#overlay {
    position: fixed;
    width: 100%;
    height: 100%;
    display: none;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: rgba(0,0,0,.2);
    z-index: 100000;
}

#loader {
    -webkit-animation: spin 1s linear infinite;
    animation: spin 1s linear infinite;
    border: 3px solid #ddd;
    border-top: 3px solid #42a5f5;
    border-radius: 50%;
    height: 75px;
    width: 75px;
    position: absolute;
    top: 50%;
    left: 50%;
    margin-top: -25px;
    margin-left: -25px;
}

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

    100% {
        transform: rotate(360deg);
    }
}