--spacing-xl) var(--spacing-lg);
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 var(--spacing-xl);
    }
    
    .hero-content {
        padding: var(--spacing-xl);
    }
    
    .chapter-content {
        padding: var(--spacing-lg) var(--spacing-xl);
    }
    
    .overview {
        padding: var(--spacing-xl);
    }
    
    .footer {
        padding: var(--spacing-xl);
    }
}

/* 按钮 */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    border-radius: 0;
    font-weight: 500;
    letter-spacing: 0.05em;
    text-transform: uppercase;
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
    overflow: hidden;
    border: none;
    font-family: var(--font-sans);
}

.btn::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: currentColor;
    transform: scaleX(0);
    transform-origin: right;
    transition: transform var(--transition-medium);
}

.btn:hover::after {
    transform: scaleX(1);
    transform-origin: left;
}

.btn-primary {
    background-color: var(--primary-dark);
    color: var(--text-light);
}

.btn-primary:hover {
    background-color: var(--primary-light);
}

.btn-secondary {
    background-color: transparent;
    color: var(--text-light);
    border: 1px solid var(--text-light);
}

.btn-secondary:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

/* 英雄区 */
.hero {
    position: relative;
    height: 100vh;
    min-height: 600px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-light);
    overflow: hidden;
}

.hero-bg {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    background: linear-gradient(to right, rgba(0, 0, 0, 0.8), rgba(139, 0, 0, 0.6)), url('./images/index.jpg') no-repeat center center/cover;
}

.hero-content {
    text-align: center;
    max-width: 800px;
    padding: var(--spacing-xl);
    position: relative;
    z-index: 1;
}

.hero-subtitle {
    font-family: var(--font-serif);
    font-size: clamp(1.25rem, 2vw, 1.75rem);
    margin-bottom: var(--spacing-xl);
    font-weight: 400;
    opacity: 0.9;
}

.hero-buttons {
    display: flex;
    gap: var(--spacing-md);
    justify-content: center;
    margin-top: var(--spacing-xl);
}

/* 时间线指示器 */
.timeline-indicator {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background-color: var(--primary-dark);
    transform-origin: left;
    transform: scaleX(0);
    z-index: 1000;
}

/* 章节卡片 */
.chapter-card {
    position: relative;
    background-color: var(--neutral-lightest);
    border-radius: 0;
    overflow: hidden;
    transition: all var(--transition-medium);
    height: 100%;
    display: flex;
    flex-direction: column;
}

.dark-theme .chapter-card {
    background-color: var(--neutral-mid);
}

.chapter-card:hover {
    transform: translateY(-8px);
}

.chapter-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 0;
    background-color: var(--primary-dark);
    transition: height var(--transition-medium);
}

.chapter-card:hover::before {
    height: 100%;
}

.chapter-content {
    padding: var(--spacing-lg);
    flex-grow: 1;
    display: flex;
    flex-direction: column;
}

.chapter-title {
    font-size: 1.25rem;
    margin-bottom: var(--spacing-sm);
    font-weight: 600;
    color: var(--text-dark);
}

.dark-theme .chapter-title {
    color: var(--text-light);
}

.chapter-description {
    font-size: 0.95rem;
    color: var(--neutral-mid);
    margin-bottom: 0;
    flex-grow: 1;
}

.dark-theme .chapter-description {
    color: var(--neutral-light);
}

/* 部分标题 */
.part-title {
    position: relative;
    margin-bottom: var(--spacing-xl);
    padding-bottom: var(--spacing-sm);
    display: inline-block;
}

.part-title::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 60%;
    height: 3px;
    background-color: var(--primary-dark);
}

/* 部分容器 */
.part-container {
    margin-bottom: var(--spacing-xxl);
    opacity: 0;
    transform: translateY(30px);
    transition: opacity var(--transition-slow), transform var(--transition-slow);
}

