Rotating Multiple Objects at once (OnCollision)

Im working on a game similar to Run when my character can move left and right and if it touches the walls it "Rotates Gravity". Anyone got any ideas on what I can do?

In "Edit > Project Settings > Physics" you can set which direction gravity is pulling in (X,Y,Z) so you could just change this value in code... I haven't played Run but from what you describe, this should be easy enough.

Hope it helps (this is my first attempt at helping anyone ;) )