.loader {
    width: 42px;
    height: 42px;
    border: 4px solid black;
    border-bottom-color: transparent;
    border-radius: 50%;
    display: inline-block;
    box-sizing: border-box;
    animation: rotation 1.3s linear infinite;
}

.loader {
    position: absolute;
    left: calc(50% - 21px);
    top: calc(50% - 21px);
}

@keyframes rotation {
    0% {
        transform: rotate(0deg);
    }

    100% {
        transform: rotate(360deg);
    }
}