Gravity field

Gravity Walls are walls with arrows painted on them that can control gravity, causing Mario to be attracted by such force according to the direction the arrows are pointing in. Gravity Walls appear in Super Mario Galaxy, in a few galaxies, such as Bowser's Dark Matter Plant. The direction of some walls can be changed (and therefore, the gravity) by a Gravity Arrow.

Blue Walls
A Blue Wall makes the force of gravity pull Mario downward.

Purple Wall
A Purple Wall makes the force of gravity pull Mario upward.

Green Wall
A Green Wall makes the force of gravity pull Mario from the right.

Gray Wall
A Gray Wall makes the force of gravity pull Mario from the left.