I did some terraforming that went a bit odd.
It was a volcanic planet with extreme tectonic, extreme heat, and toxic atmosphere. With atmosphere removal now available, I wanted to turn it into a plain atmosphere-less barren planet for industry. (Because it had double ultrarich ores.) I removed tectonic first, then heat, then toxic atmosphere. Then I intended to remove any remaining atmosphere.
What I expected to happen, with each modification:
Volcanic -> Volcanic -> Toxic -> Barren-desert -> Barren
Instead what happened:
Volcanic -> Volcanic -> Barren (but with toxic atmosphere) -> Desert (habitable) -> Can't proceed because removing atmosphere from habitable planets is not allowed.
It's odd to me for three reasons:
* I believe that barren planets have no atmosphere by definition, as generated. That's why I expected it to be a toxic planet. But it ended up barren with a toxic atmosphere, which doesn't really make sense considering the description and appearance of barren planets.
* The description for atmospheric filters says that it converts toxins into inert, non-breathable gasses. But completing it created a breathable atmosphere. I felt like I skipped a step there somehow. Maybe it makes sense if we just assume there was oxygen around already, but it did trap me into habitability.
* I believe my plan would have worked if I had done the steps in a different order, possibly removing the atmosphere before removing the heat making it go directly from volcanic to atmosphere-less barren. Feels like an unpleasant gotcha that it depends on order.
I'm not suggesting any particular changes, but I'm sharing the experience, because it doesn't seem like it worked as intended.
(Also, probably a bug: Integration Corps gives the growth bonus before it's done building.)