How do you feel about the brief puzzle mechanics?
So, while they were present and understandable, they could use some polish, which is expected from this stage of our game development. Level-design-wise I would add something very basic to introduce the player to the mechanics. Something along the lines of an arrow pointing to the green areas, or a pop-up on the green areas telling the player to do something.
Were you able to figure them out relatively quickly with a bit of trial and error?
Yes, through a bit of trial and error. A specific thing that got me was the pit area near the end. I had thought that lead to certain death, until I accidentally fell in and found the green area to unlock the path. That could be solved by either a larger camera or something that hints there's something down there.
Did you get an understanding of the physics of the current body parts that were present?
Yes. The physics were a bit awkward to get used to. At one point I stacked the parts and was able to use them as a step-stool to try and "parkour" my way over a wall. It didn't succeed but maybe it's a possibility you may want to think about.