I concur with the preceding reviewers.
I would agree with what some other people have said that this song is a bit disjointed. I think the trick is the changes in mood that you describe--the chaotic part is practically atonal, with an extremely heavy beat, whereas, the twilighty part has a clearly defined melody and is occasionally without drums. I do normally like songs with mood changes and similar shifting, but the ones in this song are so extreme that they're disruptive to my listening. (Just as I appreciate eating cake but not giant blocks of sugar, if you'll pardon a bizarre metaphor.) 1:41, 2:59, and 2:23 are particularly disorienting transitions and could be improved significantly.
I would, however, also agree that the individual parts are pretty good, and at the same time I really appreciate the part at the end (from 3:12 on) when the two are fused together: that's probably my favorite part of the song. In general, if you made the two separate parts more similar to each other, and/or made the segues between them more gradual (although the sudden, sharp changes _within_ the chaotic part were quite cool.) the piece would be improved.