*{box-sizing:border-box;margin:0;padding:0}body{font-family:system-ui,-apple-system,sans-serif;background:#f5f5f5;color:#333}.container{max-width:600px;margin:80px auto;text-align:center}h1{font-size:2.5rem;margin-bottom:2rem;color:#1a1a1a}.card{background:#fff;border-radius:12px;padding:2rem;box-shadow:0 2px 8px #0000001a}button{background:#4f46e5;color:#fff;border:none;padding:.75rem 2rem;border-radius:8px;font-size:1rem;cursor:pointer;transition:background .2s}button:hover:not(:disabled){background:#4338ca}button:disabled{opacity:.6;cursor:not-allowed}.result{margin-top:1.5rem;text-align:left;line-height:2}.error{margin-top:1rem;color:#dc2626;font-weight:500}