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

body {
    font-family: 'Microsoft YaHei', Arial, sans-serif;
    line-height: 1.6;
    color: #333;
    background-color: #f8f9fa;
}

/* 头部样式 */
header {
    background-color: #fff;
    box-shadow: 0 2px 5px rgba(0,0,0,0.1);
    position: sticky;
    top: 0;
    z-index: 100;
}

.site-title {
    text-align: center;
    padding: 20px;
    font-size: 2rem;
    color: #ff6b6b;
}

/* 导航栏样式 */
nav {
    background-color: #4a4a4a;
}

.nav-container {
    display: flex;
    justify-content: center;
    max-width: 1200px;
    margin: 0 auto;
}

.nav-item {
    padding: 15px 30px;
    color: white;
    text-decoration: none;
    display: block;
    transition: background-color 0.3s;
}

.nav-item:hover {
    background-color: #5a5a5a;
}

.nav-item.active {
    background-color: #ff6b6b;
}

/* 主要内容区域 */
main {
    max-width: 1200px;
    margin: 20px auto;
    padding: 0 20px;
}

/* 页面显示控制 */
.page-active {
    display: block !important;
}

/* 返回按钮 */
.back-button {
    display: inline-block;
    background-color: #4a4a4a;
    color: white;
    padding: 10px 20px;
    border-radius: 5px;
    text-decoration: none;
    margin-bottom: 20px;
    transition: background-color 0.3s;
}

.back-button:hover {
    background-color: #5a5a5a;
}

/* 返回顶部按钮样式 */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background-color: transparent;
    color: #4da6ff;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    text-decoration: none;
    cursor: pointer;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
    transition: all 0.3s ease;
    opacity: 0;
    visibility: hidden;
    border: 2px solid #4da6ff;
    z-index: 100;
}

.back-to-top::before {
    content: '⬆️';
    display: inline-block;
    line-height: 1;
    vertical-align: middle;
    font-size: larger;
}

.back-to-top:hover {
    background-color: rgba(77, 166, 255, 0.1);
    transform: translateY(-5px);
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
    color: #3399ff;
    border-color: #3399ff;
}

.back-to-top.show {
    opacity: 1;
    visibility: visible;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .site-title {
        font-size: 1.5rem;
        padding: 15px;
    }

    .nav-item {
        padding: 12px 15px;
        font-size: 0.9rem;
    }
    
    .back-to-top {
        bottom: 20px;
        right: 20px;
        width: 45px;
        height: 45px;
        font-size: 18px;
    }
}