/* 全局基础样式 */
body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f5f5f5;
}

header {
    background-color: #333;
    color: #fff;
    padding: 10px 20px;
}

.logo {
    float: left;
    font-size: 24px;
}

nav {
    float: right;
}

nav ul {
    list-style: none;
    margin: 0;
    padding: 0;
}

nav ul li {
    display: inline-block;
    margin-left: 20px;
}

nav ul li a {
    color: #fff;
    text-decoration: none;
}

nav ul li a.active {
    font-weight: bold;
}

main {
    padding: 20px;
}

footer {
    text-align: center;
    padding: 10px;
    background-color: #333;
    color: #fff;
}

.btn {
    display: inline-block;
    background-color: #f00;
    color: #fff;
    padding: 8px 16px;
    text-decoration: none;
    border-radius: 4px;
}