For the most part, it improves and expands really well what made the first game so good. They could have used the new objects a little more, though. Some of the later puzzles, even though are very elegant, basically rely mostly on the lasers.

My only major criticism would be the story. First, the narrative takes a more traditional/generic approach where everything is exposed to you through dialog with other characters. I think the first left a little more to interpretation and reflection. With regard to the story, I felt the overall arc very corny. The themes addressed in the first one were much more thought-provoking than what's presented here.