.loader {
    position: fixed;
    top: 50%;
    left: 38%;
    right: 62%;
    z-index: 1;
    margin: -50px 0 0 -75px;
    border: 16px solid #f3f3f3; /* Light grey */
    border-top: 16px solid #191939; /* Blue */
    border-radius: 50%;
    width: 75px;
    height: 75px;
    animation: spin 2s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}