Z Chamber 11 Developer Commentary

Developer commentary may include spoilers; I recommend you finish PortalZ before reading further.

The first room has cubes, a sphere, and a radio about the floor, 4 buttons on the ceiling corners, and a big glowing down arrow in the middle, connected to a pedestal button.
This first room makes it impossible to miss the point: there are gravity fields that turn on and off.  There are other ways this could have been introduced, bUt I liked the idea of a big room full of things that rise to the ceiling at your command.  The pillar is also big enough that, while you can still see the exit door indicators, attention is still squarely on the gravity field indicator.

A gravity field holds a cube onto a ceiling button.
This room introduces uses of gravity fields that will become more important in chamber twelve—specifically, using them to perform wall-to-floor jumps and buttons that create their own fields to hold cubes to them.  The chamber layout even makes the player walk past the latter a second time to get to the exit.

The floor button in the third room connects to a pedestal button that connects to a cube dropper.
The floor button could have activated the box dropper directly, but it was not obvious to all players that that was the case.  Having it activate a pedestal button that the player had to press made that connection more apparent.