@media all and (max-width: 1200px) {

     nav{
          position:fixed;
          height: 100%;
          background: white;
          width: 180px;
          border-right: 2px solid whitesmoke;
          box-sizing: border-box;
     }

     #content{
          width: calc(100% - 180px);
          margin-left: 180px;
     }

     #content section{
          width: 600px;
          margin-left: 44px;
     }
}