When you've completed the game, you can start a new playthrough with developer commentary enabled. If you haven't beaten the game, be warned that some commentary may spoil puzzle solutions.

In this chamber, you'll find commentary nodes from:

[Garret Rickey] We use these moving platforms to add time pressure to puzzles. A sequence of simple decisions feels much more climactic under time pressure, in contrast to most puzzles in Portal which can be solved at the players' leisure. Puzzles that aren't time bound can be more complex, but at the expense of being less dramatic.

[Paul Graham] Sometimes little details make a huge difference. For instance, we had to add the left side to this wall to give players a visual representation of how thick it is. Without it, playtesters frequently thought the hall had just gotten impossibly narrower, panicked, and stopped making rational decisions.

[Erik Wolpaw] Before the player escapes the fire pit, the AI dialog is all delivered in a computerized monotone. After the escape, however, GLaDOS gets progressively more expressive until, by the end, she's cycling through a whole mess of emotions. The role required an actor capable of mimicking the computer-generated voice while still infusing it with some real character. And since we planned to end the game with a song, she also needed to have a good singing voice. The woman we cast, Ellen McLain, is a great mimic, a terrific actor, and a classically trained operatic soprano. So that worked out pretty good.