body{margin:0;font-family:Arial,sans-serif;background:#f5f5f5}.container{padding:20px}header{display:flex;justify-content:space-between;align-items:center;background:#111;color:#fff;padding:15px;border-radius:8px}nav button{margin-left:10px;padding:8px 12px;border:none;background:#444;color:#fff;cursor:pointer;border-radius:4px}nav button:hover{background:#666}main{margin-top:20px;background:#fff;padding:20px;border-radius:8px}