Summer feelings going darkness

So I had to make a painting for school. It was a expression off a picture. I had this beach look. I made the painting with wather painting and ecoline. I think the result is oke, not stunning but good enough. But I showed them to a friend of mine and he did someting wrong and so my picture off my painting was in negative. And there it was.. summer feelings going dark. I absolutly love the effect it had given the painting.