I like the project, but it looks a lot like the regular tumbler set, to the point that the setup is mostly the same with different colored bricks and different arms holding the wheels. I suggest you try making one from scratch, and using lego bricks you can get from the buy by brick shop they have.

it's a good job, but why is there a gun? sorry i'm french i can't speak very well english... it's goob! ;)