header{background:#fff;border-right:1px solid #000;width:400px;padding:40px;display:block;position:fixed;top:0;bottom:0;left:0}header nav{flex-direction:column;display:flex}header nav a{color:#000;border-radius:10px;align-items:center;gap:10px;padding:20px;font-weight:900;text-decoration:none;display:flex}header nav a svg{stroke:#000}header nav a.navactive{color:#fff;background:#000}header nav a.navactive svg{stroke:#fff}body{margin-left:400px}