They're many strengths of this Design in my opinion, firstly the vectors and minimalism! There is also some gradients used to create depth in the final image. Such as the background fading out from light to dark blue, to show how deep the sea actually is! Simple but a really clever idea to create depth in a vector image. There isn't many negatives, but if I had to be picky I would add more detail to the main objects in the game like the boat and fish etc.