header {
    position: fixed;
    width: 100%;
    top: 0;
    left: 0;
    z-index: 999;
    background-color: #FFF;
    box-shadow: 0 0 30px 10px rgba(0, 0, 0, .12);
    text-align: center;
}


/* section1: nav */
header>div:first-child {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    align-items: center;
    padding: 10px 25px;
    box-shadow: 0 0 30px 10px rgba(0, 0, 0, .12);
}

/* left nav */
header>div:first-child img {
    height: 30px;
    display: block;
}
/* right nav */
header>div:first-child li {
    font-weight: bold;
    padding: 0 5px;
    display: inline-block;
}
header>div:first-child li:last-child {
    padding-right: 0;
}


/* section2 show: cai liao shi yan ji*/
header>div:last-child {
    max-height: 400px;
    padding: 20px 25px;
    display: none;
    overflow: auto;
}

header>div:last-child img {
    height: 200px;
}

header>div:last-child>ul {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    text-align: center;
}

header>div:last-child>ul img {
    transition: scale 0.5s;
}

header>div:last-child>ul img:hover {
    scale: 1.1;
}

.placeholder-section {
    height: 50px;
}