This game is one of those games that you look at and you're like "meh" and then you play it and you're like "man, this is fun". I actually think there's a lot of potential here. I do have some suggestions:

1) The arrow is meaningless and in the way. All it does is tell you what you already know, and actually it does a bad job of that because it's actually pointing in the OPPOSITE direction that gravity is being applied to you. If you were going to keep the arrow, I would say that you should have it tell you what the NEXT gravity shift will be. Also, invert it so that it's pointing in the direction that GRAVITY WILL BE DRAGGING YOU IN!!

2) The player and the coin stay in the same place, but the map rotates, and the player's gravity direction rotates. I find this combination very disorienting. This one is more of an idea and not necessarily "the right way to do it" but here's how I would do it: The gravity should rotate, and the players' controls should shift, but everyone else should stay where it is, including the map. You could add "wall jumping" as a way to allow for vertical movement when the gravity shifts right or left. Again, this is JUST A SUGGESTION, not necessarily what I think would be "correct".

3) Decide if you want black borders for your sprites or not, and make that the standard. Obviously your platforms need some polish, but the coin as well as the platforms, in my estimation, would look better if they had a black border around them. When I do pixel art, either everything has a black outline or nothing does, and I find that really helps to make the game look cohesive.

All this said, I know this was probably a harsh review, but I actually think that if you added some levels and a little more depth to the gameplay (WALL JUMPING), that this could be a very fun game. Good luck.