:root {
    --bg-primary: #f5f5f5;
    --bg-secondary: #e8e8e8;
    --bg-card: #ffffff;
    --text-primary: #1a1a1a;
    --text-secondary: #666666;
    --border-color: #e0e0e0;
    --accent-color: #2563eb;
    --accent-hover: #1d4ed8;
    --shadow: 0 2px 8px rgba(0,0,0,0.1);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.3s, color 0.3s;
}

/* 导航栏 */
.navbar {
    background-color: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    box-shadow: var(--shadow);
}

.navbar-container {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 20px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 64px;
    position: relative;
}

.logo {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--accent-color);
    text-decoration: none;
    letter-spacing: -0.5px;
}

.nav-menu {
    display: flex;
    gap: 30px;
    align-items: center;
    list-style: none;
    margin-left: auto;
}

.nav-menu a {
    color: var(--text-primary);
    text-decoration: none;
    font-weight: 500;
    transition: color 0.3s;
}

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

/* 汉堡菜单按钮 */
.menu-toggle {
    display: none;
    flex-direction: column;
    background: none;
    border: none;
    cursor: pointer;
    padding: 8px;
    gap: 5px;
}

.menu-toggle span {
    width: 25px;
    height: 3px;
    background-color: var(--text-primary);
    transition: all 0.3s;
    border-radius: 3px;
}

.menu-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(7px, 7px);
}

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

.menu-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(7px, -7px);
}

/* 主内容区 */
.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 40px 20px;
}

.page-title {
    font-size: 2rem;
    margin-bottom: 10px;
    font-weight: 700;
}

.page-description {
    color: var(--text-secondary);
    margin-bottom: 40px;
    font-size: 0.95rem;
}

/* 文章卡片 */
.articles-grid {
    display: grid;
    gap: 20px;
}

.article-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 24px;
    transition: transform 0.3s, box-shadow 0.3s;
    cursor: pointer;
    position: relative;
}

.article-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow);
}

.article-meta {
    color: var(--text-secondary);
    font-size: 0.8rem;
    margin-bottom: 10px;
}

.article-title {
    font-size: 1.35rem;
    margin-bottom: 12px;
    font-weight: 600;
    color: var(--text-primary);
}

.article-title a {
    color: inherit;
    text-decoration: none;
    transition: color 0.3s;
}

.article-title a::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 1;
}

.article-title a:hover {
    color: var(--accent-color);
}

.article-excerpt {
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 16px;
    font-size: 0.9rem;
}

.article-tags {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.tag {
    background-color: var(--bg-secondary);
    color: var(--text-primary);
    padding: 4px 10px;
    border-radius: 20px;
    font-size: 0.8rem;
    text-decoration: none;
    transition: background-color 0.3s;
    position: relative;
    z-index: 2;
}

.tag:hover {
    background-color: var(--accent-color);
    color: white;
}

/* 返回顶部按钮 */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    background-color: var(--accent-color);
    color: white;
    width: 50px;
    height: 50px;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    font-size: 1.5rem;
    display: none;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow);
    transition: background-color 0.3s, transform 0.3s;
}

.back-to-top:hover {
    background-color: var(--accent-hover);
    transform: scale(1.1);
}

.back-to-top.visible {
    display: flex;
}

/* 页脚 */
.footer {
    background-color: #2a2a2a;
    border-top: 1px solid #404040;
    margin-top: 60px;
    padding: 30px 20px;
    text-align: center;
    color: #cccccc;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .navbar-container {
        height: 64px;
        align-items: center;
    }

    .menu-toggle {
        display: flex;
    }

    .logo {
        flex: 1;
    }

    .nav-menu {
        position: absolute;
        top: 64px;
        left: 0;
        right: 0;
        width: 100%;
        flex-direction: column;
        gap: 0;
        margin-left: 0;
        padding: 0;
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.3s ease-in-out;
        background-color: var(--bg-card);
        border-top: 1px solid var(--border-color);
    }

    .nav-menu.active {
        max-height: 300px;
        border-top: 1px solid var(--border-color);
    }

    .nav-menu li {
        width: 100%;
        border-bottom: 1px solid var(--border-color);
    }

    .nav-menu li:last-child {
        border-bottom: none;
    }

    .nav-menu a {
        display: block;
        padding: 15px 20px;
        text-align: center;
    }

    .page-title {
        font-size: 1.6rem;
    }

    .article-card {
        padding: 18px;
    }

    .article-title {
        font-size: 1.2rem;
    }
}