Ominous! I think if the world got darker and more twisted as you gathered materials it would really tie together the idea that the tower was an evil entity. Maybe the player initially didn't think much about what they were doing, not enough to resist the tower's commands, but as the world around changes for the worst, that is when they realizes they have to make that final choice.
Some critiques: I didn't like the pixelation effect that much, I think it is too harsh. In moderation, it can make a 3D game like this look very charming, but in this case it made it very difficult to see distant things, especially the tower, which is the main thing I wanted to see in detail. The gathering is also repetitive. Perhaps if each time a new material was requested, or, again, the world visibly changed, that wouldn't be the case.
Overall though, you did a great job, congrats!