:root{color-scheme:light dark}body{margin:0;font-family:system-ui,sans-serif;background:#f6f7f9;color:#18202c;display:grid;min-height:100vh;place-items:center}@media(prefers-color-scheme:dark){body{background:#0f141c;color:#eef2f7}}.caja{max-width:420px;padding:28px 24px;margin:16px}h1{font-size:20px;margin:0 0 12px}p{line-height:1.5;color:inherit}a.btn{display:inline-block;margin-top:12px;padding:11px 18px;border-radius:9px;background:#e05d34;color:#fff;text-decoration:none;font-weight:600}