Pretty simple and intuitive; you did a great job of leaving the correct amount of space for me to figure out what to do, which was awesome. That did come with a bit of confusion at certain things just appearing and disappearing, though, which doesn't come with the same intuitiveness of "if I don't move at all, nothing happens... so I guess I should push this button.. oh! It made a bridge," which is the feeling you get in the earlier stages.
The game was short enough that it wasn't too frustrating at all to quickly hop back in for another go at finding another ending, which was fun for a game of this scope (although, again, the lack of extra visual feedback made it difficult to discern precisely what I had managed to do differently, so, like with my earlier comment, either some more feedback or, if necessary, even a written hint might serve well here).
The lack of visual feedback also made it difficult to see the connection between the levels sometimes, too...
It might sound like I'm going hard on that point, but it's just because everything else was quite tight and thus only exemplified where the more obvious feedback was lacking.
Interesting and well-executed game, despite that. : )