*,*:before,*:after{box-sizing:border-box}html,body{margin:0;padding:0;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif;line-height:1.5;color:#111;background:#fff}main{max-width:640px;margin:0 auto;padding:4rem 1.5rem}h1{font-size:2.5rem;margin:0 0 .5rem}p{font-size:1.125rem;margin:0 0 2rem;color:#444}nav{display:flex;gap:1.5rem}nav a{color:#06c;text-decoration:none;font-weight:500}nav a:hover{text-decoration:underline}