style.css

html, body {
    /* The universe takes up all available space */
    width: 100%;
    height: 100%;
    
    /* The universe is black */
    background-color: black;
}

#sun {
    position: absolute;
    /* Positions the top-left corner of the image to be *
    /* in the middle of the box */
    top: 50%;
    left: 50%;
    
    /* Play with these numbers to see what it does */
    height: 200px;
    width: 200px;
    margin-top: -100px; 
    margin-left: -100px;
    
    border-color: orange;
    border-width: 8px;
    border-style: solid;
    border-radius: 50%;
    
    box-shadow: 0 0 128px red;
}

#earth {
    position: absolute;
    top: 0%;
    left: 50%;
    
    height: 50px;
    width: 50px;
    margin-left: -25px;
    margin-top: -25px;
}

#earth-orbit {
    position: absolute;
    top: 50%;
    left: 50%;
    
    width: 500px;
    height: 500px;
    margin-top: -250px;
    margin-left: -250px;
    
    border-width: 2px;
    border-style: dotted;
    border-color: gray;
    border-radius: 50%;
    
    -webkit-animation: spin-right 18s linear infinite;
    animation: spin-right 18s linear infinite;
}

#moon {
	position: absolute;
	top: 0%;
	left: 50%;
	
	height: 10px;
	width: 10px;
	margin-left: -5px;
	margin-top: -5px;
}

#moon-orbit {
    position: absolute;
    top: 0%;
    left: 50%;
    
    height: 100px;
    width: 100px;
    margin-left: -50px;
    margin-top: -50px;
    
    border-width: 2px;
    border-style: dotted;
    border-color: gray;
    border-radius: 50%;
       
    -webkit-animation: spin-right 7s linear infinite;
    animation: spin-right 7s linear infinite
}


@-webkit-keyframes spin-right {
  100% {
      -webkit-transform: rotate(360deg);
  }
}

@keyframes spin-right {
    100% {
        transform: rotate(360deg);
    }
}