Just a quick review - I like the melodies, tones, and general composition.
Drums need to come up in the mix by a db. Not just the kick. The snare is somewhat
lacking though - could be replaced with a more accurate snare sound. The kick could use some top end eq'd into it.
As per the drum part changes at - I like the first change(1:29 and 3:29) but the second change (1:44 and 3:44) along with the effect you added seemed a little obnoxious. That's just personal opinion though.