.loader {
    width: 32px;
    height: 32px;
    position: relative;
    border-radius: 50%;
    color: #91CF4F;
    animation: fill 1s ease-in infinite alternate;
}
.loader::before , .loader::after {
    content: '';
    position: absolute;
    height: 100%;
    width: 100%;
    border-radius: 50%;
    left: 48px;
    top: 0;
    animation: fill 0.9s ease-in infinite alternate;
}

.loader::after {
    left: auto;
    right: 48px;
    animation-duration: 1.1s;
}

@keyframes fill {
    0% {  box-shadow: 0 0 0 2px inset }
    100%{ box-shadow: 0 0 0 10px inset }
}