html, body {
    height: 100%;
    margin: 0;
    padding: 0;
}

/*整个DIV*/
.All {
    display: flex;
    flex-direction: column;
    min-height: 100vh; /*这个要100vh撑开首个div*/
    background-image: url(../images/bg7.gif);
    transition: background-image 0.3s;
    background-size: cover;
    background-position: center;
}

/*头和尾（显示个人logo）*/
.Header {
    height: 80px;
    background-color: rgba(0, 0, 0,0.8);
    font-size: 24px;
    position: fixed;
    top: -80px; /*    默认隐藏（假设高度为80px） */
    left: 0;
    width: 100%;
    color: white;
    display: flex;
    align-items: center;
    justify-content: space-between; 
    padding: 0px 20px; /* 给头部留点内边距 */
    transition: top 0.4s ease; /*状态变化0.4*/
    z-index: 999; /*最顶部*/
}

    .Header.show {
        top: 0; /*显示出来*/
    }

.Logo img {
    height: 60px;
    width: auto;
    transform: translateY(5px); /* 调整图片位置 */
}

.portal{
    display: flex;
}

.portal img{
    height: 60px;
    width:  auto;
    transform: translateX(-50px);
}


/*中间页*/
.Body {
    flex: 1; /* 关键，让它占据剩余空间 */
    display: flex;
    flex-direction: row;
    text-align: center;
    font-size: 24px;
    background-size: cover;
    background-position: center;
}