JavaScript/Animation/reverse

 var planet = document.getElementById('earth'),
		Animation = planet.animate([{
	 transform: 'rotate(0deg)',
	 fill : 'blue'
 }, {
	 transform: 'rotate(360deg)',
	 fill : 'skyblue' 
 }
 ], {
 duration: 2000,
 iterations: Infinity,
 fill: 'forwards'
 });
 	
 // activate control buttons	
 document.querySelector('#back').addEventListener('click', runBackwards);
 document.querySelector('#play').addEventListener('click', togglePlayPause);
 document.querySelector('#forward').addEventListener('click', runForwards); 
 function runBackwards () {
	Animation.reverse();
 } 
 function runForwards () {
 Animation.playbackRate = 3;			
 } 
 
 function togglePlayPause () {
	if (document.querySelector('#play').textContent == '❙❙') {
		document.querySelector('#play').textContent = '►';
		Animation.pause();
	} else {
		document.querySelector('#play').textContent = '❙❙';
		Animation.play();		
		Animation.playbackRate = 1;				
	}
 }