If you have played Half Life 2 you will be wanting to do the episodes. This first episode is great.
I had to look around during this and it was amazing that it really felt like I was moving down and into this building.....
My favourite part was the elevator ride down where you have to fend off falling objects and keep restarting the lift.... Fun.
My least favourite part was the carpark levels where you had to ascend through an underground carpark to the surface...... Antlions compound all this as they come through holes which you have to plug up. But it's fast and it's fun..
The end battle was good although once it's over you feel like wanting more.. But the train ride out of the city suggests more is on the way.
Excellent fun game. Highly recommend it.