Good game but too short.
You start outside of citadel where you are under the rocks.Dog pulls them away and you are free to see what happened with citadel.You also get your gravity gun.
This game is short...Its shorter than half life 2.But it isn't that short that you can complete with 2-3hours.And also it isn't that easy.
Your mission is to get to the train station with Alyx and escape the city 17.
Before you reach that you need to slow down the transmission inside the citadel you need to be inside some creepy tunnels what are dark and full of zombies.And you need to be in city 17 fighting with antilions,ant guards and combines to surive.