nav {width:200px;text-align:center}
menu,main {position:fixed;top:4px}
menu {padding:0;left:calc(50% - 546px);margin:0;width:190px;border-radius:11px 0 0 0}
menu * {margin:1px 0}
menu a {color:#000}
menu a:hover {color:#fff;background-color:#000}
main {right:calc(50% - 547px);width:900px;border-radius:0 11px 11px 0}