.center{
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    -ms-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
}

.centered {
   position: fixed;
   top: 50%;
   left: 50%;
   transform: translate(-50%, -50%);
}
.loader {
   width: 500px;
   height: 500px;
}
body {
   background-color: purple;
}