style.css

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: cursive;
}

body{
    background: #222;
    overflow: hidden;
}

.circle{
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 1400px;
    height: 1400px;
    border-radius: 50%;
}

.circle span{
    position: absolute;
    display: block;
    border-radius: 50%;
    overflow: hidden;
    background: #222;
    animation: animate 5s cubic-bezier(.64, -.56, .36, 1.56) infinite;
}

@keyframes animate{
    0%{
        transform: rotate(0deg);
    }
    80%, 100%{
        transform: rotate(360deg);
    }
}

.circle span:nth-child(1){
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    animation-delay: 0;
}
.circle span:nth-child(2){
    top: 150px;
    left: 150px;
    right: 150px;
    bottom: 150px;
    animation-delay: 0.2s;
}
.circle span:nth-child(3){
    top: 300px;
    left: 300px;
    right: 300px;
    bottom: 300px;
    animation-delay: 0.4s;
}
.circle span:nth-child(4){
    top: 450px;
    left: 450px;
    right: 450px;
    bottom: 450px;
    animation-delay: 0.6s;
}
.circle span:nth-child(5){
    top: 600px;
    left: 600px;
    right: 600px;
    bottom: 600px;
    animation-delay: 0.8s;
}

.circle span::before{
    content: attr(data-text);
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 10em;
    text-align: center;
    font-weight: 900;
    color: #fff;
    text-transform: uppercase;
}

.circle span::after{
    content: '';
    position: absolute;
    top:0;
    left:0;
    width: 100%;
    height: 100%;
    border-radius: 50%;
    box-shadow: inset 0 0 50px rgba(0, 0, 0, .5),
                inset 0 0 75px rgba(0, 0, 0, .5),
                inset 0 0 100px rgba(0, 0, 0, .5),
                inset 0 0 125px rgba(0, 0, 0, .5);
}