Via GameSetWatch, an article on Waxy.org highlighting the great audio commentary for Half-Life 2: Episode One. The article includes a few excerpts from the experience, via flash movies. From the article: "Most of the game's 115 nodes are audio only, pointing out interesting tidbits about the scene you're currently in, such as the visual design, character dialogue, or gameplay. Some of the best examples discuss the iterations a stage or puzzle went through, why original versions didn't live up to expectations, and how they reached their final design. It's a fascinating glimpse into the minds of the developers, very much like sitting next to them as you play through at your own pace. But a few commentary nodes do much more, taking over the player's view to show them something hidden or entirely new. I've captured video from some of my favorites." Completely worth it to play through a second time to experience.