.loader {
    width: 16px;
    height: 16px;
    border-radius: 50%;
    display: block;
    margin: 15px auto;
    position: relative;
    background: #FFF;
    box-shadow: -24px 0 #FFF, 24px 0 #FFF;
    box-sizing: border-box;
    animation: shadowPulse 2s linear infinite;
}

@keyframes shadowPulse {
    33% {
        background: #FFF;
        box-shadow: -24px 0 #FF3D00, 24px 0 #FFF;
    }

    66% {
        background: #FF3D00;
        box-shadow: -24px 0 #FFF, 24px 0 #FFF;
    }

    100% {
        background: #FFF;
        box-shadow: -24px 0 #FFF, 24px 0 #FF3D00;
    }
}