The game looks awesome. It's what Eidos Montreal wishes they could've made.
The controls for moving around work great, and I found vaulting more forgiving than in Half Life.
However, I couldn't get the combat to work in the second stage. Enemies can't hurt me and I can't hurt them back. I even got a few of them to in-fight, and they can't kill each other either. It's the same in both the Windows and Linux version.
I can lose health from fall damage, and also heal with food just fine. The shotgun crashes the game.
Keep up the good work.