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:

[Kerry Davis] This room was designed to make players understand that entrance and exit portals aren't tied to the color of the portal. Playtesters often assumed that orange portals were exit-only, so we created this puzzle to force players to enter an orange portal.

[David Kircher] When rendering the player's view through a portal, we must render a separate image using a virtual camera which looks out of the opposite portal. To obtain a correct image and efficient rendering performance, we render only what is visible through the limited field of view of the opposite portal and exclude objects which lie between the virtual camera and the plane of the opposite portal.

[Garret Rickey] The combination of portal-destroying fields (which we call 'fizzlers') and the elevators serve a dual purpose. They provide a clearly identifiable end-point for each test-chamber, while also addressing the more practical problem of how to keep players from portaling across level loads. We eventually integrated the fizzlers into several of our puzzle designs.