Eurogamer.com has some more details on the mini-expansion cum tech demo that is "The Lost Coast". The release will be specifically for high-end PCs, and is intended to show off the places that Valve can stretch the Source technology into. From the article: "If you jump out of a dark space into a light area you're going to be blinded. It's going to be really bright until your eyes adjust. It can be used the other way around, too. Hide from a monster in a dark area and it will take a couple of seconds to go from a silhouette to detail..."