Making the way through the 3D level and the 2D level is a really great idea. I liked the buttons in the 2D part that helped the progression of the 3D. I think you hit the theme of the challenge really well and it was a lot of fun. Well done!
I would have liked to see maybe some things in the 3D level help out the 2D level as well, but that's not going to affect my rating, I think you did really well with what you already have. I would like to see this concept taken further.