body{
    background: url("./pexels-alyona-boytsova-10426128.jpg") no-repeat;
    background-size: cover;
    font-family: Arial;
    color: white;

}
ul{
    margin: 0px;
    padding: 0px;
    list-style: none;
}
ul li{
    float: left;
    width: 200px;
    height: 40px;
    background-color: black
    ;
    opacity: .8;
    line-height: 40px;
   text-align: center;
   font-size: 20px; 
   margin-right: 2px;
   
}
ul li a {
    text-decoration: none;
    color: white;
    display: block;
}
ul li a:hover{
    background-color: green;
}
ul li ul li{
    display:none;

}
ul li:hover ul li{
    display:block;
}