A skill based maze game hmm..
This is more of a skill based game rather than a maze game. It reminds me of 'When Pigs Fly' which was also a maneuvering kind of game with gravitational effects.
First the things I like - the fact that it actually takes skill to move through the maze. The implementation of gravity as a force to interact with. It's a sound concept.
The rest needs to be enhanced a whole lot more. I think the controls are too sluggish and even the gravity pull is too weak. You need to test and strike a good solid balance between path thickness, movement sensitivity, gravity strength, and deceleration. As of now I think the movement is way too slow, the gravity is almost ineffective and there's way too much momentum in the movement which allows for very slow change of direction for the size of the path now.
Play around with those variables and come up with a good balance that allows for swift but challenging play.
Next up is level design. As of now you've got the 1 idea and while it's sound, you can start to add more things to a level instead of just movement. I was actually pretty excited when I got to the water in the first stage because you could have used that as a means of flotation which would've flipped the gravity the other way round for that particular section. You could include magnets in the path to contend with (assuming the rat-ball is magnetic) or fans that blow the ball of course and other forces to contend with instead of just gravity.
I would suggest a major revamp of the art - for one thing the colour scheme you chose is terrible on the eyes. Staring at that brown/grey combination doesn't feel comfortable at all. I would've liked to see more texture if possible considering you thought up some context - the mouse and wizard what not - so you could've gone with some texture instead of solid colours, but even then the colours need to be chosen properly so that they're comfy on the eyes, especially because there's going to be a lot of staring at the same thing in a game like this.
Lots of room for improvements here, which is a good start.