The block in blue is the shape that is currently in the game (cross section). I’m wondering if it wouldn’t be out of the realm of possibility and art direction to add in the option to make the purple shape to put underneath, on ceilings while building. This might be a stretch seeing as there are already many building block options currently, but was just a thought nonetheless. Obviously this is just a suggestion for you guys, and I love the way the game looks already. As soon as I can, I’ll get a copy of this myself closer to the release date.
This suggestion is merely based off of my observation of the game through streams and not through personal experience with the game.