body{
    background-color: #1c1919;
    background-attachment:fixed ;
    margin:0;
}
body::before{
    content:"";
    position: fixed;
    top: 80px;
    left:0;
    width:100vw;
    height:80vh;
    background-image: url('../picture4.png');
    background-repeat: no-repeat;
    background-size:100% 100%;
    opacity:0.4;
    z-index:-1;
}
img.logo{
    height:71px
}

.nav{
    display: flex;
    align-items: center;
    gap: 30px;
    background: transparent;
    padding: 10px 18px;
}
.logo{
    height:42px;
}
.menu{
    display:flex;
    list-style:none;
    padding:0;
    margin:0;
    gap: 8px;
}
.menu > li{
    position: relative;
    float:none;
}
.menu > li > a{
    color:#fff;
    text-decoration:none;
    font-size:14px; 
    font-weight: bold;
    padding: 28px 29px;
    display:block;
}
.menu > li > a:hover{
    background-color:#ffb020;
}
/* 子菜单sup：默认隐藏！重点 */
.sup{
    position:absolute;
    top:100%;
    left:0;
    list-style:none;
    padding:0;
    margin:0;
    background:#222;
    display:none;
    width: 114px;
}
.sup li a{
    color:#fff;
    text-decoration:none;
    font-size:17px;
    font-weight:100 ;
    padding:10px 21px;
    display:block;
}
.sup li a:hover{
    background:#444;
}
/* 鼠标悬浮才显示下拉，这句不能少！ */
.drop:hover .sup{
    display:block;
}