ul {
  list-style-type: none;
 background-color:lightgray;
  top:0;
  padding: 0;
  margin:0;
  height:50%;
  width:25%;
  position:fixed;
} 
li a {
 display: block;
 color: blue;
 text-decoration: none;
 padding: 10px;
 font-family: Bangers; 
} 
li a:hover {
  background-color: green;
  color: yellow;
}  
ul:hover {
    background-color: green;
}
#main {
 margin-left: 40%;   
}
#header {
 margin-left: 40%; 
 font-family : Bangers;
}  

body {
 color: blue;
 background-image:
url(https://image.shutterstock.com/image-illustration/color-splash-series-background-design-260nw-587409425.jpg);   
}