*{box-sizing:border-box}body,html{margin:0;padding:0;font-family:system-ui,sans-serif;line-height:1.5}main{max-width:40rem;margin:0 auto;padding:2rem 1rem}nav{display:flex;gap:1rem;padding:1rem;border-bottom:1px solid #e5e5e5}nav a{color:#2563eb;text-decoration:none}nav a:hover{text-decoration:underline}