.loader-walk {
    width: 100px;
    height: 40px;
    position: absolute;
    top: 50%;
    left: 50%;
    -webkit-transform: translate(-50%, -50%);
    transform: translate(-50%, -50%);
}

    .loader-walk > div {
        content: "";
        width: 20px;
        height: 20px;
        background: #2196F3;
        border-radius: 100%;
        position: absolute;
        -webkit-animation: animate 2s linear infinite;
        animation: animate 2s linear infinite;
    }

        .loader-walk > div:nth-of-type(1) {
            -webkit-animation-delay: -.4s;
            animation-delay: -.4s;
        }

        .loader-walk > div:nth-of-type(2) {
            -webkit-animation-delay: -.8s;
            animation-delay: -.8s;
        }

        .loader-walk > div:nth-of-type(3) {
            -webkit-animation-delay: -1.2s;
            animation-delay: -1.2s;
        }

        .loader-walk > div:nth-of-type(4) {
            -webkit-animation-delay: -1.6s;
            animation-delay: -1.6s;
        }

@-webkit-keyframes animate {
    0% {
        left: 100px;
        top: 0;
    }

    80% {
        left: 0;
        top: 0;
    }

    85% {
        left: 0;
        top: -20px;
        width: 20px;
        height: 20px;
    }

    90% {
        width: 40px;
        height: 15px;
    }

    95% {
        left: 100px;
        top: -20px;
        width: 20px;
        height: 20px;
    }

    100% {
        left: 100px;
        top: 0;
    }
}

@keyframes animate {
    0% {
        left: 100px;
        top: 0;
    }

    80% {
        left: 0;
        top: 0;
    }

    85% {
        left: 0;
        top: -20px;
        width: 20px;
        height: 20px;
    }

    90% {
        width: 40px;
        height: 15px;
    }

    95% {
        left: 100px;
        top: -20px;
        width: 20px;
        height: 20px;
    }

    100% {
        left: 100px;
        top: 0;
    }
}