Literally the only knock on this game is that its too short. For the 2-3 hours this game last, you'll be absolutely hooked on the addicting FPS/puzzle gameplay loop and the eery vibes of the Appature Science testing facility. The whole time, everything seems normal, but you know something isnt quite right, and seeing the mystery reveal itself is incredible. Enough has been said about GLADoS, but she really is an all time video game villian. You need to play this game.