.part-container.visible {
    opacity: 1;
    transform: translateY(0);
}

/* 网格布局 */
.grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
}

/* 概述部分 */
.overview {
    padding: var(--spacing-xl);
    border-radius: 0;
    position: relative;
    overflow: hidden;
    margin-bottom: var(--spacing-xxl);
}

.light-theme .overview {
    background-color: var(--accent-blue);
    color: var(--text-light);
}

.dark-theme .overview {
    background-color: var(--primary-dark);
    color: var(--text-light);
}

.overview::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: url('https://images.unsplash.com/photo-1580828343064-fde4fc206bc6?ixlib=rb-4.0.3&ixid=M3wxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8fA%3D%3D&auto=format&fit=crop&w=2071&q=80') no-repeat center center/cover;
    opacity: 0.1;
    z-index: -1;
}

.overview-content {
    position: relative;
    z-index: 1;
    max-width: 800px;
    margin: 0 auto;
}

/* 页脚 */
.footer {
    padding: var(--spacing-xl) 0;
    position: relative;
}

.light-theme .footer {
    background-color: var(--secondary-dark);
    color: var(--text-light);
}

.dark-theme .footer {
    background-color: var(--neutral-darkest);
    color: var(--text-light);
}

.footer-content {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xl);
}

@media (min-width: 768px) {
    .footer-content {
        flex-direction: row;
        justify-content: space-between;
        align-items: flex-start;
    }
}

.footer-info h3 {
    margin-bottom: var(--spacing-md);
    font-size: 1.25rem;
}

.footer-info p {
    margin-bottom: var(--spacing-sm);
    opacity: 0.8;
}

.footer-copyright {
    text-align: center;
}

@media (min-width: 768px) {
    .footer-copyright {
        text-align: right;
    }
}

/* 主题切换按钮 */
.theme-toggle {
    position: fixed;
    bottom: var(--spacing-xl);
    right: var(--spacing-md);
    z-index: 100;
    background: rgba(0, 0, 0, 0.3);
    border: 1px solid rgba(255, 255, 255, 0.2);
    cursor: pointer;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    transition: all var(--transition-fast);
}

.theme-toggle:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

.theme-toggle svg {
    width: 24px;
    height: 24px;
    fill: var(--text-light);
    transition: transform var(--transition-medium);
}

.light-theme .theme-toggle svg {
    fill: var(--text-dark);
}

.theme-toggle:hover svg {
    transform: rotate(45deg);
}

/* 滚动指示器 */
.scroll-indicator {
    position: absolute;
    bottom: var(--spacing-xl);
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    flex-direction: column;
    align-items: center;
    color: var(--text-light);
    opacity: 0.8;
    transition: opacity var(--transition-fast);
    cursor: pointer;
}

.scroll-indicator:hover {
    opacity: 1;
}

.scroll-indicator span {
    font-size: 0.875rem;
    margin-bottom: var(--spacing-sm);
    letter-spacing: 0.1em;
    text-transform: uppercase;
}

.scroll-indicator svg {
    width: 24px;
    height: 24px;
    animation: bounce 2s infinite;
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        transform: translateY(0);
    }
    40% {
        transform: translateY(-10px);
    }
    60% {
        transform: translateY(-5px);
    }
}

/* 导航菜单 */
.nav-menu {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    padding: var(--spacing-md);
    z-index: 90;
    transition: background-color var(--transition-medium);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-menu.scrolled {
    background-color: rgba(30, 30, 30, 0.95);
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.1);
}

.light-theme .nav-menu.scrolled {
    background-color: rgba(245, 245, 245, 0.95);
}

.nav-logo {
    font-family: var(--font-serif);
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--text-light);
}

.light-theme .nav-logo {
    color: var(--text-dark);
}

.nav-links {
    display: none;
}

@media (min-width: 768px) {
    .nav-links {
        display: flex;
        gap: var(--spacing-lg);
    }
}

.nav-link {
    font-size: 0.9rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    position: relative;
    color: var(--text-light);
}

