/* 全局变量定义 */
:root {
    /* 主色调 - 70% */
    --main-brown: #5D4037;
    --light-beige: #F5F5DC;
    --olive-green: #808000;
    
    /* 辅助色 - 25% */
    --modern-blue: #2196F3;
    --silver: #C0C0C0;
    
    /* 点缀色 - 5% */
    --accent-color: #FF5722;
    
    /* 字体设置 */
    --font-family-serif: 'Georgia', serif;
    --font-family-sans: 'Helvetica Neue', Helvetica, Arial, sans-serif;
    
    /* 渐变色 */
    --background-gradient: linear-gradient(to bottom, var(--light-beige), var(--olive-green));
}

/* 全局样式 */
body {
    margin: 0;
    padding: 0;
    background: var(--background-gradient);
    color: var(--main-brown);
    font-family: var(--font-family-sans);
    line-height: 1.6;
}

/* 导航栏样式 */
nav {
    background-color: var(--main-brown);
    padding: 15px 20px;
    position: fixed;
    top: 0;
    width: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 1000;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

nav a {
    color: white;
    text-decoration: none;
    margin: 0 10px;
    font-size: 1.2em;
    transition: color 0.3s ease;
}

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

/* 主内容容器 */
.container {
    display: grid;
    grid-template-areas:
        "header"
        "main"
        "footer";
    grid-gap: 20px;
    padding: 100px 20px 20px 20px; /* 顶部留出导航栏空间 */
    max-width: 1200px;
    margin: 0 auto;
}

/* 文章样式 */
article {
    grid-area: main;
    background-color: rgba(255, 255, 255, 0.9);
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

/* 文章标题 */
article h2, article h3, article h4 {
    color: var(--main-brown);
    text-shadow: 1px 1px 2px var(--silver);
    font-family: var(--font-family-serif);
}

/* 段落样式 */
article p {
    font-size: 16px;
    margin-bottom: 15px;
}

/* 代码块样式 */
article pre {
    background-color: #272822;
    color: #f8f8f2;
    padding: 15px;
    border-radius: 5px;
    overflow-x: auto;
    font-family: 'Courier New', Courier, monospace;
    margin-bottom: 20px;
}

article code {
    color: #66d9ef;
}

/* 图片样式 */
article img {
    max-width: 100%;
    height: auto;
    border-radius: 10px;
    box-shadow: 0 4px 6px rgba(0,0,0,0.2);
    transition: transform 0.3s ease;
    margin: 20px 0;
}

article img:hover {
    transform: scale(1.05);
}

/* 互动按钮样式 */
.button {
    background: var(--main-brown);
    color: white;
    padding: 10px 20px;
    border: none;
    border-radius: 5px;
    text-decoration: none;
    display: inline-block;
    transition: background 0.3s ease, transform 0.3s ease;
    cursor: pointer;
}

.button:hover {
    background: var(--modern-blue);
    transform: scale(1.05);
}

/* 折叠区域样式 */
.details {
    margin: 10px 0;
}

summary {
    font-weight: bold;
    cursor: pointer;
}

details[open] summary::after {
    content: "▲";
    float: right;
}

summary::after {
    content: "▼";
    float: right;
}

/* CSS3 示例代码块样式 */
.code-example {
    background-color: #f0f0f0;
    padding: 15px;
    border-left: 5px solid var(--modern-blue);
    margin: 20px 0;
    font-family: 'Courier New', Courier, monospace;
    overflow-x: auto;
}

/* 响应式设计 */
@media (max-width: 768px) {
    nav {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .container {
        padding: 120px 10px 10px 10px;
    }
    
    article {
        padding: 15px;
    }
}

@media (min-width: 769px) and (max-width: 1200px) {
    .container {
        padding: 110px 15px 15px 15px;
    }
    
    article {
        padding: 18px;
    }
}

/* 提示信息样式 */
.alert {
    background: var(--accent-color);
    color: white;
    padding: 10px;
    text-align: center;
    border-radius: 5px;
    margin-bottom: 20px;
    font-size: 1.1em;
    font-weight: bold;
}

/* 跨设备适配 */
@media (max-width: 480px) {
    nav a {
        font-size: 1em;
        margin: 5px 0;
    }
    
    .button {
        padding: 8px 16px;
    }
}