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:

[Chris Chin] Even though layering player training was a design goal from the start, we still ended up introducing some concepts too quickly. For instance, this used to be the first energy-ball redirection puzzle. Playtesting revealed that this puzzle introduced too many new concepts at once, which ended up frustrating a lot of playtesters. In response, we inserted two test chambers before this one to make the energy-ball redirection training more gradual.

[David Kircher] We previously talked about how we handle static portal collision. But collision with moving objects on the other side of the portal is a completely different and equally hard problem. Walking onto this scaffold was a very iffy proposition for the first few months of development. We solve the problem of colliding with these dynamic objects by cloning the objects from one portal to the other and strictly controlling what objects are allowed to collide with each other and how they're allowed to collide.