I just wanted to point out one thing that is potentially dangerous when it comes to gameplay: when sister is changing gravity she falls back if no ground is to be found but while falling she can move in the air. This shouldn't happen because the player can just change gravity, wait until sister starts to fall & move to, in normal conditions, unreachable parts of the level. I think we should make the entire gravity switching process to be fixed, with no possibility to move while ascending or descending from the air.