* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
}

/* 通用标题样式 */
h1 {
    font-size: 2.5em;
    color: #2c3e50;
    margin-bottom: 0.5em;
}

h2 {
    font-size: 1.8em;
    color: #34495e;
    margin-top: 1.5em;
    margin-bottom: 0.8em;
}

h3 {
    font-size: 1.3em;
    color: #2c3e50;
    margin-top: 1.2em;
    margin-bottom: 0.6em;
}

.container {
    max-width: 1400px;
    margin: 0 auto;
    background: white;
    border-radius: 15px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
    overflow: hidden;
}

header {
    background: linear-gradient(135deg, #2c3e50 0%, #3498db 100%);
    color: white;
    padding: 40px 30px;
    text-align: center;
}

header h1 {
    font-size: 2.8em;
    margin-bottom: 10px;
    color: white;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
}

header .title {
    font-size: 2.8em;
    margin-bottom: 10px;
    color: white;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
    font-weight: bold;
}

header p {
    font-size: 1.2em;
    opacity: 0.9;
}

/* 导航菜单样式 */
.nav-menu {
    background: #34495e;
    padding: 0;
    position: relative;
    z-index: 1000;
}

.nav-menu ul {
    list-style: none;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
}

.nav-menu > ul > li {
    position: relative;
}

/* 一级菜单 */
.nav-menu > ul > li > a {
    display: block;
    padding: 18px 30px;
    color: white;
    text-decoration: none;
    font-size: 1.1em;
    font-weight: 600;
    transition: all 0.3s ease;
    position: relative;
    border-right: 1px solid rgba(255, 255, 255, 0.1);
}

.nav-menu > ul > li:last-child > a {
    border-right: none;
}

.nav-menu > ul > li > a:hover {
    background: #3498db;
    color: white;
}

.nav-menu > ul > li > a::after {
    content: "";
    display: inline-block;
    width: 0;
    height: 0;
    border-left: 4px solid transparent;
    border-right: 4px solid transparent;
    border-top: 5px solid white;
    margin-left: 8px;
    vertical-align: middle;
    opacity: 0.7;
}

/* 二级菜单 */
.submenu {
    position: absolute;
    top: 100%;
    left: 0;
    background: white;
    min-width: 350px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all 0.3s ease;
    border-radius: 0 0 10px 10px;
    padding: 10px 0;
    z-index: 1001;
}

.nav-menu > ul > li:hover .submenu {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.submenu-item {
    display: block;
    padding: 15px 25px;
    color: #333;
    text-decoration: none;
    transition: all 0.2s ease;
    border-bottom: 1px solid #f0f0f0;
    position: relative;
}

.submenu-item:last-child {
    border-bottom: none;
}

.submenu-item:hover {
    background: #f8f9fa;
    padding-left: 35px;
    color: #3498db;
}

.submenu-item-number {
    display: inline-block;
    background: #3498db;
    color: white;
    width: 28px;
    height: 28px;
    border-radius: 50%;
    text-align: center;
    line-height: 28px;
    font-weight: bold;
    font-size: 0.85em;
    margin-right: 12px;
    vertical-align: middle;
}

.submenu-item-content {
    display: inline-block;
    vertical-align: middle;
}

.submenu-item-title {
    font-weight: 600;
    font-size: 1em;
    margin-bottom: 3px;
    color: #2c3e50;
}

.submenu-item-description {
    font-size: 0.85em;
    color: #666;
    line-height: 1.3;
}

/* 内容区域 */
.content {
    padding: 60px 40px;
    text-align: center;
    min-height: 400px;
}

.welcome-message {
    max-width: 800px;
    margin: 0 auto;
    text-align: left !important;
}

.content .welcome-message {
    text-align: left;
}

.welcome-message h2 {
    font-size: 1.8em;
    color: #2c3e50;
    margin-bottom: 20px;
}

.welcome-message p {
    font-size: 1.2em;
    color: #666;
    line-height: 1.8;
    margin-bottom: 30px;
}

/* 内容区域的列表样式 */
.welcome-message ul,
.content ul {
    margin-left: 1.5em;
    margin-bottom: 1.2em;
    padding-left: 0.5em;
}

.welcome-message li,
.content li {
    margin-bottom: 0.5em;
    line-height: 1.6;
}

.instruction {
    background: #f8f9fa;
    padding: 25px;
    border-radius: 10px;
    border-left: 4px solid #3498db;
    margin-top: 30px;
    text-align: left;
}

.instruction h3 {
    color: #2c3e50;
    margin-bottom: 10px;
    font-size: 1.3em;
}

.instruction p {
    color: #666;
    font-size: 1em;
    margin: 0;
}

footer {
    background: #2c3e50;
    color: white;
    text-align: center;
    padding: 20px;
    font-size: 0.9em;
}

/* 文章内容页面样式 */
body.article-page {
    background-color: #f9f9f9;
    padding: 20px;
}

body.article-page .container {
    max-width: 900px;
    background-color: white;
    padding: 40px;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

body.article-page h1 {
    color: #2c3e50;
    font-size: 2.5em;
    margin-bottom: 0.5em;
    border-bottom: 3px solid #3498db;
    padding-bottom: 10px;
}

body.article-page h2 {
    color: #34495e;
    font-size: 1.8em;
    margin-top: 1.5em;
    margin-bottom: 0.8em;
    border-left: 4px solid #3498db;
    padding-left: 15px;
}

body.article-page h3 {
    color: #34495e;
    font-size: 1.3em;
    margin-top: 1.2em;
    margin-bottom: 0.6em;
}

body.article-page p {
    margin-bottom: 1.2em;
    text-align: justify;
}

body.article-page strong {
    color: #2980b9;
}

/* 响应式设计 */
@media (max-width: 768px) {
    header h1 {
        font-size: 2em;
    }
    
    header .title {
        font-size: 2em;
    }
    
    .nav-menu > ul {
        flex-direction: column;
    }
    
    .nav-menu > ul > li > a {
        border-right: none;
        border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    }
    
    .submenu {
        position: static;
        opacity: 1;
        visibility: visible;
        transform: none;
        box-shadow: none;
        background: #2c3e50;
        border-radius: 0;
        padding: 0;
        display: none;
    }
    
    .nav-menu > ul > li:hover .submenu,
    .nav-menu > ul > li.active .submenu {
        display: block;
    }
    
    .submenu-item {
        color: white;
        border-bottom-color: rgba(255, 255, 255, 0.1);
    }
    
    .submenu-item:hover {
        background: rgba(255, 255, 255, 0.1);
        color: white;
    }
    
    .submenu-item-title {
        color: white;
    }
    
    .submenu-item-description {
        color: rgba(255, 255, 255, 0.8);
    }
    
    .content {
        padding: 30px 20px;
    }
    
    .welcome-message h2 {
        font-size: 1.8em;
    }
    
    body.article-page .container {
        padding: 20px;
    }
    
    body.article-page h1 {
        font-size: 2em;
    }
    
    body.article-page h2 {
        font-size: 1.5em;
    }
    
    body.article-page h3 {
        font-size: 1.1em;
    }
    
    h1 {
        font-size: 2em;
    }
    
    h2 {
        font-size: 1.5em;
    }
    
    h3 {
        font-size: 1.1em;
    }
}