Awesome game, good story.
To the review, two below me, the invisable walls are a part of the map, and you have to get behind the dog, and shoot it in it's back.
Awesome story line though, it kinda reminds of the Ancient Greek mythology, of a man who goes into Hades and finds his wife's lost soul, but Hades told him to "never look back" and in the end, he looks back, when she's a shade, and vanishes forever. Still an awesome game, keep up the good work.