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:

[Chet Faliszek] We designed this hall so that players had to use a box as a shield, but many playtesters read it as an 'avoid-the-energy-ball' timing puzzle, and simply left the box behind. We solved this, in large part, by having the AI talk about the box. A lot. Once the dialog went in, playtesters went from routinely abandoning the box to never wanting it to leave their side. Since we weren't going to make players lug a box around for the rest of the game, we added a scene at the end of the level where players are forced to kill the box.

[Ellen McLain] I know that I was told that, you know, sort of the idea of Valve is that everything... Everything is planned. Everything is worked out in advance. But that's a big, fat lie. Because: The initial idea is started, and they bring an actor into the studio and they say, you know, 'Say these words for us, say this computer generated voice for us.' Okay, I'll do that. Well, then, that gives the creators other ideas. And it's... It's a rolling process; You roll from one idea into the next idea.

[Jeep Barnett] The awful end of the companion cube serves a dual purpose: it adds a lot more sinister character to our already pretty sinister AI while simultaneously training the player to use the incinerator, a key component of the final level. The training has a nice dramatic payoff, since players later get to avenge the death of their good friend the companion cube by stuffing some of the AI's important parts into exactly the same type of incinerator.