html,body{
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    position: fixed;
}
body>img{
    width:200%;
    height: 200%;
}
.intro{
    position:absolute;
    top:20px;
    left:20px;
    bottom:20px;
    color:white;
    background: rgba(0,0,0,0.3);
    border-radius: 10px;
    padding: 10px 20px;
}
.intro .no-scroll-list
{
    height: calc(100% - 60px);
    border: 1px solid silver;
    overflow: hidden;
    border-radius: 5px;
    background: rgba(0,0,0,0.3);
}
.intro .no-scroll-list li{
    cursor: pointer;
    padding: 5px 10px;
}
.intro .no-scroll-list li:hover{
    background: rgba(233,233,233,0.5);
}
.usage{

}