Z Chamber 04 Developer Commentary
Developer commentary may include spoilers; I recommend you finish PortalZ before reading further.
This chamber started as “What if Portal were a platformer?” The answer is it is not very fun, so the rest of the chamber just became an introduction to the edgeless safety cube in advance of the next chamber. I actually experimented with some other mechanics, like trap or holographic platforms for this and one other level, but never got them to really feel fun, so they were all cut, and this chamber ended up a bit shorter.
There was not originally a GLaDOS line here for when you lose an edgeless safety cube—it did not even have a proper name. Thankfully, in Portal 2's co-op, GLaDOS finally refers to it by name, and I was able to splice that phrase in. While I did recreate some Portal 2 elements from scratch in other parts of the map pack—from rumors, trailers, or after it released—that clip of GLaDOS saying “edgeless safety cube” is the only thing I took directly from Portal 2.