.light-theme .nav-link {
    color: var(--text-dark);
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: var(--primary-dark);
    transform: scaleX(0);
    transform-origin: right;
    transition: transform var(--transition-fast);
}

.nav-link:hover::after {
    transform: scaleX(1);
    transform-origin: left;
}

/* 移动菜单按钮 */
.menu-toggle {
    display: block;
    width: 30px;
    height: 20px;
    position: relative;
    cursor: pointer;
    z-index: 100;
}

@media (min-width: 768px) {
    .menu-toggle {
        display: none;
    }
}

.menu-toggle span {
    display: block;
    position: absolute;
    height: 2px;
    width: 100%;
    background-color: var(--text-light);
    border-radius: 2px;
    transition: all var(--transition-fast);
}

.light-theme .menu-toggle span {
    background-color: var(--text-dark);
}

.menu-toggle span:nth-child(1) {
    top: 0;
}

.menu-toggle span:nth-child(2) {
    top: 9px;
}

.menu-toggle span:nth-child(3) {
    top: 18px;
}

.menu-toggle.active span:nth-child(1) {
    transform: rotate(45deg);
    top: 9px;
}

.menu-toggle.active span:nth-child(2) {
    opacity: 0;
}

.menu-toggle.active span:nth-child(3) {
    transform: rotate(-45deg);
    top: 9px;
}

/* 移动菜单 */
.mobile-menu {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100vh;
    background-color: var(--neutral-dark);
    z-index: 95;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    transform: translateX(-100%);
    transition: transform var(--transition-medium);
}

.light-theme .mobile-menu {
    background-color: var(--neutral-lightest);
}

.mobile-menu.active {
    transform: translateX(0);
}

.mobile-links {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
    text-align: center;
}

.mobile-link {
    font-size: 1.5rem;
    font-weight: 500;
    color: var(--text-light);
    position: relative;
    display: inline-block;
}

.light-theme .mobile-link {
    color: var(--text-dark);
}

.mobile-link::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: var(--primary-dark);
    transform: scaleX(0);
    transform-origin: right;
    transition: transform var(--transition-fast);
}

.mobile-link:hover::after {
    transform: scaleX(1);
    transform-origin: left;
}

/* 年代标记 */
.year-marker {
    position: absolute;
    left: 0;
    width: 60px;
    height: 24px;
    background-color: var(--primary-dark);
    color: var(--text-light);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.05em;
}

/* 战争进度指示器 */
.war-progress {
    position: fixed;
    left: var(--spacing-md);
    top: 50%;
    transform: translateY(-50%);
    display: flex;
    flex-direction: column;
    gap: 30px;
    z-index: 80;
}

@media (max-width: 1024px) {
    .war-progress {
        display: none;
    }
}

.progress-point {
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background-color: var(--neutral-mid);
    position: relative;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.progress-point::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background-color: var(--primary-dark);
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.progress-point:hover,
.progress-point.active {
    background-color: var(--neutral-light);
}

.progress-point:hover::before,
.progress-point.active::before {
    opacity: 1;
}

.progress-point::after {
    content: attr(data-year);
    position: absolute;
    left: 24px;
    top: 50%;
    transform: translateY(-50%);
    white-space: nowrap;
    font-size: 0.75rem;
    color: var(--neutral-mid);
    opacity: 0;
    transition: opacity var(--transition-fast);
}

.progress-point:hover::after,
.progress-point.active::after {
    opacity: 1;
}

.progress-line {
    position: absolute;
    top: 12px;
    left: 6px;
    width: 1px;
    height: calc(100% - 24px);
    background-color: var(--neutral-mid);
    z-index: -1;
}

/* 文本大小辅助类 */
.text-lg {
    font-size: 1.125rem;
}

/* 链接样式 */
.footer-link {
    color: var(--accent-yellow);
    transition: color var(--transition-fast);
}

.footer-link:hover {
    color: var(--primary-light);
    text-decoration: underline;
}