:root{--ink:#16161a;--muted:#5b5b66;--line:#d8d8e0;--accent:#1d4ed8;--danger:#b42318;--warn-bg:#fef3c7;--warn-ink:#7c2d12;color-scheme:light}*{box-sizing:border-box}body{margin:0;font-family:ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,sans-serif;color:var(--ink);background:#f7f7fb;line-height:1.5}.sandbox-banner{position:-webkit-sticky;position:sticky;top:0;z-index:100;padding:.5rem 1rem;background:var(--warn-bg);color:var(--warn-ink);font-weight:700;letter-spacing:.04em;text-align:center;border-bottom:2px solid var(--warn-ink)}header.masthead{display:flex;gap:1.5rem;align-items:baseline;padding:1rem 1.5rem;border-bottom:1px solid var(--line);background:#fff}header.masthead a{color:var(--accent);text-decoration:none}main{max-width:56rem;margin:0 auto;padding:1.5rem}.card{background:#fff;border:1px solid var(--line);border-radius:.5rem;padding:1.25rem;margin-bottom:1.25rem}label{display:block;margin:.75rem 0 .25rem;font-weight:600;font-size:.9rem}input,select{width:100%;padding:.5rem;border:1px solid var(--line);border-radius:.25rem;font:inherit}button{padding:.55rem 1rem;border:1px solid var(--accent);border-radius:.25rem;background:var(--accent);color:#fff;font:inherit;font-weight:600;cursor:pointer}button.secondary{background:#fff;color:var(--accent)}button:disabled{opacity:.5;cursor:not-allowed}.problem{margin-top:1rem;padding:.75rem;border:1px solid var(--danger);border-radius:.25rem;color:var(--danger);background:#fff5f5}.code{font-family:ui-monospace,SFMono-Regular,Menlo,monospace;font-size:1.35rem;letter-spacing:.08em}.grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));grid-gap:0 1rem;gap:0 1rem}.muted{color:var(--muted);font-size:.9rem}