body {font-family: Arial, sans-serif; background:#f5f5f5; display:flex; align-items:center; justify-content:center; height:100vh;}
        .login-box {background:#fff; padding:2rem; border-radius:8px; box-shadow:0 2px 8px rgba(0,0,0,.1); width:320px;}
        .login-box h2 {margin-top:0; text-align:center;}
        .field {margin-bottom:1rem;}
        .field label {display:block; margin-bottom:.3rem;}
        .field input {width:100%; padding:.5rem; border:1px solid #ccc; border-radius:4px;}
        .error {color:#d00; font-size:.9rem; margin-top:.3rem;}
        .btn {width:100%; padding:.7rem; background:#0069d9; color:#fff; border:none; border-radius:4px; cursor:pointer;}
        .btn:disabled {background:#aaa; cursor: not-allowed;}
        .message {margin-top:1rem; text-align:center;}