This plays tricks on your eyes. You can see it as the butterfly moving its wings backwards, forwards, or kind of turning them both to one side. . . I don't know how to describe it. Just look at it in different ways, and you'll see what I mean. I wasn't trying to make it play tricks on your eyes, but in the end, I like how it tuned out.
It is completely my idea. If you see something pretty much like this on a different account, but plain green gradient I did make a similar version somewhere, so its fine.