style.css

body{
    margin: 0;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: #000;
    overflow: hidden;
}
.container{
    font-size: 10px;
    width: 40em;
    height: 40em;
    position: relative;
}
.sun{
    position: absolute;
    top: 12.5em;
    left: 12.5em;
    width: 15em;
    height: 15em;
    background-color: #ffcc00;
    border-radius: 50%;
    box-shadow: 0 0 3em white;
}
.earth, 
.moon{
    position: absolute;
    border-style: solid;
    border-color: white transparent transparent transparent;

    border-width:  0.1em 0.1em 0 0;
    border-radius: 50%;
}
.earth{
    top: 5em;
    left: 5em;
    width:30em;
    height: 30em;
    animation:orbit 36.5s linear infinite;
}
.moon{
    top: 0;
    right: 0;
    height: 8em;
    width: 8em;
    animation: orbit 2.7s linear infinite;

}
.earth::before ,.moon::before{
    content: '';
    position: absolute;
    border-radius: 50%;
}
.earth::before{
    top: 2.8em;
    right: 2.8em;
    width: 3em;
    height: 3em;
    background-color: #72cdfa;
}
.moon::before{
    top: 0.8em;
    right:0.2em;
    width:1.2em;
    height:1.2em;
    background-color:#ccc;
}
@keyframes orbit{
    to{
        transform: rotate(360deg);
    }
}