Judging by the first comment, maybe I missed something, because the first map had several bugs in it. I started out with nothing, not even the suit (is it suppoused to be like that?) I found the grav-gun, but it was only usefull for picking up stuff and destroying crates. I also found the car and an empty battery. I understood you were suppoused to charge it, somehow. I never figured it out though... so I went back to see if I missed something.
I destroyed the wooden barricade using the grav-gun and then I saw this big and wide open area. Pretty nice actually. I realized I shouldn't go that way without the car, so I went back. (I should mention that there is a loading point, right after the fences which you can crawl under).
When I came back to where the car was... the car was gone... and the battery too. So, I couldn't do anything. I went back one more time and then I walked outside. It didn't took long before I was attacked by soldiers, and killed. Then I gave up and quit the game.
One thing that confused me, was that small elevator. I think you've placed a PLAYER CLIP there, because I couldn't crawl inside it. I placed the battery in there and pressed the button and the elevator went up, but nothing more happened.
Also the cave wasn't sealed completely, so I could see the skybox in several places. And everytime I went inside that small room, the framerate dropped for some odd reason.
Sorry, but this wasn't fun at all...