css特效动画——转圈的加载动画

<div class="loading"></div>

.loading {
    width: 40px; height: 40px;
    margin: auto;
    position: relative;
}
.loading::before {
    content: "";
    width: 4px; height: 4px;
    border-radius: 100%;
    color: rgba(0, 0, 0, .4);
    box-shadow: 0 -10px rgba(0,0,0,.9),    /* top */
        10px 0px,                  /* right */
        0 10px,                    /* bottom */
        -10px 0 rgba(0,0,0,.7),    /* left */

        -7px -7px rgba(0,0,0,.8),  /* left-top */
        7px -7px rgba(0,0,0,1),    /* right-top */
        7px 7px,                   /* right-bottom */
        -7px 7px;                  /* left-bottom */
    animation: spin 1s steps(8) infinite;
    /* center */
    position: absolute;
    top: 0; right: 0; bottom: 0; left: 0;
    margin: auto;
}
@keyframes {
     0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}