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:

[Paul Graham] We wanted players to feel safe while standing in a portal, so we never kill them or destroy objects within a portal that's closing. Instead, we either push or teleport objects out of a portal as it closes.

[Robin Walker] We very deliberately introduce and train each gameplay concept in Portal, so that once players reach this spot, we're confident that they know what a portal is and roughly how it works. Early versions of the game let players stumble through the beginning without always understanding what was going on, which really compromised teaching new concepts. The puzzle you just finished was designed so that stumbling around will almost always lead to a dead end. Completing the puzzle requires walking through a minimum of five portals in a specific order. This kind of gating, in which a solid understanding of key gameplay concepts is required for success, helped standardize the learning curve of the game tremendously.