@media screen and (max-width: 640px)  {
    #header_top .container{justify-content: space-between;}
    #logo{display:none;}
    #logo_small{height:70%;}
    #nav{width:100%;display:flex;}
    .container{width:95%;}
}
@media screen and (min-width: 640px)  {
    .container{width:90%;}
    #logo_small{display:none;}
    #header_top .container{justify-content: flex-end;}   
    #header_bottom{margin:1em auto}
    #nav{width:calc(100% - 420px);}

}
@media screen and (min-width: 960px) {
}
@media screen and (min-width:1200px){
    .container{width:1200px;}
}
body{
    margin:0;
    padding:0;   
    width:100%; 
    display: flex;
    flex-direction: column;
    align-content: center;
    font-family: "Microsoft YaHei", SimHei, sans-serif;
    font-size: 14px;
}
a{
    text-decoration: none;
    color:black;

}
.container{
    align-self: center;
    margin-left: auto;
    margin-right:auto;
}
#header{
    display: flex;
    flex-direction: column;
    width:100%; 
}
#header_top{
    width:100%;
    height: 3em;
    background-color:  #6a1c93;
}
#header_top .container{
    height:100%;
    display:flex;
    flex-direction: row;
    color:white;
    align-items: center;
}
#header_top .container a{
    color:white;
}
#header_top .container span{
    margin:0 2em;
}
#header_bottom{
    display:flex;
    flex-direction: row;
    justify-content: space-between;

}

#nav{
    font-size:16px;
    font-weight: bold;
    color:#000000;
}
#nav ul{
    width:100%;
    height:100%;
    margin: 0;
    padding:0;
    display:flex;
    flex-direction: row;
    align-items: center;
    justify-content: space-around;
}
#nav li{
    margin:0;
    padding:0;
    list-style-type: none;
}
#footer{
    width:100%;
    height:3em;    
    background-color: #6a1c93;
}
#footer .container{
    height:100%;
    color:white;
    display:flex;
    flex-direction: row;
    align-items:center;
    justify-content: center;
    text-align:center;
}