body {
    font-family: sans-serif; 
    text-align: center; 
    padding-top: 100px; 
    background: #f4f4f9;
}
.login-card {
    display: inline-block; 
    background: white; 
    padding: 30px; 
    border-radius: 8px; 
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}
.input-field {
    padding: 10px; 
    width: 200px;
}
.submit-btn {
    padding: 10px 20px; 
    background: #007bff; 
    color: white; 
    border: none; 
    border-radius: 4px; 
    cursor: pointer;
}
.spinner {
    display: none;
    width: 20px;
    height: 20px;
    border: 3px solid #f3f3f3;
    border-top: 3px solid #007bff;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 10px auto 0 auto;
}
@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}