body{font-family:sans-serif;background:#0f172a;display:flex;justify-content:center;align-items:center;height:100vh;margin:0}
.card{background:#fff;padding:2rem;border-radius:12px;width:300px;text-align:center}
input,button{width:100%;padding:.6rem;margin:.4rem 0;box-sizing:border-box}
button{background:#2563eb;color:#fff;border:0;border-radius:6px;cursor:pointer}
.err{color:#dc2626}