My solution for the Redux puzzle

My solution for the Redux puzzle by chris@redux:

http://redux.com/stream/item/792903/Which-figure-does-not-belong

Blame the bad drawing on my limited Gimp skills.

Image1Image2

 

With the center figure, you have always one attribute changing from and to this one, while the other ones always have 2 attributes changing.

If you remove the center figure, everything is symmetric.