Superb Adaptation; Level Editor Please :)
This was definitely a great adaptation of Portal into 2D. The guys who made portal said that they made a 2D model of it first - I wonder if it was like this? The only thing I wished you had was it's sense of humor. Of course not everyone is a comdian, but it would have been nice, as humor is one of the great things about Portal (only thing keeping you from a 10).
I was actually thinking about making a 2D version of the game back when I saw the commercials, and I would still love to make an isometric one. Platforming's never been my thing though :(.
I don't know if you could flesh this out a bit more, but I had an idea where you could get the whole "half in on one side, half out on the other" by duplicating the movie clip to the other side, while moving a transparent mask to cover parts, then repositioning the original movie clip and deleting the duplicated one when more than half of you passes through. This is only an idea though - I plan on testing it soon , but seeing as you already have a basic engine of sorts for it, maybe you could try it out and tell me if it works.