The collision for the fox seemed to be directly linked to the sprite, 
so I tended to get caught on the sides of the platforms by my little foxy chin.

Its fun but make sure the pixels are all the same size when adding sprites. Having pixels at different sizes can make stuff look a bit wonky.

Very cool idea. Nice animation on the fox. one suggestion I have is It would be nice to add  a sound effect to indicate when the fox is changing colors. Still was a fun game tho, Good job.