@keyframes loader-animation {
    0% {
        width: 0%;
    }

    49% {
        width: 100%;
        left: 0%
    }

    50% {
        left: 100%;
    }

    100% {
        left: 0%;
        width: 100%
    }
}

.loader {
    height: 5px;
    width: 100%;
    position: fixed;
    background: rgba(0,0,0,0.5);
    height: 100%;
    width: 100%;
    top: 0;
    left: 0px;
    text-align: center;
    /*padding-top: 20%;*/
    z-index: 9999;
}

    .loader .bar {
        position: relative;
        height: 5px;
        background-color: red;
        animation-name: loader-animation;
        animation-duration: 3s;
        animation-iteration-count: infinite;
        animation-timing-function: ease-in-out;
    }