body,
html {
    margin: 0;
    padding: 0;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    /* 添加这一行来使得内容垂直排列 */
}

span {
    color: white;
    /* 将所有span元素的文本颜色设置为白色 */
}

.top-div {
    position: relative;
    top: 0;
    width: 100%;
    height: 50px;
    background-image: url('top.jpg');
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center;
    opacity: 0.5;
    display: flex;
    justify-content: space-between;
    align-items: center;
    color: white;
}

.left-text {
    text-align: left;
    margin-left: 10px;
}

.right-text {
    text-align: right;
    margin-right: 10px;
}

.centered-div {
    height: 100vh;
    width: calc(100vh * 9 / 16);
    background-image: url('bg.jpg');
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center;
    display: flex;
    flex-direction: column;
    /* 添加这一行来使得内容垂直排列 */
    justify-content: space-between;
    /* 确保top, middle, bottom分布在顶部、中间、底部 */
}

.middle-div {
    position: relative;
    transform: none;
    /* 移除transform属性 */
    top: auto;
    /* 移除top属性 */
    left: auto;
    /* 移除left属性 */
    width: 100%;
    height: 200px;
    /* background-image: url('desc.png'); */
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center;
}

.middle-content {
    position: relative;
    transform: none;
    /* 移除transform属性 */
    top: auto;
    /* 移除top属性 */
    left: auto;
    /* 移除left属性 */
    width: 100%;
}

.middle-text-content {
    background-color: #FFFFE0;
    /* 淡黄色 */
}

.bottom-div {
    position: relative;
    bottom: 0;
    width: 100%;
    height: 100px;
    background-image: url('bottom.png');
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center;
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    align-items: center;
    color: white;
}

.bottom-div span {
    flex: 1;
    /* 前三个span共享空间 */
    text-align: center;
    /* 文本居中 */
}

.bottom-div span:last-child {
    flex-basis: 100%;
    /* 第四个span占据整行 */
    text-align: center;
    /* 文本居中 */
}