Z Chamber 13 Developer Commentary
This was chamber 10 (and chamber 12 in the code) in PortalZ: The 2020 Slice.
Developer commentary may include spoilers; I recommend you finish PortalZ before reading further.
As I have said before, I really liked the concept of Portal test chambers being made out of movable panels, and I really disliked waiting for lifts. Having the floor turn into staircases addressed both of those.
Originally, this chamber had a much different layout, with a sideways button granting you access to a sideways fling over goo on the other side of the chamber. That had the issue of making you replay the entire chamber from the start if you accidentally dropped the cube into the goo during that final fling. This redesigned version makes raising the sideways button sort of a checkpoint, and also lets you reuse an element for multiple parts of the test. I am incredibly happy with it.