.spinner {
    width: 40px;
    height: 40px;
    border: 4px solid #dcdcdc;
    border-top: 4px solid #000;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    from { transform: rotate(0deg); }
    to   { transform: rotate(360deg); }
}
.spinner {
    width: 50px;
    height: 50px;
    border: 5px solid #ddd;
    border-top: 5px solid #333;
    border-radius: 50%;
    animation: spin .8s linear infinite;
    margin: 10px auto;
}