:root{--ink:#0b132b;--muted:#475569;--accent:#1e40af;--bg:#f8fafc;--border:#e2e8f0}*{box-sizing:border-box}body{background:var(--bg);color:var(--ink);margin:0;font-family:system-ui,-apple-system,Segoe UI,sans-serif;line-height:1.5}main{max-width:640px;margin:15vh auto 0;padding:0 16px}h1{margin:0 0 .5rem;font-size:1.75rem}p{color:var(--muted)}button{font:inherit;border:1px solid var(--accent);background:var(--accent);color:#fff;cursor:pointer;border-radius:6px;padding:.6rem 1.1rem}button.secondary{color:var(--accent);background:0 0}.error{border:1px solid var(--border);background:#fff;border-left:3px solid #b91c1c;padding:.75rem 1rem}