The idea is nice, but I would have liked for the gravity to be unable to "switch" to the direction that is already active, and to have the player controls adapt to the direction (Up and Down arrows when the player is on the wall, for example), and the levels might need some more design to prevent the player from just waiting for the easiest direction to progress.
Other than that and a few collision issues, the game plays fine and it was an enjoyable experience, nice work!