* {
    box-sizing: border-box; /* 添加盒子模型 */
}

html, body {
    height: 100%; /* 使html和body充满整个视口 */
    margin: 0;
}

body {
    font-family: Arial, sans-serif;
    line-height: 1.6;
    display: flex;
    flex-direction: column; /* 垂直排列子元素 */
}

header {
    background: #333;
    color: #fff;
    padding: 10px 0;
    text-align: center;
}

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

nav ul li {
    display: inline;
    margin: 0 15px;
}

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

main {
    flex: 1; /* 使main区域充满剩余空间 */
    width: 960px;
    margin: 20px auto;
    padding: 0 20px;
}

.content-block {
    padding: 20px;
    border: 1px solid #ccc;
    margin: 20px 0;
    display: block; /* 默认显示 */
}

footer {
    text-align: center;
    padding: 10px 0;
    background: #333;
    color: #fff;
}