style.css

*{
    box-sizing: border-box;
}
:root{
    font-family: sans-serif;
    line-height: 1.6;
    font-size: 16px;
    color: white;
}
header{
    padding:10px;
    position:static;
    top:0;
    margin-top: 0;
    z-index:10;
}
.header-ul{
    list-style:none;
    margin:0;
    padding-left:0;
    display:flex;
    flex-wrap:wrap
}
.header-ul>li:first-child{
    margin-left: auto;
}
.header-ul>li:not(:last-child){
    margin-right: 5px;
}
.header-ul a{
    display: block;
    padding: 10px;
    color: white;
    text-decoration: none;
}
.header-ul a:hover{
    padding-bottom: 8px;
    border-bottom: 2px dotted white;
}
body{
    display: flex;
    flex-direction: column;
    margin:0;
    min-height:100vh;
    background:url(background.webp) center/cover no-repeat fixed
}
main{
    padding-top: 20px;
    position: relative;
    flex-grow: 1;
}